Immunofluorescent detection of a PSP‐producing dinoflagellate, Alexandrium minutum , from Bay of Plenty, New Zealand - F. H. Chang; I. Garthwaite; D. M. Anderson; N. Towers; R. Stewart; L. MacKenzie (New Zealand Journal of Marine and Freshwater Research, 1999)
In this study the cross‐reactivity of an antibody raised against cell surface antigens of Alexandrium minutum Halim, a dinoflagellate isolated from the Bay of Plenty, New Zealand, during the 1993 toxic shellfish outbreaks, was tested on other strains of the same species isolated from a variety of locations, as well as a wide range of unrelated phytoplankton using an indirect immunofluorescence staining technique. The antibody showed positive reactions to all four isolates of A. minutum from different localities in New Zealand and one from South Australia. The antibody also showed a positive, but weaker, reaction to A. ostenfeldii (two isolates) from New Zealand but no reaction with A. lusitanicum , a species which is morphologically similar to A. minutum . No cross‐reactivity was observed with 51 species or strains from 10 different algal classes tested. The antibody bound to cells of A. minutum preserved with either 2.5% glutaraldehyde or 3.5% formaldehyde. Recognition of cells in stationary growth phase, including the encysted form, however, was generally weaker than for cells growing exponentially. The cell surface location of the antigen was confirmed using confocal laser scanning microscopy.

A new size record for kahawai (Arripis trutta) from New Zealand - Clinton A. J. Duffy; Craig Petherick (New Zealand Journal of Marine and Freshwater Research, 1999)
A 790 mm fork length (FL) (6.91 kg) kahawai netted in Waitangi Estuary, Hawke Bay, New Zealand, in August 1997 is positively identified as Arripis trutta (Bloch & Schneider 1801) using meristic and morphometric characters. This fish is considerably larger than the accepted maximum length for the species from New Zealand, and was aged between 15 + and 17 years. New Zealand A. trutta of this age are normally 460–610 mm FL. Captures of kahawai greater than 640 mm FL and 4.0 kg in weight from New Zealand are reviewed, and a 10.0 kg A. trutta is tentatively identified from Northland. It is suggested that these fish may straggle to New Zealand from eastern Australia. Norfolk Island, Lord Howe Island, or Kermadec Islands.

Description of Kaniwhaniwhanus gen. n. (Diptera: Chironomidae: Orthocladiinae) from New Zealand - I. K. G. Boothroyd (New Zealand Journal of Marine and Freshwater Research, 1999)
Kaniwhaniwhanus gen. n. is described for the first time from New Zealand. Diagnoses of the male imago, pupa, and larva are presented. Kaniwhaniwhanus can be distinguished by a combination of hairy eyes, pigmented wings, presence of bare anal point, and absence of inferior volsella in the male imago; the absence of a thoracic horn, presence of anteriorly directed comb‐like hooklets on abdominal tergites TII‐TV, evenly distributed shagreen on posterior abdomen tergites, and the absence of anal macrosetae in the pupa; and by a 4‐segmented antenna, broad single tooth of mentum with four pairs of lateral teeth, and the presence of paired medio‐lateral lobes of the mentum in the larva. Kaniwhaniwhanus appears to be monotypic and is designated by the type species, Kaniwhaniwhanus chapmani . Larvae of Kaniwhaniwhanus chapmani are known from North Island streams and have been recorded from Lake Grasmere in the South Island.

Crustacean zooplankton communities in a New Zealand lake during four decades of trophic change - M. A. Chapman; J. D. Green (New Zealand Journal of Marine and Freshwater Research, 1999)
Lake Rotorua is a eutrophic polymictic lake in the centre of the North Island, New Zealand. Three studies of its crustacean zooplankton, in 1955–56, 1967–69, and 1994–95 have been made. Despite increased eutrophication since the first study, species composition has not changed: the calanoid copepod, Calamoecia lucasi , dominates for much of the year and Bosmina cf. meridionalis and Cerio‐daphnia cf. dubia are the only limnetic cladocerans. Comparison of their annual cycles in abundance between the studies show little regularity in the seasonal patterns, suggesting that stochastic events, such as storms, may be the most important controlling factors through their effects on food levels.

Sediment macrobenthos of upper Otago Harbour, New Zealand - Simon L. Grove; P. Keith Probert (New Zealand Journal of Marine and Freshwater Research, 1999)
Sediment macrobenthos of the Upper Otago Harbour, south‐eastern New Zealand, was surveyed in 1993. Replicate samples (0.1 m 2 sieved on 1 ‐mm mesh) were taken using a diver‐operated suction sampler from 15 stations, including some suspected to be contaminated. Multivariate analysis of abundance data was used to examine patterns of benthic community structure and their relationship to environmental variables: sediment grain size, organic content, heavy metal concentration (V, Cr, Mn, Co, Ni, Cu, Zn, Cd, Pb), sea‐floor temperature, dissolved oxygen concentration, water depth, and macro‐algal content. Samples from Sawyers Bay, an area previously identified as impacted by sewage and industrial waste, were set apart from all other stations. A combination of percent sand, macro‐algal content, water depth, and chromium concentration correlated best with the observed community structure.

Life history of Kaniwhaniwhanus chapmani Boothroyd (Chironomidae: Orthocladiinae): Population dynamics, emergence, and drift - I. K. G. Boothroyd (New Zealand Journal of Marine and Freshwater Research, 1999)
The life history of Kaniwhaniwhanus chapmani Boothroyd is described through examination of larval population dynamics, larval drift, and adult emergence. Development of larvae occurred all year but peak larval densities occurred in February, July, and November and indicated several generations with longest generation times in the autumn. Emergence occurred all year and a bimodal diel emergence pattern was apparent at certain times. K. chapmani larvae were present in the stream drift at all times but not in high densities, and generally only during daylight hours with an early morning/late afternoon drift pattern. K. chapmani exhibits a generally non‐seasonal life history but rapid growth tends to occur when conditions of temperature and food quality are likely to be optimal resulting in shorter generation times and peaks in larval populations.

New grenadier fishes of the genus Coryphaenoides (Pisces: Macrouridae); one from off New Zealand and one widespread in the southern Indo‐West Pacific and Atlantic Oceans - Peter J. McMillan (New Zealand Journal of Marine and Freshwater Research, 1999)
Two new species of macrourid fishes of the genus Coryphaenoides from New Zealand are described. Coryphaenoides dossenus n. sp. is widespread on the continental slope at 480–1464 m and shows sexual dimorphism with the largest male about half the length of the largest female. It is also known from the Tasman Sea, Coral Sea, Indian Ocean, and the eastern side of the Atlantic Ocean south of c. 6° S. Coryphaenoides microstomus n. sp. is known only from four specimens collected from a single station at 1550–1720 m off the east coast of the North Island, New Zealand.

Mouthpart morphology of three calanoid copepods from Australian temporary pools: Evidence for carnivory - John D. Green; Russell J. Shiel (New Zealand Journal of Marine and Freshwater Research, 1999)
The mandibles, first and second maxillae, and maxillipeds of Boeckella major, B. pseudo‐chelae , and Hemiboeckella searli from temporary pools of the upper River Murray catchment were dissected off and examined by light microscopy for features associated with carnivorous feeding. In B. major adaptations for carnivory are enlarged ventral mandibular teeth, strong falciform medial setae on the second maxillae, falciform endopodal setae on the maxilliped, large body size and large mouthpart size in relation to body size. Its mandibular edge index is 772, in the upper omnivore range. B. major is predicted to be an omnivore with strong carnivorous tendencies and able to handle large prey items. Carnivorous features in H. searli are enlarged ventral mandibular teeth, a mandibular edge index of 1395, and strong unguiform and falciform setae on the second maxillae. It is predicted to be an omnivore with moderate carnivorous tendencies, but unable to handle prey as large as can B. major . In B. pseudochelae the only adaptations for carnivory are an edge index of 1080 and falciform setae on the maxilliped. It is predicted to be an omnivore with herbivorous tendencies. Examination of gut contents confirmed these predictions. B. major guts contained 19 animal taxa, mainly planktonic cladocerans, copepods and rotifers, H. searli 12 taxa, mainly copepods and rotifers, and B. pseudochelae 8 taxa, mainly rotifers. All had consumed algae. We suggest that predation by B. major may be an important factor affecting community structure in fishless Australian temporary pools.

Antarctic orca in New Zealand waters? - Ingrid N. Visser (New Zealand Journal of Marine and Freshwater Research, 1999)
I report on a group of orca ( Orcinus orca (Linnaeus, 1758)) near the Bay of Islands, New Zealand, which were a lighter coloration than orca usually seen in these waters. Differences in pigmentation included a light grey caudal peduncle area and a dorsal cape, which has previously only been described for Antarctic orca. The size and shape of the eye patches were not consistent with orca photo‐identified in New Zealand. I suggest that this group of orca, although observed in New Zealand waters, were of Antarctic origin.

Seasonal abundance of small cladocerans in Lake Mangakaware, Waikato, New Zealand - Tracey L. Greenwood; John D. Green; Brendan J. Hicks; M. Ann Chapman (New Zealand Journal of Marine and Freshwater Research, 1999)
The seasonal changes in the dynamics and life histories of the Cladocera in Lake Mangakaware, North Island, New Zealand, were studied over 19 months by sampling at weekly or 2‐weekly intervals. Lake Mangakaware is a 13.3 ha polymictic lake with high nutrient status, low Secchi disc transparencies, and an unstable thermal regime. The four planktonic cladoceran species ( Bosmina longirostris, B. meridionalis, Ceriodaphnia pulchella , and C. dubia ) exhibited disjunct population maxima. Only B. longirostris was perennially present. All species exhibited low fecundities and low lipid content, indicating that food resources were limited and that competitive interactions and resistance to starvation were probably important in determining species success. Increases in body size in cooler seasons were unrelated to clutch size, giving further support for the view that available food was limited. These results are consistent with previous experimental findings that subtle differences in life history can determine seasonal success and the outcome of competition between similar species.

Phytoplankton distribution and oyster, Ostrea chilensis (Philippi 1845), growth at Putemún Channel, southern Chile - Jorge E. Toro; Pamela I. Paredes; Dario J. Villagra (New Zealand Journal of Marine and Freshwater Research, 1999)
The phytoplankton community of the Putemun Channel (southern Chile) and its correlation with some environmental variables is analysed in this paper. Samples were collected on a monthly basis from May 1991 to May 1993. A total of 121 phytoplanktonic species were identified. The phytoplankton cell abundance ranged between 3.5 × 10 4 cells/litre and 11.2 × 10 6 cells/litre. The phytoplankton community was characterised by the dominance of diatoms. An inverse relationship between temperature and species diversity was observed. A significant correlation, after excluding tychoplank‐tonic benthic forms, was found between chlorophyll a , cell abundances, and temperature. The influence of biotic and abiotic variables on oyster ( Ostrea chilensis (Philippi 1845)) growth was analysed. The instantaneous growth rate was found to be positively correlated with both temperature and phytoplankton abundance, whereas significant negative correlation between growth and amount of particulate inorganic matter was found.

Dietary alterations in resident and migratory New Zealand common smelt ( Retropinna retropinna ) in lower Waikato lakes after two decades of habitat change - T. G. Northcote; M. A. Chapman (New Zealand Journal of Marine and Freshwater Research, 1999)
The diets of lake resident and both allopatric and sympatric migratory (diadromous) forms of common smelt ( Retropinna retropinna (Richardson)) in Lakes Waahi and Whangape (Lower Waikato River system, New Zealand) were examined before and after collapse of macrophyte beds and loss of associated invertebrates. Before this diets were varied, but dominated by chironomid larvae and pupae, supplemented by semiplanktonic crustaceans in small smelt in particular and by corixids in larger smelt. Afterwards diets were less diverse and the main food items were mysid shrimps. The opportunistic, generalist feeding habits of smelt help their survival of habitat changes.

Size at maturity and seasonal changes in gonad activity of yellowtail kingfish (Seriola lalandi; Carangidae) in New South Wales, Australia - B. M. Gillanders; D. J. Ferrell; N. L. Andrew (New Zealand Journal of Marine and Freshwater Research, 1999)
Gonad development, seasonal changes in gonad activity, and size at maturity were investigated in female and male yellowtail kingfish ( Seriola lalandi; Carangidae) collected from New South Wales, Australia between August 1995 and June 1996. Kingfish displayed peak gonad activity in December suggesting a summer spawning period. Males matured at smaller sizes than females. Females first matured at 698 mm fork length (FL) and 3+ years, but 50% maturity was not attained until 834 mm FL. The smallest recorded mature male was 360 mm FL and the estimated size at which 50% of males were mature was 470 mm FL (+ years). Many female fish are harvested prior to first reproduction, but the impact of this on the stock remains unclear.

Allozyme variation in scampi ( Metanephrops challengeri ) fisheries around New Zealand - P. J. Smith (New Zealand Journal of Marine and Freshwater Research, 1999)
Scampi ( Metanephrops challengeri Balss, 1914) support a significant fishery in New Zealand waters. Allozyme analysis of samples from four fishery areas found a low level of genetic variation but significant heterogeneity in allele frequencies. There were significant differences between samples from the Auckland Island Shelf and those from mainland New Zealand at three loci, but only one locus showed heterogeneity among mainland samples.

Predicting rates of primary production in the vicinity of the Subtropical Convergence east of New Zealand - Mark Gall; Ian Hawes; Philip Boyd (New Zealand Journal of Marine and Freshwater Research, 1999)
Water column integrated productivity of phytoplankton in three water masses east of New Zealand (Subtropical, Subtropical Convergence, and Subantarctic) varied both seasonally and spatially, ranging across two orders of magnitude. Productivity was highest in spring and autumn, and lowest in winter. Subtropical and Convergence waters were generally more productive than Subantarctic waters, but during summer the 2–3‐fold range of production was similar in each of the three water masses. Multiple regression analysis identified that most of the variability in production was associated with differences in integrated chlorophyll a concentrations (56%). By considering both surface chlorophyll a and incident irradiance we derived a relationship which explained 74% of observed spatial and seasonal variability in integrated production. These surface variables can be sensed remotely, suggesting the potential for broad spatial mapping of the seasonal cycles of production in these water masses in the New Zealand Exclusive Economic Zone (NZEEZ). Further analysis of the relationship identified that most of the remaining variability could be attributed to p b opt (a temperature‐dependent photo‐adaptive term). Exceptions to the relationship and the application of productivity models within NZEEZ are discussed.

Ann Chapman–inspirational limnologist - John Green; Ian Boothroyd (New Zealand Journal of Marine and Freshwater Research, 1999)

A fish out of water: Observations on the ability of black mudfish, Neochanna diversus , to withstand hypoxic water and drought - J. D. McPhail (New Zealand Journal of Marine and Freshwater Research, 1999)
The ability of black mudfish ( Neochanna diversus Stokell) to withstand hypoxia and drought was examined by observing an isolated population near Hamilton, New Zealand over the course of a year (September 1988‐November 1989). In addition, a series of experiments were performed to determine what dissolved oxygen levels trigger air‐breathing in the black mudfish, and the length of time this species can survive out of water in a humid environment. Air‐breathing behaviour in black mudfish involves rising to the surface, gulping an air bubble and holding the bubble in the buccal cavity while the fish continues gill ventilation. Water in the study drain started to become hypoxic in mid November and by early December oxygen levels were ‐1 on the surface and ‐1 near the bottom (15 cm deep). In the laboratory, at water temperatures ranging from 20 to 22°C, none of the 20 test fish gulped air from the surface until oxygen levels dropped below 2.5 mg litre ‐1 ; c. 45% of the animals began air‐gulping at oxygen levels between 2.0 and 2.5 mg litre ‐1 and, at oxygen levels below 1.0 mg litre ‐1 , 100% of the test fish gulped air from the surface. Over a similar temperature range, animals were kept on damp moss for 10 weeks (the drought duration in the drain was 132 days). Under these conditions, test animals lost weight steadily: adults lost 17–24%, and young‐of‐the‐year 30–45%, of their initial weight. On re‐immersion, all adults recovered; however, two young‐of‐the‐year fish died. Within 4 h of re‐immersion, the surviving fish increased their body weight by 6–12%, but within 24 h they returned to their pre‐immersion weight. The mechanisms involved in drought resistance in black mudfish (and their relevance to conservation and habitat preservation) are discussed. A possible option for the restoration, and maintenance, of mudfish in habitats formerly occupied by this species complex is to provide appropriate drought shelters while maintaining a regime of seasonal drought to remove competitors.

Albatross predation of juvenile southern blue whiting ( Micromesistius australis ) on the Campbell Plateau - Yves Cherel; Sue Waugh; Stuart Hanchet (New Zealand Journal of Marine and Freshwater Research, 1999)
Dietary samples collected at Campbell Island in summer 1997 indicate that southern blue whiting ( Micromesistius australis ) formed the bulk of the food of black‐browed albatrosses ( Diomedea melanophrys impavida ) during the chick‐rearing period. Birds preyed upon a single size class of fish with a mode at 80–90 mm standard length; fish were 4–5 months old and belonged to the + age group. Satellite tracking showed that, when performing trips of short duration, adult albatrosses foraged within the 1000 m depth contour in the subantarctic zone north of Campbell Island. The feeding ecology of albatrosses thus suggests that juvenile (+) southern blue whiting are pelagic and occur in dense schools in the top 5 m of the water column over the Campbell Plateau during the summer months. The high reliance of birds on juvenile southern blue whiting during the chick‐rearing period has implications for the management of the southern blue whiting fishery and the conservation of black‐browed albatrosses and other marine predators occurring in the New Zealand subantarctic area.

Land use in the Taupo catchment, New Zealand - N. B. Edgar (New Zealand Journal of Marine and Freshwater Research, 1999)
This paper describes current initiatives to develop a lake management plan for Lake Taupo, New Zealand. Recently there has been an indication that a shift from dry stock farming to large‐scale dairy farming will occur in the Taupo catchment. The local community has expressed an interest in this shift towards more intensive land use. There is public concern regarding the current state of Lake Taupo's water quality and the ability to maintain environmental quality in the face of increasing development pressures. Concerns about rising levels of nutrients in the lake are supported by trend analysis of lake water quality monitoring data. The Taupo District Council and the Waikato Regional Council have proposed development of a Lake Taupo Management Plan. A number of mechanisms for achieving this process could be explored. These include a plan largely developed by an inter‐agency management group or a more public participatory approach directly involving the community. A general lake planning framework is described and some of the limitations of the process explored. Comparison with experiences at Lake Rotorua, New Zealand, and Lake Tahoe, United States of America, supports a pre‐cautionary approach to the use of predictive ecological models in policy development. The inability of aquatic ecological theory to conform to quantitative approaches in other physical sciences needs to be acknowledged by scientists and conveyed to the public. Until the link between land‐use practice and water quality is better understood, a pre‐cautionary approach to catchment development at Lake Taupo should be encouraged. One cannot assume that common desires for both environmental protectionism, and progressive intensification of land use, will lead to sustainable resource management. The environmental effects of dairy farming indicate that encouraging this land‐use practice will not lead to the desired community expectation of water quality protection at Lake Taupo.

Egg and larval development of laboratory‐reared striped trumpeter latris lineata (forster in bloch and schneider 1801) (percoidei: Latridiidae) from Tasmanian waters - Dianne M. Furlani; Frances P. Ruwald (New Zealand Journal of Marine and Freshwater Research, 1999)
Description of striped trumpeter (Latris lineata (Forster in Bloch and Schneider 1801)) eggs and larvae, previously described in summary only, is provided and illustrated from laboratory‐reared material. Laboratory fertilised eggs are round, 1.26–1.44 mm diameter, with a single, pigmented oil globule 0.27–0.29 mm diameter in an unsegmented yolk. Early‐stage embryos are pigmented on trunk and tail dorso‐laterally, forming a dorsal and ventral pigment band in late‐stage embryos. Hatching occurs 7–8 days post‐fertilisation in 12°C. Larvae are 2.8–3.5 mm body length (BL) at hatching with a voluminous finfold, large yolk sac with centrally‐placed oil globule, distinct pigmentation pattern, and no head spines. Flexion occurs from 5.6 to 8.7 mm BL. Fin formation commences from 6.6 mm BL in the sequence caudal, dorsal and anal (simultaneously), pectorals and pelvics. Myomeres number 33–39. Larvae are pigmented predominantly on the head, dorsal and ventral surfaces of trunk and tail, and gut ventrally, with melanophores also on upper and lower jaws. Larvae survived to 45 days post‐fertilisation, 11.9 mm BL, with complete fin‐formation of the caudal fin only. Similarities are noted between L. lineata larvae and aplodactylid, bovichtid, cheilo‐dactylid, chironemid, sillaginid, and tetragonurid larvae. A small number of L. lineata larvae were also caught inshore and at shelf edge on the Tasmanian west coast in late winter/early spring (September/ October).

Recruitment and distribution of juvenile salmonids in Lake Coleridge, New Zealand - Eric Graynoth (New Zealand Journal of Marine and Freshwater Research, 1999)
Rainbow trout (Oncorhynchus mykiss Richardson) and chinook salmon (O. tshawytscha Walbaum) fry and + fingerlings entered Lake Coleridge, a deep, oligotrophic lake in the Southern Alps of New Zealand, in spring and early summer and dispersed throughout the shallow littoral. In contrast, most juvenile brown trout (Salmo trutta Linnaeus) remained in the tributaries for 1–2 years before migrating down stream to the lake. Juvenile salmonids ( 150 mm) and adult salmon and rainbow trout (>210 mm). The abundance of + rainbow trout in the littoral zone declined rapidly from February to August and stocks were supplemented by a migration of yearling fish from the tributaries in spring. The shallow littoral zone and tributaries are both important for juvenile trout rearing in this lake.

Attenuation and transport of atrazine and picloram in an alluvial gravel aquifer: A tracer test and batch study - Liping Pang; Murray E. Close (New Zealand Journal of Marine and Freshwater Research, 1999)
A natural‐gradient tracer experiment and laboratory batch tests were conducted to study attenuation and transport of atrazine and picloram in an alluvial gravel aquifer. An analytical transport model, AT123D, was used to analyse the field data. Data analysis suggests that there was no retardation and degradation of atrazine and picloram in the aquifer over a distance of 90 m within a period of 49 h. In the batch tests with a much longer time duration (194 days), atrazine concentrations significantly decreased and picloram concentrations showed a small decrease. It is considered that the rapid decrease in atrazine levels in the first 2 days was sorption‐dominated and the slow decrease subsequently was mainly because of degradation and partially the result of slow sorption. If it is assumed that the decrease in the first 2 days was all the result of sorption and it had reached equilibrium, the estimated K d values are 0.04 ml/g for atrazine, and 0.02 ml/g for picloram. Rates of atrazine degradation estimated from the data after 2 days (slow rate of decrease) are 3.4 × 10 ‐3 per day (equivalent half‐life 204 days), and 3.0 × 10 ‐3 per day (equivalent half‐life 231 days), for total and chemical degradation, respectively, assuming that there was no adsorption after 2 days. No degradation rate could be determined from the picloram data of the batch tests because of its highly noisy data and insignificant decrease in concentrations. The significantly higher attenuation parameters derived from the batch tests compared to those derived from the field data suggests that attenuation of pesticides in the field is affected by other factors, such as aquifer heterogeneity and preferential flow, and flow hydrodynamics etc., which should be taken into account when applying laboratory‐derived values to the field conditions.

First New Zealand record of the Australian bridled goby, arenigobius bifrenatus (Pisces: Gobiidae) - Trevor J. Willis; Justine E. H. Saunders; Danielle L. Blackwood; Jeffrey E. Archer (New Zealand Journal of Marine and Freshwater Research, 1999)
Arenigobius bifrenatus (Kner 1865) is a burrowing coastal and estuarine goby from temperate areas of Australia. One specimen was captured from the Whangateau Harbour, north‐eastern New Zealand, on 1 April 1998, constituting the first record of this species from New Zealand. Further intensive beach seining at Pollen Island, within the Waitemata Harbour (Auckland), yielded two further specimens which were females in breeding condition. We suggest that the species is an adventive, and its presence in northern New Zealand waters is the result of accidental transport in shipping ballast water.

Effects of sewage contamination on macro‐algae and shellfish at Moa point, New Zealand using stable carbon and nitrogen isotopes - Karyne M. Rogers (New Zealand Journal of Marine and Freshwater Research, 1999)
Stable carbon and nitrogen isotopes have been used to characterise sewage discharge and effects on seaweed (Ulva lactuca L.), blue mussels ( Mytilus galloprovinialis) , and limpets (Cellana denticulata) from Moa Point Bay, New Zealand. The nitrogen ( 15 N/ 14 N) ratio is shown to be a good tracer of sewage pollution in Ulva lactuca and associated grazers ( Cellana denticulata) as a result of the increased contribution of urea and ammonia to the surrounding marine environment from the sewage outfall. The carbon ( 13 C/ 12 C) ratio is suggested as a more appropriate sewage tracer for mussels (Mytilus galloprovinialis) , which filter feed the particulate organic matter from the effluent. Lower carbon : nitrogen ratios were found in U. lactuca sampled from the outfall region, compared to uncontaminated control sites, however carbon: nitrogen ratios do not vary significantly amongst shellfish species.

Cover preference tests of juvenile shortfinned eels (Anguilla australis) and longfinned eels (A. dieffenbachii) in replicate channels - G. J. Glova (New Zealand Journal of Marine and Freshwater Research, 1999)
The day‐time cover preferences of three size groups (small = (Anguilla australis) and longfinned eels (A. dieffenbachii) were tested during summer in replicate channels provided with natural (macro‐phytes, woody debris, cobbles) and artificial (shade, plastic pipes) cover types. Tests on the longitudinal distribution of all three size groups of shortfinned eel (with no cover in the channels) revealed no significant bias in the distribution of small and medium eels, but did so for large eels which favoured the ends of the channels. Similar bias occurred in the actual cover preference tests, which was adjusted for by the Poisson log‐linear model used in analysing the data. When the species were tested separately, small and medium eels of both species preferred cobbles and macrophytes more or less equally, whereas large eels showed a clear preference for macrophytes and a minor attraction for cobbles. When tested together, species cover preferences differed significantly, with a greater proportion of all sizes of longfins in the cobbles and shortfins in the macrophytes and woody debris. Artificial cover was an unattractive alternative to natural cover for all sizes of both species of eel. The results of these experiments suggest that both size and species interactions influence the distribution of juveniles of both species in the wild.

Date and age at migration in juvenile giant kokopu, Galaxias argenteus (Gmelin) (Teleostei: Galaxiidae) and estimation of spawning season - R. M. McDowall; G. R. Kelly (New Zealand Journal of Marine and Freshwater Research, 1999)
Juveniles of giant kokopu (Galaxias argenteus (Gmelin)) that had newly entered fresh water were captured, primarily from the Buller and Hokitika Rivers, New Zealand, between 5 November and 15 December (when sampling ceased). Age at migration estimated from otolith daily growth rings was mostly c. 104–140 days. There is a positive relationship between fish length and number of otolith growth rings at migration, though variation is broad. Back calculation to hatch indicated that hatching occurred 185–245 days after 1 January (4 July‐2 September); allowing 28 days for development, these data suggest that giant kokopu spawn between early June and early August.

Preliminary estimates of mass‐loss rates, changes in stable isotope composition, and invertebrate colonisation of evergreen and deciduous leaves in a Waikato, New Zealand, stream - Brendan J. Hicks; J. Lee Laboyrie (New Zealand Journal of Marine and Freshwater Research, 1999)
Rates of mass loss are important in the choice of tree species used in riparian rehabilitation because leaves that break down fast should contribute to stream food‐webs more rapidly than leaves that break down more slowly. To examine comparative mass‐loss rates of some native evergreen and introduced deciduous trees in a New Zealand stream, fallen leaves were incubated in bags with 2×3 mm mesh openings. The native trees were mahoe (Melicytus ramiflorus) , kahikatea (Dacrycarpus dacrydioides) , silver beech ( Nothofagus menziesii) , rewarewa (Knightia excelsa) , tawa (Beilschmiedia tawa) , and the introduced trees were silver birch (Betula pendula) and alder (Alnus glutinosa) . The leaf bags were left in the Mangaotama Stream for 28 days from mid April to mid May 1995 when mean water temperature was 14.5°C, giving a total of 406 degree days. Rates of mass loss followed the sequence: mahoe > silver birch > alder > kahikatea > silver beech > rewarewa > tawa. Mean mass‐loss rate for mahoe, assuming a negative exponential model, was 0.0507 k day ‐1 (0.00350 k (degree day) 1 ), and for tawa was 0.0036 k day ‐1 (0.00025 k (degree day) 1 ). C:N ratio decreased on average from 45:1 to 35:1, and δ 15 N increased between 0.7 and 3.0‰ (1.8 ± 0.41%o, mean ±1 standard error), excluding kahikatea. Changes in δ 13 C were smaller and not consistent in direction. Biomass of invertebrates was greatest in bags that had lost 25–45% of their initial leaf biomass.

Seasonal arrival patterns of juvenile freshwater eels (Anguilla spp.) in New Zealand - D. J. Jellyman; B. L. Chisnall; M. L. Bonnett; J. R. E. Sykes (New Zealand Journal of Marine and Freshwater Research, 1999)
The arrival season of glass eels of both New Zealand species of freshwater eel, the short‐finned eel (Anguilla australis (Richardson)) and the longfmned eel (A. dieffenbachii (Gray)), was studied by electric fishing of 13 streams/rivers throughout east and west coasts of both North and South Islands at 14‐day intervals. Sites were usually located at the most downstream riffle exposed at low tide, and sampled by single‐pass electro fishing. The species composition was dominated by shortfins, with exceptions being west coast sites, one in the North Island and two in the South Island. From a comparison of species proportions in adjacent catchments, it was concluded that glass eels make choices about entry in particular water‐types. As the stage of pigmentation advanced during the arrival season, “early stage” glass eels were defined and densities of these compared to show seasonal arrival patterns—densities were generally low in August, highest in September‐October, and declined during November‐December. Patterns of arrival varied from almost continuous in some streams to “intermittent” in others. Longfmned glass eels preceded shortfinned glass eels, and probably arrived in the North Island before the South Island; shortfinned glass eels showed the opposite trend. Possible migration routes to New Zealand are discussed.

Factors affecting settlement and early post‐settlement survival of the New Zealand abalone Haliotis australis - Graeme A. Moss (New Zealand Journal of Marine and Freshwater Research, 1999)
This paper describes studies on the settlement of the abalone Haliotis australis Gmelin. Ten‐day‐old H. australis larvae had a slower rate of settlement than 5‐day‐old larvae. A high proportion of veliger larvae had the ability to prolong the searching phase of settlement and delay metamorphosis, even over prepared settlement surfaces but radula development continued at a similar rate in both settled and swimming larvae. In any one batch of larvae settlement was slow and asynchronous and post‐settlement survival was low. Light was shown to influence the swimming behaviour of larvae in settlement tanks, with more larvae swimming in the dark than in the light. The implications of these behaviours are discussed in relation to larval and post‐larval energetics and feeding.

Transition from pasture to native forest land‐use along stream continua: Effects on stream ecosystems and implications for restoration - Mike R. Scarsbrook; Jane Halliday (New Zealand Journal of Marine and Freshwater Research, 1999)
Three first‐order, hill country, pasture streams in Waikato, New Zealand, were chosen to investigate the effects of patches of late‐succession indigenous riparian forest on water quality, epilithon, stream morphology, and aquatic macro‐invertebrates. Sites were situated in open pasture and at two distances (c. 50 and 300 m) into a forest remnant on each stream. Shade, channel width, and epilithon biomass were restored to conditions similar to a native forest control site within 300 m of the streams entering the native forest remnants, whereas water chemistry and levels of surficial fine sediment changed more slowly. Invertebrate community composition showed shifts towards the native forest condition just 50 m into the forest remnants, and full recovery had occurred within 300 m. Results from this study suggest that discontinuous restoration of riparian margins could mitigate some changes associated with pastoral land use, but sediment and water quality problems may not be solved.

External forcing by wind and turbid inflows on a deep glacial lake and implications for primary production - Marc Schallenberg; Mark James; Ian Hawes; Clive Howard‐Williams (New Zealand Journal of Marine and Freshwater Research, 1999)
Lake Coleridge is a deep monomictic lake in the Southern Alps of New Zealand which is affected by strong adiabatic winds. It receives significant inputs of inorganic suspended solids from rivers diverted into the lake for hydro‐electric generation. External inputs of wind energy and suspended solids to Lake Coleridge were quantified throughout 1 year and their impacts on hydrodynamics and the light climate were analysed. During stratification, the lake had a deep mixed layer, underlain by a complex metalimnion. High wind energy inputs caused large internal waves which resulted in the upwelling of hypolimnetic water, horizontal density gradients, and significant currents. Calculated vertical diffusivity and exchange coefficients were similar to those of much larger lakes. Analyses indicated that mixing in the metalimnion was often a result of shear stresses arising from vertical gradients in horizontal velocities. Whole lake total suspended solids (TSS) burdens were significantly correlated with the previous 13‐week integrated TSS loading from inflows. A seasonal pattern was observed where TSS from inflows entered either below, within or above the metalimnion. Evidence of effects of sediment resuspension from the marginal lake bottom was observed only when the lake level was low and the resulting impacts on the light climate were minimal. The synergistic effects of climate, thermal structure, and inflows resulted in the apparent light‐limitation of phytoplankton photosynthesis in winter months.

Measuring photosynthetic characteristics of the seagrass Syringodium isoetifolium: Implications for in situ productivity estimates - Peter C. Pollard (New Zealand Journal of Marine and Freshwater Research, 1999)
The rates of photosynthesis of the seagrass Syringodium isoetifolium (Aschers.) Dandy were measured by a gas‐release technique with whole shoots incubated in the field. Greater than 95% of the variation of the photosynthetic data could be accommodated by the Photosythesis‐Irradiance (PI) model presented here. As expected, the shape of the Pi‐curves differed between shoots. The different shapes resulted from the different photosynthetic maxima and the efficiency with which shoots used light but not the amount of light required by the shoot to reach saturating light intensities. Irrespective of the units (whole shoot, leaf chlorophyll content, or leaf surface area) used to generate the PI‐curves, there was no significant (P > 0.05) difference between saturating light intensities (I k ), the mean value was 180 ± 33 μmol m ‐2 s ‐1 . The quantity and quality of light available to these plants can modify leaf surface and chlorophyll content of seagrass shoots. Presenting the rates of photosynthesis as a function of chlorophyll or leaf surface area diminishes the ability to observe differences between plants. Hence, the health of seagrass plants may be more obvious and quantifiable if seagrass productivity data are expressed as a function of whole seagrass shoots rather than on the basis of chlorophyll content or leaf surface. During the 20‐day study, the photoperiod ranged from 6.2 to 10.8 h and gross productivity estimates ranged from 10 to 18 g C day ‐1 m ‐2 . These estimates were more than 10 times greater than the in situ net leaf daily productivity of 0.9 g C day ‐1 m ‐2 that was measured with a traditional leaf marking technique. This result implies that most of the production was directed below ground. The health of seagrasses is related to the productivity of the whole plant not just the tissue that appears above ground. In comparative studies that are used to determine the habitat requirements of seagrasses and the impacts of pollutants on seagrass survival whole plant productivity measurements would appear to provide a better indicator of seagrass health.

Spatial variation in litter production by the mangrove Avicennia marina var. australasica in Rangaunu harbour, Northland, New Zealand - Jonathan D. May (New Zealand Journal of Marine and Freshwater Research, 1999)
Litter fall was measured at two intertidal levels within two stands of the mangrove Avicennia marina (Forsk.) Vierh. var. australasica (Walp.) Moldenke in Rangaunu Harbour, New Zealand (34° 57'S, 173° 15'E). The seasonal pattern of litter fall was typical of A. marina at high latitudes. Flowering occurred in March‐April and fruit fell 9 months later during December‐January. Leaf fall was highest from November to February and was positively correlated with temperature and negatively correlated with sediment water availability (total rainfall minus total evaporation). Total annual litter fall ranged from 1.81 ha ‐1 yr ‐1 to 6.21 ha ‐1 yH and was proportional to mean tree height at each site. Leaves constituted on average 73% of the total litter fall and were the only litter component to show significantly lower magnitude at both elevated sites. The largest litter collections were made during the summer months coincident with peak falls of leaves and fruit. The possible contribution of mangrove litter to es‐tuarine food chains in northern New Zealand estuaries is discussed.

Habitat preferences of shortfinned eels (Anguilla australis) , in two New Zealand lowland lakes - D. J. Jellyman; B. L. Chisnall (New Zealand Journal of Marine and Freshwater Research, 1999)
The habitats used by shortfinned eels (Anguilla australis (Richardson)) in Lakes Ellesmere (Canterbury) and Waahi (Waikato), New Zealand, were determined using a variety of capture techniques during the summers of 1994/95–1997/98. The most successful technique used to catch juvenile eels ( 300 mm) preferred sandy substrates, but showed no marked preference for particular depths or distances offshore. The spatial distribution of both size groups was non‐random. Although water temperature did not influence catch rates (CPUE, catch‐per‐unit‐effort) of either size group, catches of the smaller eels were greater during the new moon phase than during the other phases—catches of larger eels were unaffected by lunar phase. Length‐frequency distributions of eels from Lake Ellesmere were strongly bimodal, with eels 200–300 mm poorly represented—this probably reflects poor recruitment for several years, either because lake opening times did not coincide with the availability of glass eels, or because overall numbers of glass eels were low. Juvenile eels in Lake Waahi, caught in fine‐meshed fyke nets and in special brush collectors, were also inshore residents; unlike Lake Ellesmere, juvenile eels could be caught at the lake margins, probably because Lake Waahi is not subject to the same wind‐induced water level fluctuations as Lake Ellesmere. Recruitment into Lake Waahi commenced in mid December, but there was evidence of low recruitment in past years for this lake also. An important outcome of this research is that estimates of the number of juvenile eels to be transplanted during stocking programmes should be made using the area of the shallow littoral rather than the area of the whole lake.

Photographic identification of the New Zealand sea lion: A new technique - Shaun D. McConkey (New Zealand Journal of Marine and Freshwater Research, 1999)
Photographic identification of individuals, a standard technique in the study of whales and dolphins, has seldom been attempted in pinniped studies. Photographs of damage and abnormalities in fore and hind flippers facilitated individual identification of almost 80% of individuals encountered during a 3‐year study of New Zealand sea lions (Phocarctos hookeri) at the Otago Peninsula. Lower canine size and large body scars were also useful in identifying individuals. None of the features used to identify the 48 individuals in this study changed sufficiently to hinder positive identification. Especially in small populations, the method has several advantages over traditional tagging.

New species of benthopelagic copepods of the genus Stephos (Calanoida: Stephidae) from Wellington Harbour, New Zealand - Janet M. Bradford‐Grieve (New Zealand Journal of Marine and Freshwater Research, 1999)
Two new species of benthopelagic calanoid Copepoda are decribed from Evans Bay, Wellington Harbour, New Zealand. The species Stephos hastatus n. sp. and S. angulatus n. sp. (Family: Stephidae) are the first records of this family and genus from New Zealand.

Measuring woody debris in the small streams of New Zealand's pine plantations - Brenda R. Baillie; Tina L. Cummins; Mark O. Kimberley (New Zealand Journal of Marine and Freshwater Research, 1999)
To assess the impact of harvesting on woody debris volumes in streams, a method was required with sufficient precision to provide meaningful evaluation and comparison of pre‐ and post‐harvest levels of woody debris. Before harvest, woody debris volumes were measured in 24 first‐ to third‐order stream sites in New Zealand's mature pine plantations (22–34 years of age). An adaptation of the Van Wagner line intersect method was used to measure the small woody debris 1–9 cm in diameter (SWD). All large woody debris ≥10 cm in diameter (LWD) was measured for diameter and length. Woody debris volumes in the stream channel ranged from 2 to 345 m 3 ha ‐1 , averaging 112 m 3 ha ‐1 (±34, 95% confidence interval (CI)). Woody debris surface areas averaged 2883 m 2 ha ‐1 (±688), range 220–6769 m 2 ha ‐1 . Most of the woody debris volume (87%) was composed of LWD. Sixty‐seven percent of the woody debris volume was located above the stream, the remainder was lying in‐stream or on the floodplain. Woody debris volumes in streams of mature pine plantations in New Zealand were similar to woody debris volumes in streams of temperate native forests in New Zealand and North America. These sites will be remeasured after harvest to identify any changes in woody debris characteristics.

A new grenadier, genus Caelorinchus , from Australia and New Zealand (Pisces, Gadiformes, Macrouridae) - Tomio Iwamoto; Peter McMillan; Yuri N. Shcherbachev (New Zealand Journal of Marine and Freshwater Research, 1999)
A new species, Caelorinchus trachycarus , is described from continental slope depths of 622–1350 m off New Zealand, southern Australia, and the Norfolk Ridge south of New Caledonia. The modified scales of head ridges is especially spiny, more so than in any other member of the genus. The blackish fins, dark overall coloration, prominent free neuromasts on the head, and the numerous parallel rows of spinules on body scales distinguish the new species from the closely similar and sympatric C. acanthiger . It differs from C. parallelus and C. kermadecus by its naked nasal fossa, snout length, and scale spinulation, among other characters.

Background and review of ageing orange roughy (Hoplostethus atlanticus , Trachichthyidae) from New Zealand and elsewhere - D. M. Tracey; P. L. Horn (New Zealand Journal of Marine and Freshwater Research, 1999)
Studies on New Zealand orange roughy (Hoplostethus atlanticus) otoliths, and of orange roughy ageing conducted in New Zealand and elsewhere are described. Ageing studies have concentrated on three aspects: the interpretation of daily growth increments, the interpretation of annual growth increments, and radiometric analyses. All the methods suffer from problems relating to validation. Daily growth zones have not been validated, annual zones have been validated for juvenile fish only, and assumptions necessary for the application of radio‐metric techniques may be flawed. However, the weight of current evidence indicates that orange roughy are a slow‐growing, long‐lived species. A review of otolith morphology and microstructure studies, and a summary of the productivity parameters used in stock assessments of orange roughy, are also presented. Standard protocols used to prepare and interpret otoliths in current investigations are described. This review highlights the complexities of ageing long‐lived, deepwater fish, and stresses the importance of obtaining accurate productivity parameters for stock assessment. The key area for future research is the age validation of post‐juvenile fish, which should lead to the development of an accurate ageing technique.

Effects of land use on native fish communities in east coast streams of the North Island of New Zealand - David K. Rowe; Ben L. Chisnall; Tracie L. Dean; Jody Richardson (New Zealand Journal of Marine and Freshwater Research, 1999)
The community structure, density, and biomass of native fish species was determined for first‐ to second‐order streams draining mature pine, native forest, and pasture catchments in seven, North Island, New Zealand, east coast rivers or streams. Multiple‐pass electric fishing was used to determine fish densities, and differences in fish community structure between land uses were detected using non‐metric multi‐dimensional scaling analysis. Species responsible for changes in fish community structure were identified by comparing species densities between land uses. Six fish species occurred commonly within each drainage system and although there was no difference in fish community structure between streams in native or exotic forest, differences occurred between the fish communities of forested and pastoral streams. Pastoral streams contained more shortfinned eels (Anguilla australis) , more inanga (Galaxias maculatus) , and fewer banded kokopu (Galaxias fasciatus) than forested streams. Fish biomass was also higher in pastoral streams. We concluded that the type of forest (mature exotic pine versus mixed‐species indigenous) had little effect on the native fish populations, but that pasture supported an increased fish density and biomass due mainly to increases in shortfinned eels. There were fewer banded kokopu in pasture than in forested streams, but exotic forest streams contained as many banded kokopu as native forest streams.

Movement of hapuku ( Polyprion oxygeneios ) determined from tagging studies - M. P. Beentjes; M. P. Francis (New Zealand Journal of Marine and Freshwater Research, 1999)
Hapuku (Polyprion oxygeneios) were tagged in south‐east South Island (SESI), Cook Strait (CS), and Poor Knights Islands (PKI), New Zealand, to determine their movements. 1623 fish were tagged and the overall recapture rate was 16.3%. Some hapuku were recaptured from the tagging sites (SESI 13%, CS 39%, PKI 40%), often after long periods at liberty, whereas others travelled substantial distances. The greatest distance travelled was 1389 km (by two fish) and the maximum period at liberty was 10.2 years. SESI hapuku tended to migrate northwards towards CS. The median distance travelled increased with hapuku length at recapture, suggesting that maturation and spawning stimulate migration. However, some of the smaller, immature hapuku also travelled several hundred kilometres. CS hapuku appeared to travel much shorter distances than SESI hapuku, but this may have been an artifact of the lower hapuku fishing effort outside the CS‐Kaikoura region. PKI hapuku showed very limited movements, and no interaction with CS or SESI fish. The results are consistent with the presence of a single stock in the SESI‐CS region, and possibly a separate stock in northern New Zealand.

Spawning site selection by two galaxiid fishes, Galaxias anomalus and G. depressiceps , in tributaries of the Taieri River, South Island, New Zealand - Suzanne J. Moore; Richard M. Allibone; Colin R. Townsend (New Zealand Journal of Marine and Freshwater Research, 1999)
Recent studies have led to the recognition of Galaxias depressiceps and reinstatement of Galaxias anomalus . The two species maintain near allopatric distributions and it has been suggested that spawning habitat availability, at least partially, controls the distribution of these species. The spawning habitat of each species was determined and an assessment of the influence of spawning habitat availability on the distribution of the two species was carried out. Factors that may have influenced the onset of spawning were also examined. We found that G. depressiceps selected spawning sites with a high proportion of boulder substrata and nests were found on the underside of or between boulders. G. anomalus spawned within the streambed substrata, under boulders or cobbles, in shallow water and narrow channels relative to the available habitat. Suitable boulder spawning substratum for G. depressiceps in the G. anomalus sites was limited and this supports the hypothesis that spawning habitat availability influences G. depressiceps distribution. Conversely G. anomalus spawning habitat was available in G. depressiceps streams, indicating that spawning habitat limitations are not restricting G. anomalus . The onset of spawning, for both species, did not appear to be related to daylight, phase of the moon, or stream water level, but all species started spawning as water temperatures rose. The proximity of G. anomalus spawning sites to the stream edge and their occurrence in poorly consolidated substrata presents two management issues. Water abstraction may expose spawning sites if stream water levels are lowered, and these sites are vulnerable to trampling by stock.

Responses of seven species of native freshwater fish and a shrimp to low levels of dissolved oxygen - Tracie L. Dean; Jody Richardson (New Zealand Journal of Marine and Freshwater Research, 1999)
The tolerances of seven New Zealand freshwater fish species and one species of shrimp to low levels of dissolved oxygen were determined in the laboratory by holding fish at dissolved oxygen levels of 1, 3, or 5 mg litre ‐1 for 48 h at 15°C. Juvenile rainbow trout (Oncorhynchus mykiss) were also tested for comparison. All of the banded kokopu whitebait (Galaxias fasciatus) , juvenile torrentfish (Cheimarrichthys fosteri) , adult and juvenile common smelt (Retropinna retropinna) , juvenile common bully (Gobiomorphus cotidianus) , and trout were dead after 48 h exposure to 1 mg litre ‐1 . Adult and juvenile inanga ( Galaxias maculatus ), adult common bully (Gobiomorphus cotidianus) , and shrimp (Paratya curvirostris) had mortalities ranging from 27 to 80% at 1 mg litre ‐1 , whereas all of the elvers ( Anguilla spp.) survived. Juvenile rainbow trout were the most sensitive of the species tested, and the only species that had mortalities during exposure to 3 mg litre ‐1 . No deaths of any fish occurred at 5 mg litre ‐1 . Time to 50% mortality at 1 mg litre ‐1 for common smelt (adult and juvenile) and juvenile common bully were similar to those for juvenile rainbow trout. Most fish moved towards the surface within the first few hours of exposure to 1 mg litre ‐1 . Rainbow trout was the only species that showed consistent surfacing behaviour at 3 mg litre ‐1 and rarely were fish observed to move towards the surface at 5 mg litre ‐l . Within the limits of the lifestages and species tested, adequate protection is provided for native fish by adopting the United States Environmental Protection Agency dissolved oxygen criteria for salmonid waters.

Animal and human faecal pollution in New Zealand rivers - A. M. Donnison; C. M. Ross (New Zealand Journal of Marine and Freshwater Research, 1999)
Sentinel freshwater mussels (Hydridella menziesi) were immersed in rivers at sites impacted by faecal pollution. The indicator bacterium, Escherichia coli , was recovered from all mussels including those at a forest control site, but concentrations were highest at sites impacted by either treated sewage or treated meat‐processing waste water, or by inputs from dairy farms. The three pathogens sought were recovered from mussels, except those at the forest (control) site: Campylobacter jejuni and Campylobacter coli at treated sewage sites; Salmonella typhimurium and C. jejuni at treated meat‐processing waste water sites; and C. jejuni and Yersinia enterocolitica at sites impacted only by dairy farms. The FRNA bacteriophage concentration was high in mussels impacted by sewage or sheep‐processing waste water but was low when the input was only from dairy farms. Mussels up to 23 km from a sewage discharge contained a high concentration of FRNA suggesting that there could be a health risk due to viruses, although the water did not exceed recommended guidelines. Pathogens were also sought in untreated waste waters. C. jejuni and C. coli were recovered from both sheep‐processing and beef‐processing waste waters and the only sewage isolate identified was confirmed as C. coli. Salmonella spp. were recovered from all waste waters, with S. typhimurium phage type 135, isolated from a sample of meat‐processing waste water, and from mussels immersed 1 and 5 km down stream of that plant's discharge. Y. enterocolitica was recovered from most samples of animal waste water. It appears that pathogens are introduced into New Zealand rivers by all major sources of faecal contamination.

Spawning, settlement, and growth of the New Zealand venerid Ruditapes largillierti (Philippi 1849) in culture - Greg N. Kent; Greg B. Maguire; Ian Duthie; Richard Pugh (New Zealand Journal of Marine and Freshwater Research, 1999)
Spawning, larval rearing, and growout of Ruditapes largillierti (Philippi 1849) were investigated in a series of trials conducted at the University of Tasmania (UTAS), Launceston and Georges Bay, St Helens, Tasmania, Australia. Intramuscular injection of serotonin (3 × 10 ‐7 to 1.5 × 10 ‐6 moles) failed to induce spawning in female Ruditapes largillierti , although some males did spawn. Fecundity of R. largillierti induced to spawn by thermal stimulus ranged from 0.5 to 0.9 × 10 6 eggs female ‐1 . Fertilised eggs developed into trochophore larvae by 24 h at 20°C and D veligers with a mean shell length of 85.3 ± 4.7 μm within 48 h. Early larvae were frequently deformed and their mortality rates were very high. Development to pediveliger stage (mean shell length 200.3 ± 7.3 μm) took between 11 and 16 days at 20°C, and metamorphosis to spat (mean shell length 240 (μm) occurred between Days 16 and 19. There was no significant difference in efficacy of epinephrine, norepinephrine, or untreated groups for inducing larval settlement. Average growth of juveniles held subtidally within trays or baskets (mesh size 1.7–12.0 mm) was 1.3 mm month ‐1 . The aquaculture potential of this subtidal venerid clam warrants further investigation.

Movement of rainbow trout ( Oncorhynchus mykiss ) during the spawning migration in the Tongariro River, New Zealand - M. Dedual; I. G. Jowett (New Zealand Journal of Marine and Freshwater Research, 1999)
The movements of 74 rainbow trout (Oncorhynchus mykiss) were monitored every 2–3 days using radio‐telemetry during the spawning migration up the Tongariro River, New Zealand, between June and November 1995. Contrary to the views of anglers, movements of individual fish were highly variable and upstream movement could not be predicted from environmental conditions and fish related variables (length, sex, and reproductive status). There was no significant difference in individual movement between male and female fish. When individual movements were in an upstream direction, maiden trout moved faster, but less often, than fish that had spawned in previous years. The flow in the lower river explained 9% of the variance in individual downstream movements. Net upstream movement occurred throughout most of the study period with above mean activity when the river was in spate, especially early in the migration season when fish responded to flow changes as low as 7%. Above mean upstream daily movement occurred 8 times on rising and 9 times on falling barometric pressure. Large floods caused downstream displacements, but fish tended to move up stream again on the flow recession. The most noticeable downstream movement occurred following the eruption of Mount Ruapehu.

Movements of the New Zealand school shark, Galeorhinus galeus , from tag returns - Rosemary J. Hurst; Neil W. Baglet; Graeme A. McGregor; Malcolm P. Francis (New Zealand Journal of Marine and Freshwater Research, 1999)
During the period March 1985 to January 1997, 3950 school sharks, Galeorhinus galeus (L), were tagged, mostly opportunistically during other research activities. Up to July 1997, 207 sharks had been recaptured. The best recovery rates were from sharks tagged with internal (8.8%) and dart (6.5%) tags and first caught by line methods (22%). The maximum distance travelled was 4940 km, the maximum time at liberty was 3505 days (9.6 years), and greatest average speed was 22.8 km/day. Most sharks (76%) moved less than 500 km, but the larger movements included 10% of sharks which had travelled over 1700 km to southern Australia. The proportion of sharks recaptured in their home Quota Management Areas (QMA) was 53% overall. However, the distance travelled increased significantly with time at liberty. After 2 years at liberty, only 22% of sharks were recaptured within a release QMA and 23% were recaptured in Australia. These findings suggest that future assessment of school shark fisheries within New Zealand waters should consider the species as one stock with a relatively high emigration rate to Australian waters.

Dye‐marking of New Zealand black‐browed and grey‐headed albatrosses from Campbell Island - S. M. Waugh (New Zealand Journal of Marine and Freshwater Research, 1998)
The foraging zones used by two species of albatross, breeding at Campbell Island, were studied by dye‐marking breeding birds in 2 years in combination with ship‐board observations of bird distribution. New Zealand black‐browed albatross, Diomedea melanophrys impavida , were found mainly over the shelf waters of the Campbell Plateau and the south‐eastern South Island mainland, but were also found over oceanic waters to the south of the Campbell Plateau as far south as 65°S. Possible inter‐annual variability was noted, with birds found in the Chatham Rise area in one year but not another. Dyed grey‐headed albatross, D. chrysto‐stoma , were not seen by observers, although it is unclear whether this is because of differential behaviour between the species or differences in visibility between dyes.

Stage‐dependent thyroxine effects on sea urchin development - Leland G. Johnson (New Zealand Journal of Marine and Freshwater Research, 1998)
Thyroxine, one of the iodinated hormones produced by vertebrate thyroids, has been reported to accelerate late larval development in several sea urchins (Chino et al. 1994) and in the crown‐of‐thorns starfish (Johnson & Cartwright 1996), but thyroxine effects on earlier portions of echinoderm development have not been reported. I investigated thyroxine effects on developmental rates during several periods spanning development from early cleavage to metamorphosis in the New Zealand sea urchin Evechinus chloroticus (Valenciennes). Thyroxine treatment slowed development between the eight‐cell stage and assembly of the four‐armed pluteus and mid‐larval development between the four‐armed and six‐armed stages. Thyroxine treatment accelerated progress of eight‐armed plutei toward settling, but did not alter the final percentages of larvae that settled and metamorphosed to juvenile urchins. Acceleration of late larval echinoderm development by thyroxine may indicate a relatively ancient evolutionary origin of thyroxine's effects on developmental processes (Johnson 1997).

Stream lighting in five regions of North Island, New Zealand: Control by channel size and riparian vegetation - Robert J. Davies‐Colley; John M. Quinn (New Zealand Journal of Marine and Freshwater Research, 1998)
Lighting of streams profoundly influences their ecology, particularly through primary production and thermal behaviour. We used paired canopy analysers, instruments with fish‐eye lens imaging, to measure sunlight exposure of streams in five regions of North Island, New Zealand. Reach‐averaged stream lighting, at both water and bank level, was strongly influenced by riparian vegetation type. Pasture streams had comparatively high light exposure (median water level lighting = 45% of ambient), with most shading contributed by banks and overhanging herbs. Lighting was low in small forest streams (median = 1.3% for native forest, 1.2% for pine plantations), but increased sharply as the gap in the canopy widened with increase in channel width above c. 3.5 m. The understorey in pine plantations contributed more shade than the pines themselves: damage to this understorey (e.g., by goat browsing or floods) increased lighting markedly. Harvesting of pine plantations exposed streams to high light levels except where a riparian buffer was maintained. Periphyton biomass, varying over more than four orders of magnitude in the study streams, correlated broadly with lighting.

Influences of stream size and catchment land‐use on fine particulate organic matter retention in streams - Niall Broekhuizen; John M. Quinn (New Zealand Journal of Marine and Freshwater Research, 1998)
Using corn pollen as an analogue for fine particulate organic matter (FPOM), retention characteristics were measured for 13 reaches encompassing three different catchment land‐use classes (pasture, native forest, and exotic pine forest), and five pasture sites along the Mangaotama Stream, New Zealand. The retention coefficients (specific loss rate, m ‐1 ) of reaches having similar positions in the stream continuum did not differ significantly between land‐use types. The retention coefficient was strongly related to several correlates of position in the stream continuum—notably the logarithm of discharge. We were unable to identify the mechanisms responsible for removing corn pollen from suspension, but loss rates were consistently lower than those predicted from the still‐water sinking speeds of the corn pollen.

Freshwater bryozoans of New Zealand: A preliminary survey - Timothy S. Wood; Lisa J. Wood; Gaby Geimer; Jos Massard (New Zealand Journal of Marine and Freshwater Research, 1998)
Five bryozoan species were encountered in a 15‐day survey of freshwater habitats in New Zealand. Listed in order of decreasing frequency these were: Fredericella sultana, Plumatella repens, P. emarginata, Paludicella articulata , and one plumatellid species not previously described. Micro‐structural features of the floatoblast annulus separate the P. repens specimens into two distinct varieties, named here P. repens typica and P. repens rugosa. Paludicella , reported almost 100 years ago from the City of Dunedin waterworks, was still found only in a single reservoir of that city. Species distribution did not correlate significantly with water temperature, current velocity, pH, or total dissolved solids. Two additional species believed to occur in New Zealand, Fredericella australiensis and Plumatella fungosa , were not seen in this brief survey. An identification key is provided for New Zealand bryozoans.

Phytoplankton assemblages and photosynthetic pigments during winter and spring in the Subtropical Convergence region near New Zealand - F. Hoe Chang; Mark Gall (New Zealand Journal of Marine and Freshwater Research, 1998)
The distribution of phytoplankton on both the east, in the region near the Subtropical Convergence (STC), and the west coast of South Island, New Zealand was investigated in winter and spring 1993. Water samples were analysed for the cell carbon biomass, species composition, and pigment characteristics. In both winter and spring, the overall biomass/standing stocks consistently were greatest in the STC, intermediate in the subtropical (ST) both on the west (ST(W)) and east (ST(E)) coasts, and the least in the subantarctic (SA) waters. In spring, organic cell carbon and chlorophyll a measured in the STC were up to 6‐fold greater than in winter. In the STC in both seasons, phytoplankton assemblages were dominated by diatoms, and these species were more similar to those found in ST than in SA waters. The domination of diatoms in phytoplankton assemblages in the STC is consistent with the predominance of fucoxanthin observed in this region. The highest diatom concentrations (both in terms of cell carbon and chlorophyll a ) detected during the spring bloom in the STC were located either at 10 m below the surface, or below the euphotic zone (close to the bottom of mixed layer depth). The most abundant diatom species recorded in both winter and spring in the STC were Lauderia annulata and Nitzschia/Pseudo‐nitzschia spp. In ST waters dinoflagellates and diatoms were dominant in winter and spring respectively. To the south in both winter and spring, however, small‐celled nanoflagellates were dominant in the high nutrient and low chlorophyll (HNLC) SA waters. The domination of nanoflagellates in SA waters in both seasons corresponded well with the predominance of indicative pigments (viz., 19'‐hexanoyl‐oxyfucoxanthin, 19'‐butanoyloxyfucoxanthin, and diadinoxanthin). The generally shallower, nutrient‐rich (NO 3 ‐ , 5–12 (imol litre ‐1 ) waters over Chatham Rise in the STC provides a relatively stable water column, and is suggested to support high abundance of diatoms. Low concentrations of dissolved reactive silicate (DRSi) and the build‐up of diatoms observed in the STC in spring implied DRSi limitation.

Identification of potentially toxic Pseudo‐nitzschia (Bacillariophyceae) in New Zealand coastal waters, using lectins - Lesley L. Rhodes (New Zealand Journal of Marine and Freshwater Research, 1998)
Identification of species within the do‐moic acid‐producing diatom genus Pseudo‐nitzschia is vital for biotoxin monitoring and decisions regarding shellfish harvesting, particularly when blooms are occurring. Several Pseudo‐nitzschia species produce high concentrations of domoic acid per cell, whereas others are non‐toxic, but all have similar morphologies using standard brightfield light microscopy. FITC‐conjugated lectins discriminated between the New Zealand derived species tested in this study, except for P. delicatissima and P. pseudo‐delicatissima . These results differ from those reported for Pseudo‐nitzschia species isolated from Galician (Spanish) waters, which suggests variability in production of surface sugars by these diatoms depending on geographical origin and/or environmental conditions. Ribosomal RNA‐targeted oligo‐nucleotide probes, at present being field trialled in several countries including New Zealand and the United States, are therefore still the preferred method of Pseudo‐nitzschia species identification underpinning New Zealand's biotoxin risk assessment programmes.

Neocyttus psilorhynchus, a new oreosomatid (Pisces, Zeiformes) from southern Australia and New Zealand, with redescriptions of its congeners - G. K. Yearsley; P. R. Last (New Zealand Journal of Marine and Freshwater Research, 1998)
The oreosomatid genus Neocyttus contains five valid species of which three are named: N acanthorhynchus Regan, 1908 (southern Indian Ocean), N. helgae (Holt and Byrne, 1908) (North Atlantic Ocean), and N. rhomboidalis Gilchrist, 1906 (circumglobal in Southern Ocean). These species are redescribed based on the types and new material. A fourth, from southern Australia and New Zealand, is described herein as N . psilorhynchus n. sp. Additional specimens are required for a full description of a fifth species provisionally identified as Neocyttus sp. (northeastern Indian Ocean). N. psilorhynchus n. sp. is distinguished from its described congeners by the following combination of characters: 16–18 pectoral‐fin rays; mid‐opercle with 14–17 low, radiating ridges; supraorbit and lachrymal terminating in a forward‐projecting extension or rugosity covered with a dense cluster of robust nodular spinules; body scales extremely adherent, spinoid usually with about seven, but up to 11, long, sharp, very compressed spines (slightly conical in subadults) in single elevated row along posterior margins; soft dorsal‐ and anal‐fin bases with, respectively, 28–30 and 25–28 greatly enlarged scales; naked snout; and a moderately deep belly. A key to Neocyttus species is included.

Evaluation of Enterolert ® for the enumeration of enterococci in the marine environment - Stan Abbott; Brian Caughley; Guy Scott (New Zealand Journal of Marine and Freshwater Research, 1998)
Current methods for the analyses of enterococcal densities include the membrane filtration (MF) technique and the multiple tube fermentation technique for the most probable number (MPN). Both techniques are labour intensive, tedious, and require a minimum of 48–72 h before results can be obtained. The Enterolert ® system, designed to detect enterococci in water in 24 h, uses 4‐methylumbelliferyl‐ß‐D‐glucoside as a defined substrate nutrient indicator. This compound, when hydrolysed by enterococcal‐ß‐glucosidase, releases 4‐methylumbelliferone which exhibits fluorescence under a UV 365 lamp. In this study 343 marine water samples from selected sites in the Wellington area of New Zealand were tested to evaluate the sensitivity and specificity of Enterolert in parallel with the MF method. Statistical analysis of parallel test results showed a strong linear correlation ( r = 0.927) and no significant difference between the two methods by paired Mest analysis ( P = 0.39). Based on the 2.4% false positive and 0.3% false negative rates, Enterolert was found to have a sensitivity of 99.8% and a specificity of 97.0%. Activity‐costing analyses revealed that the variable cost per test was less for Enterolert (NZ$18.33) than MF (NZ$22.79). Significant time savings are achieved because Enterolert requires less time than MF for reagent preparation, sample set‐up, incubation, and reading of tests. The results from this study suggest that more widespread use of this new technology in marine water quality monitoring is warranted, since rapid tests mean that monitoring agencies can respond to sudden increases in enterococci numbers more quickly and can therefore take immediate corrective action to ensure the safety of users of recreational waters.

Submerged vegetation of Lakes Te Anau, Manapouri, Monowai, Hauroko, and Poteriteri, Fiordland, New Zealand - Rohan D. S. Wells; John S. Clayton; Mary D. de Winton (New Zealand Journal of Marine and Freshwater Research, 1998)
The submerged vegetation in Lakes Te Anau, Manapouri, Monowai, Hauroko, and Poteriteri from the South Island of New Zealand, was surveyed in 1993 using SCUBA methods to record a range of botanical parameters to the deepest extent of the vegetation. This is the first detailed account of the submerged vegetation in these lakes and the first description for Lake Poteriteri. The vegetation of these lakes is comprised predominantly of native species. Isoetes kirkii dominates the shallow‐water assemblage in all lakes. Hydatella inconspicua , an endemic shallow‐water plant of rare status, is reported for the first time in the South Island, New Zealand. Formerly only reported from a limited number of North Island sand dune lakes, the discovery of these southern disjunct populations of H. inconspicua means that this species should no longer be considered endangered. The tall‐growing native vascular species, Potamogeton cheesemanii, Myriophyllum propinquum , and M . triphyllum were recorded in all five lakes. The most frequent tall vascular species in Lakes Te Anau, Manapouri, and Monowai was the adventive Elodea canadensis , which was not recorded in Lakes Hauroko or Poteriteri. Juncus bulbosus , another, adventive species, was recorded in all lakes except Lake Te Anau. The most abundant group of plants within all five lakes were native charophytes. Chara fibrosa was the species with greatest cover in Lakes Hauroko and Poteriteri, whereas Chara corallina was in the other lakes. Bryophytes were the deepest vegetation recorded and were widespread but not abundant within all the lakes. The bottom depth limits of the vegetation ranged from 7.5 to 19 m, with Lake Hauroko, the clearest lake, having the deepest vegetation.

Silverstream eco‐hydraulics flume: Hydraulic design and tests - V. I. Nikora; D. G. Goring; B. J. F. Biggs (New Zealand Journal of Marine and Freshwater Research, 1998)
Hydraulic design details are presented of the Silverstream eco‐hydraulics flume, which is a 12 m long by 75 cm wide tilting outdoor flume situated on the left bank of the Silverstream River, 30 km north of Christchurch, New Zealand. Results of testing, both mechanical and hydraulic, are presented and discussed. The mechanical adjustments required to accommodate the weight of water in the flume and thermal expansion and contraction of the frame (exacerbated by being outside) are described. Hydraulic calibration experiments using Acoustic Doppler Velocimetry indicate that there is a central portion at least 4 m long by 15–20 cm wide of the flume where the flow is uniform and 2‐dimensional. Regions up stream and down stream of this area are affected by entrance and exit conditions. Close to the side walls, cells of helical secondary currents were found, and these appear to be separated from the zone of 2‐dimensional flow by narrow regions with anomalous turbulence properties. The “frozen” turbulence hypothesis was proven true by the calibration experiments. These findings can have implications in eco‐hydraulic experiments on organism‐flow interactions, mass transfer, and uptake processes.

An observation of the turbellarian Paravortex sp. in the New Zealand scallop Pecten novaezelandiae (Bivalvia: Pectinidae) - C. M. C. Woods; B. J. Hayden (New Zealand Journal of Marine and Freshwater Research, 1998)
In a novel association the turbellarian rhabdocoel Paravortex sp. was observed in a group of the scallop Pecten novaezelandiae . Flatworms were more frequently observed in gaping and dead scallops, although the average density of flatworms in infested scallops was low. Scallops which were non‐gaping contained very few flatworms. Flatworms occurred throughout the entire digestive system of the scallops with the majority found in the intestine.

Mollusca: the southern synthesis. Fauna of Australia, Volume 5. Edited by PamBeesley, GrahamRoss, and AliceWells. Published in 1998 by CSIRO Publishing, Melbourne, Australia. 2 volumes (Parts A and B), 1234 p. ISBN: 0–643–05754–0. Price: A$295, available from: CSIRO Publishing, P. O. Box 1139, Collingwood, Vic 3066, Australia; sales@publish.csiro.au (in New Zealand: Manaaki Whenua Press, P. O. Box 40, Lincoln, Canterbury; comfortg@landcare.cri.nz).Marine invertebrates of southern Australia. Part III. Edited by S. A.Shepherd & M.Davies. Published in 1997 by the South Australian Research and Development Institute (Aquatic Sciences) and the Flora and Fauna of South Australia Handbooks Committee. 363 p. ISBN: 1–876007–04–4. Price: A$49.00 (contact: SARDI, P. O. Box 120, Henley Beach, SA 5022, Australia).Coral reef fishes. By EwaldLieske and RobertMyers. Published in 1997 by Princeton University Press, 41 William Street, Princeton, New Jersey 08540, United States. 400 p. ISBN: 0–691–02659–9. Price: US$35 (United States and Canada), (email: mary_kate@pupress.princeton.edu) - Alan Beu; Steve de C. Cook; Melita Samoilys (New Zealand Journal of Marine and Freshwater Research, 1998)

Landscape Analysis of Tiger Distribution and Habitat Quality in Nepal - James L. David Smith; Sean C. Ahern; Charles McDougal (Conservation Biology, 1998)

Inference Methods for Spatial Variation in Species Richness and Community Composition When Not All Species Are Detected - James D. Nichols; Thierry Boulinier; James E. Hines; Kenneth H. Pollock; John R. Sauer (Conservation Biology, 1998)
Inferences about spatial variation in species richness and community composition are important both to ecological hypotheses about the structure and function of communities and to community‐level conservation and management. Few sampling programs for animal communities provide censuses, and usually some species in surveyed areas are not detected. Thus, counts of species detected underestimate the number of species present. We present estimators useful for drawing inferences about comparative species richness and composition between different sampling locations when not all species are detected in sampling efforts. Based on capture‐recapture models using the robust design, our methods estimate relative species richness, proportion of species in one location that are also found in another, and number of species found in one location but not in another. The methods use data on the presence or absence of each species at different sampling occasions (or locations) to estimate the number of species not detected at any occasions (or locations). This approach permits estimation of the number of species in the sampled community and in subsets of the community useful for estimating the fraction of species shared by two communities. We provide an illustration of our estimation methods by comparing bird species richness and composition in two locations sampled by routes of the North American Breeding Bird Survey. In this example analysis, the two locations (and associated bird communities) represented different levels of urbanization. Estimates of relative richness, proportion of shared species, and number of species present on one route but not the other indicated that the route with the smaller fraction of urban area had greater richness and a larger number of species that were not found on the more urban route than vice versa. We developed a software package, COMDYN, for computing estimates based on these methods. Because these estimation methods explicitly deal with sampling in which not all species are detected, we recommend their use for addressing questions about species richness and community composition. Métodos de Inferencia sobre Variación Espacial en la Riqueza de Especies y la Composición de Comunidades Cuando la Totalidad de las Especies no es Detectada Las inferencias sobre variación espacial en la riqueza y composición de especies en comunidades son importantes tanto para el planteamiento de hipótesis ecológicas sobre la estructura y función de comunidades como para la conservación y manejo a nivel de comunidad. Pocos programas de muestreo de comunidades de animales proveen censos y usualmente algunas especies de las zonas muestreadas no son detectadas. Por lo tanto, los conteos de especies detectadas subestiman el número de especies presentes. Presentamos estimadores útiles para establecer inferencias sobre la riqueza comparativa de especies y la composición de especies entre diferentes localidades de muestreo cuando no todas las especies presentes son detectadas por los esfuerzos del muestreo. Nuestros métodos estiman la riqueza relativa de especies, la proporción de especies en una localidad y que son localizadas también en otra localidad y el número de especies encontradas en una localidad pero no en otra, en base a modelos de diseño robusto de captura‐recaptura. Los métodos utilizan datos de la presencia y ausencia de cada especie en diferentes ocasiones de muestreo (o diferentes localidades). Para estimar el número de especies no detectadas en ninguna ocasión (o localidad). Esta aproximación permite estimar el número de especies en la comunidad muestreada, así como en fragmentos de la comunidad, mismos que son útiles para la estimación de la fracción de especies compartidas por dos comunidades. Proveemos una ilustración de nuestros métodos de estimación al comparar la riqueza de especies de aves y su composición en dos localidades muestreadas por el Estudio de Rutas de Aves Reproductoras de Norteamérica (North American Breeding Bird Survey). En este ejemplo, las dos localidades ( y las comunidades de aves asociadas) representan diferentes niveles de urbanización. Estimaciones de la riqueza relativa, proporción de especies compartidas y el número de especies presentes en una ruta pero ausentes en otra, indicaron que la ruta con la fracción más pequeña de área urbana tuvo una riqueza mayor y un número mayor de especies no fueron encontradas en la ruta con más espacio urbano. Desarrollamos un paquete de cómputo, COMDYN, para determinar estimaciones basadas en estos métodos. Debido a que estos métodos de estimación pueden lidiar con muestreos en los cuales no todas las especies son detectadas, recomendamos su uso para abordar preguntas sobre la riqueza y composición de especies en comunidades.

Apostrophe to the Ocean - James T. Carlton (Conservation Biology, 1998)

Evaluating the Biotic Integrity of Watersheds in the Sierra Nevada, California - Peter B. Moyle; Paul J. Randall (Conservation Biology, 1998)
We developed a watershed index of biotic integrity that used whole watershed variables for metrics rather than site‐specific variables. We used the index to evaluate the biological health of 100 watersheds in the Sierra Nevada of California. The index scores, which were based on various measures of distribution and abundance of native fish and frogs, indicated that 7 of the watersheds were in excellent condition (high biotic health), 36 were in good to very good condition, 48 were in fair condition, and 9 were in poor condition. The biggest factors contributing to low index scores were large dams and introduced fishes, although measures of road density and indicators of intensity of use of terrestrial habitats were also important. Large areas of the Sierra Nevada that were once fishless now contain trout in most waters, anadromous fishes are excluded from many streams from which they were once abundant, assemblages of native fishes have been disrupted, and ranid frogs have been extirpated from many areas. All watersheds in the Sierra Nevada have thus experienced loss of biotic integrity, but some have suffered much less than others. Evaluations of the biotic integrity of watersheds over wide regions can help managers set priorities for watershed‐oriented systems of aquatic conservation and provide starting places for more‐intensive studies. Evaluación de la Integridad Biótica de Cuencas Acuíferas en la Sierra Nevada, California Un indice de cuencas de integridad biótica fue desarrollado, el cual utilizó variables paramétricas en vez de variables de lugar específico. El índice fue utilizado para evaluar la salud biológica de cien cuencas en la Sierra Nevada de California. El muestreo, el cual fue basado en varias medidas de disribución y abundancia de peces nativos y ranas indicaron que siete de las cuencas estaban en excelente condición (salud biótica), treinta y seis estaban de buena a muy buena condición, cuarenta y ocho estaban en favorable condición y nueve estaban en mala condición. Los factores más grandes que contribuyeron al bajo muestreo fueron represas grandes y peces introducidos, aunque medidas de densidad de carreteras, indicadores de intensidad del uso de comunidades terrestres, fueron también importantes. Grandes areas de la Sierra Nevada que no tenían peces ahora contienen trucha en la mayoria de sus aguas, peces anadromos están excluidos de muchos arroyos, en los cuales ellos fueron una vez abundantes; comunidades de peces nativos han sido interrumpidas, y ranas de la familia ranidae han sido exterminadas de muchas areas. Todas las cuencas en la Sierra Nevada, por lo tanto, han experimentado pérdida de integridad biótica, pero algunas han experimentado menos pérdida que otras. Evaluaciones de la integridad biótica de cuencas sobre regiones extensas pueden ayudar a establecer prioridades para un sistema de conservación acuática y proveer información básica para estudios más intensos.

Graduate Students as an Untapped Resource for Public Outreach - David Giblin; Rich Pagen (Conservation Biology, 1998)

Edge-Related Nest Predation in Clearcut and Groupcut Stands - David I. King; Richard M. DeGraaf; Curtice R. Griffin (Conservation Biology, 1998)

Distribution of Alkaloid-Rich Plant Species in Shortgrass Steppe Vegetation - Donald L. Hazlett; Neil W. Sawyer (Conservation Biology, 1998)

Conservation of the Grassy White Box Woodlands: Effects of Remnant Population Size on Genetic Diversity in the Allotetraploid Herb Microseris lanceolata - Suzanne M. Prober; Linden H. Spindler; A. H. D. Brown (Conservation Biology, 1998)

Present and Future Taxonomic Selectivity in Bird and Mammal Extinctions - Gareth J. Russell; Thomas M. Brooks; Michael M. McKinney; C. Gregory Anderson (Conservation Biology, 1998)

Effects of Rock Climbing on Cliff Plant Communities at Joshua Tree National Park, California - Richard J. Camp; Richard L. Knight (Conservation Biology, 1998)

Evaluating the Biotic Integrity of Watersheds in the Sierra Nevada, California - Peter B. Moyle; Paul J. Randall (Conservation Biology, 1998)

Population Persistence, Pollination Mutualisms, and Figs in Fragmented Tropical Landscapes - Nick A. Mawdsley; Stephen G. Compton; Robert J. Whittaker (Conservation Biology, 1998)

Management Costs for Endangered Species - David S. Wilcove; Linus Y. Chen (Conservation Biology, 1998)

1998 Society for Conservation Biology (Conservation Biology, 1998)

Obstacles to Protecting Marine Biodiversity through Marine Wilderness Preservation: Examples from the New England Region - Tatiana Brailovskaya (Conservation Biology, 1998)
The amount of terrestrial protection achieved for biodiversity through designation of no‐take public wilderness areas in the United States is much greater than no‐take protection in the nation’s National Marine Sanctuary System. With the exception of a small area in the Florida Keys, no permanent reserve in the United States protects marine biodiversity from commercial fishing with gear that has strong effects on marine habitats and which has been identified as one of the major threats to marine biodiversity. A recent national poll has shown that public support does exist for conservation of the marine environment and protection of marine biodiversity. The New England region provides examples of the obstacles that such support may face in regions with a long history of commercial exploitation of marine species. I discuss the overall influence that the commercial fishing industry in New England has had on marine conservation efforts in the region, contrast the public’s perception of marine versus terrestrial wildlife species, and describe the nature of the media’s coverage of the commercial fishing industry and fisheries management issues in the region. I propose the creation of a national no‐take marine wilderness preservation system as a way to achieve protection of marine biodiversity as a separate goal from sustainable fisheries management in New England and other, similar regions in the United States. Obstáculos para la Protección de la Biodiversidad Marina Mediante la Preservación de la Vida Silvestre: Ejemplos de la Región de Nueva Inglaterra La cantidad de protección para la biodiversidad terrestre alcanzada a través de la designación de áreas públicas de “no‐toma” de vida silvestre en los Estados Unidos es mucho mayor que aquella en las zonas de “no‐toma” del Sistema de Santuarios Nacionales Marinos. Con la excepción de un área pequeña en los cayos de Florida ninguna reserva permanente de los Estados Unidos protege la biodiversidad marina de la pesca comercial con equipos que tienen fuertes efectos en los hábitats marinos y los cuales han sido identificados como una de los mayores amenazas a la biodiversidad marina. Una encuesta nacional reciente ha mostrado que existe soporte público para la conservación del ambiente marino y la protección de la biodiversidad marina. La región de Nueva Inglaterra provee ejemplos de los obstáculos que dicho soporte enfrentaría en regiones con una historia larga de explotación comercial de especies marinas. Discuto la influencia global que la industria de la pesquería de Nueva Inglaterra ha tenido sobre los esfuerzos de conservación marina en la región, contrasto la percepción del público de las especies de vida silvestre marina comparadas con las terrestres y describo la naturaleza de la cobertura de los medios sobre asuntos relacionados con la industria pesquera y el manejo de pesquerías en la región. Propongo la creación de un sistema de preservación nacional de “no‐toma” de la vida silvestre marina como una forma para obtener protección de la biodiversidad marina como una meta separada del manejo sustentable de pesquerías en Nueva Inglaterra y otras regiones similares de los Estados Unidos.

Letters - E. N. Anderson; Brian R. Warren; Jesús A. Rivas; William Z. Lidicker; Gary K. Meffe; Reed F. Noss; Susan K. Jacobson (Conservation Biology, 1998)

1998 Society for Conservation Biology (Conservation Biology, 1998)

Do Habitat Corridors Provide Connectivity? - Paul Beier; Reed F. Noss (Conservation Biology, 1998)
Skeptics have questioned the empirical evidence that corridors provide landscape connectivity. Some also have suggested dangers of corridors. We reviewed published studies that empirically addressed whether corridors enhance or diminish the population viability of species in habitat patches connected by corridors. A randomized and replicated experimental design has not been used—and we argue is not required—to make inferences about the conservation value of corridors. Rather, studies can use observational or experimental analyses of parameters of target populations or movements of individual animals. Two of these approaches hold the greatest promise for progress, especially if the shortcomings of previous studies are remedied. First, experiments using demographic parameters as dependent variables—even if unreplicated—can demonstrate the demographic effects of particular corridors in particular landscapes. Such studies should measure demographic traits before and after treatment in both the treated area (corridor created or destroyed) and an untreated area (habitat patches isolated from one another). This approach is superior to observing the demographic conditions in various landscapes because of the tendency for corridor presence to be correlated with other variables, such as patch size, that can confound the analysis. Second, observations of movements by naturally dispersing animals in fragmented landscapes can demonstrate the conservation value of corridors more convincingly than can controlled experiments on animal movement. Such field observations relate directly to the type of animals (e.g., dispersing juveniles of target species) and the real landscapes that are the subject of decisions about corridor preservation. Future observational studies of animal movements should attempt to detect extra‐corridor movements and focus on fragmentation‐sensitive species for which corridors are likely to be proposed. Fewer than half of the 32 studies we reviewed provided persuasive data regarding the utility of corridors; other studies were inconclusive, largely due to design flaws. The evidence from well‐designed studies suggests that corridors are valuable conservation tools. Those who would destroy the last remnants of natural connectivity should bear the burden of proving that corridor destruction will not harm target populations. Proveen Conectividad los Corredores de Hábitat? Algunos escépticos han cuestionado la evidencia empírica de que los corredores proveen conectividad al paisaje. Otros han sugerido los peligros de los corredores. Revisamos estudios publicados que abordaron empíricamente si los corredores fomentan o disminuyen la viabilidad de poblaciones de especies en parches de hábitat conectados por corredores. A la fecha no se ha llevado a cabo un diseño experimental randomizado y con réplicas para realizar inferencias sobre el valor de los corresdores en la conservación—y nosotros argüímos que no es necesario. En cambio, los estudios pueden emplear análisis observacional o experimental de parámetros de poblaciones de interés o movimientos individuales de animales. Dos de estas aproximaciones son muy prometedoras y pueden progresar, especialmente si las limitantes de los estudios previos son remediadas. Primero, los experimentos que usan parámetros demográficos como variables dependientes—aún si no son replicados—pueden demostrar efectos demográficos de corredores en paisajes particulares. Estos estudios deberán medir características demográficas antes y después del tratamiento, tanto en el área tratada (corredor creado o destruído) como en un área no tratada (parches de hábitat aislados unos de otros). Esta aproximación es superior a observar las condiciones demográficas en varios paisajes puesto que la presencia de un corredor tiende a estar correlacionada con otras variables, como lo es el tamaño del parche lo que puede confundir el análisis. Segundo, las observaciones de movimientos de animales que se desplazan normalmente en paisajes fragmentados puede demostrar el valor de los corredores en la conservación de manera mas convincente que los experimentos controlados sobre animales en movimiento. Este tipo de observaciones de campo están directamente relacionades con el tipo de animal (e.g., juveniles de la especie de interés dispersándose) y con el tipo de paisajes que están sujetos a las decisiones de preservación de corredores. Los estudios observacionales de movimientos de animales a futuro deberán tratar de detectar movimientos extra‐corredores y enfocarse a especies sensitivas a la fragmentación y para las cuales los corredores son factibles a ser propuestos. Menos de la mitad de los 32 estudios revisados provee datos persuasivos referentes a la utilidad de los corredores; otros estudios fueron inconclusos, mayormente debido a diseños defectuosos. Las evidencias de estudios bien diseñados sugieren que los corredores son herramientas valiosas de conservación. Aquellos que intentan destruir los últimos remanentes de conectividad natural deberían sustentarse demostrando que la destrucción de los corredores no afectará a poblaciones de interés.

Disturbance of the Seabed by Mobile Fishing Gear: A Comparison to Forest Clearcutting - Les Watling; Elliott A. Norse (Conservation Biology, 1998)
Bottom trawling and use of other mobile fishing gear have effects on the seabed that resemble forest clearcutting, a terrestrial disturbance recognized as a major threat to biological diversity and economic sustainability. Structures in marine benthic communities are generally much smaller than those in forests, but structural complexity is no less important to their biodiversity. Use of mobile fishing gear crushes, buries, and exposes marine animals and structures on and in the substratum, sharply reducing structural diversity. Its severity is roughly comparable to other natural and anthropogenic marine disturbances. It also alters biogeochemical cycles, perhaps even globally. Recovery after disturbance is often slow because recruitment is patchy and growth to maturity takes years, decades, or more for some structure‐forming species. Trawling and dredging are especially problematic where the return interval—the time from one dredging or trawling event to the next—is shorter than the time it takes for the ecosystem to recover; extensive areas can be trawled 100–700% per year or more. The effects of mobile fishing gear on biodiversity are most severe where natural disturbance is least prevalent, particularly on the outer continental shelf and slope, where storm‐wave damage is negligible and biological processes, including growth, tend to be slow. Recent advances in fishing technology (e.g., rockhopper gear, global positioning systems, fish finders) have all but eliminated what were de facto refuges from trawling. The frequency of trawling (in percentage of the continental shelf trawled per year) is orders of magnitude higher than other severe seabed disturbances, annually covering an area equivalent to perhaps half of the world’s continental shelf, or 150 times the land area that is clearcut yearly. Mobile fishing gear can have large and long‐lasting effects on benthic communities, including young stages of commercially important fishes, although some species benefit when structural complexity is reduced. These findings are crucial for implementation of “Essential Fish Habitat” provisions of the U.S. Magnuson‐Stevens Fishery Conservation and Management Act which aim to protect nursery and feeding habitat for commercial fishes. Using a precautionary approach to management, modifying fishing methods, and creating refuges free of mobile fishing gear are ways to reduce effects on biological diversity and commercial fish habitat. Perturbaciones del Lecho Marino por Artes de Pesca Móbiles: Una Comparación con la Tala Forestals Los arrastres de fondo y el uso de otras artes de pesca móviles tienen efectos en el lecho marino que se asemejan a la tala total de bosques, que es a su vez una pertubación terrestre reconocida como una de las mayores amenazas a la diversidad biológica y la sustentabilidad económica. Las estructuras en comunidades marinas bénticas son generalmente mucho más pequeñas que aquellas en los bosques, pero la complejidad estructural no es menos importante que la biodiversidad. El uso de artes de pesca móviles quiebra, sepulta y expone animales marinos y estructuras sobre y en el substrato, reduciendo marcadamente la diversidad estructural. Su severidad es burdamente comparable con otras perturbaciones marinas de orden natural o antropogénico. Tambien altera los ciclos biogeoquímicos, de hecho a nivel mundial. La recuperación después de una pertubación es frecuentemente lenta debido a que el reclutamiento es por parches y el crecimiento para alcanzar la madurez toma años, décadas o aún más para algunas especies que forman estructuras. Los arrastres de fondo y dragados son especialmente problemáticos donde el intervalo de retorno (tiempo entre un evento de dragado o arrastre y otro) es más corto que el tiempo que toma a un ecosistema recuperarse;árears extensas son arrastradas entre un 100 y 700% por año o mas. Los efectos de las artes de pesca móviles en la biodiversidad son más severos cuando las perturbaciones naturales son menos prevalentes, particularmente en las afueras de la plataforma continental y la pendiente, donde el daño del oleaje por tormentas es negligible y los procesos biológicos (incluyendo crecimiento) tienden a ser lentos. Recientes avances en tecnología pesquera (e.g., sistemas de posicionamiento global, detectores de peces) aparentemente tienen todo, pero eliminan lo que de facto fueran refugios contra arrastres. La frecuencia de los arrastres (en porcentaje de la plataforma continental arrastrada por año) es órdenes de magnitud mayor que otras perturbaciones severas al lecho marino, anualmente la cobertura de área es equivalente quizá a la mitad de la plataforma continental marina, o 150 veces el área de tierra que es talada anualmente. Las artes de pesca móviles pueden tener impactos grandes y de larga duración en las comunidades bentónicas, incluyendo estadios jóvenes de peces de importancia comercial, aunque algunas especies se benefician cuando la complejidad estructural es reducida. Estos descubrimientos son cruciales para la implementación de el “hábitat esencial para peces” del Acta de Conservación y Manejo de Pesquerias Magnuson‐Stevens de los Estados Unidos y que pretende establecer hábitats de reproducción y alimentación para peces comerciales. El uso de una aproximación precautoria de manejo, la modificación de métodos de pesca y la creación de refugios libres de artes de pesca móviles son formas para reducir los efectos en la diversidad biológica y el hábitat para peces comerciales.

The Relationship between Popularity and Body Size in Zoo Animals - Paul I. Ward; Nicole Mosberger; Claudia Kistler; Oliver Fischer (Conservation Biology, 1998)
Larger animals are more expensive to maintain in zoos than are smaller animals, and they breed at slower rates. Consequently, zoos could potentially contribute more to conservation efforts by concentrating on smaller‐bodied species, but they could lose patronage if the zoo’s public prefers to see larger species. Therefore, we examined the relationship between the popularity of zoo exhibits and the body sizes of the animals displayed. We measured popularity as the proportion of people passing an exhibit who looked at it for more than 10 seconds and compared popularity to the body size of the animals in the exhibit. We found that exhibits of larger animals were preferred by both adults and children. Children also showed a significant preference for larger groups of mammals. Although larger animals are more expensive to maintain, as estimated from adoption costs, a cost‐adjusted measure of popularity still yielded the conclusion that larger animals are more popular, especially with children. It thus may be premature to recommend that zoos concentrate on breeding smaller species to increase their potential contribution to conservation efforts because this would probably result in their exhibits being less popular. Relación entre la Popularidad y el Tamaño Corporal en Animales de Zoológico En los zoológicos, los animales grandes son más caros de mantener que los animales pequeños, además de que su tasa reproductiva es más baja. En consecuencia, los zoológicos contribuyen potencialmente más a los esfuerzos de conservación al concentrar esfuerzos en especies de cuerpos pequeños; sin embargo, los zoológicos podrían perder clientela si el público prefiere ver especies de cuerpo grande. Examinamos la relación entre la popularidad de las exhibiciones de zoológicos y el tamaño corporal de las especies exhibidas. Medimos la popularidad como la proporción de gente pasando por una exhibición y que la observó por más de 10 segundos y comparamos la popularidad con el tamaño del cuerpo de los animales exhibidos. Encontramos que las exhibiciones de animales grandes son preferidas tanto por adultos como por niños. Los niños mostraron además una preferencia significativa por los grupos de mamíferos grandes. Aunque los animales grandes son más caros de mantener en base a estimaciones de costo de adopción, una medida de ajuste en el costo en base a la popularidad mostró la conclusión de que los animales más grandes seguirían siendo más populares, especialmente entre los niños. Es aún prematuro recomendar que los zoológicos se concentren en la reproducción de especies pequeñas para incrementar su potencial contribución a los esfuerzos de conservación, puesto que esto podría resultar en una pérdida en la popularidad de sus exhibiciones.

Ecotourism’s Support of Biodiversity Conservation - Marnie P. Bookbinder; Eric Dinerstein; Arun Rijal; Hank Cauley; Arup Rajouria (Conservation Biology, 1998)
Ecotourism is often viewed as effective for promoting the conservation of endangered species and habitats in developing countries. By creating economic incentives for impoverished villagers or their communities, ecotourism is thought to encourage local guardianship of biological resources. To assess ecotourism’s effect on the income of villagers living near Royal Chitwan National Park, Nepal, one of the most heavily visited parks in Asia, we randomly surveyed 996 households in 7 of the 36 Village Development Committees adjacent to the park. Despite a 1994 visitation rate exceeding 60,000 tourists—most from industrial nations—the economic impact of ecotourism on household income was minimal and limited to villages closest to the main park’s entrance. Of the estimated 87,000 working‐age people living near the park, less than 1100 were employed directly by the ecotourism industry. Only 6% of the surveyed households earned income directly or indirectly from ecotourism; the average annual salary of these households from ecotourism was $600. Ecotourism in Royal Chitwan National Park, as it is currently structured, provides little employment potential, has a marginal effect on household income, and offers few benefits for local people. Thus, it is not a panacea for long‐term biodiversity conservation in this case. New policy changes, coupled with alternative approaches to the privately owned ecotourism industry, however, have the potential to redirect an appreciable amount of revenue to local development and strengthen local guardianship of endangered species and habitats. We urge that conservation biologists working in other areas ensure that well‐defined mechanisms for profit sharing with local communities are in place before advocating ecotourism development. Where ecotourism programs already exist without such profit‐sharing mechanisms, we urge conservationists to press for legislation that permits a percentage of profits to be spent on local community development. Soporte del Ecoturismo a la Conservación de la Biodiversidad El ecoturismo es frecuentemente visto como un medio efectivo para promover la conservación de especies y hábitats amenazados en países en desarrollo. Se cree que el ecoturismo promueve la custodia de los recursos biológicos locales al crear incentivos económicos para pobladores de bajos recursos en las comunidades aledañas. Para evaluar el efecto del ecoturismo en los ingresos de los pobladores que habitan cerca del Parque Nacional Royal Chitwan, en Nepal—uno de los parques más intensamente visitados en Asia—encuestamos al azar 996 familias en 7 de los 36 Comités de Desarrollo de Villas adyacentes al parque. A pesar de que la tasa de visitas en 1994 excedió los 60,000 turistas—la mayoría provenientes de países industrializados—el impacto económico del ecoturismo en los ingresos familiares fue mínimo y limitado a las villas más cercanas a la entrada del parque. De las 87,000 personas en edad de clase trabajadora que viven cerca del parque, menos de 1,100 fueron empleadas directamente por la industria del ecoturismo. Únicamente 6% de las familias encuestadas reciben ingresos directamente del ecoturismo; el salario promedio anual de estas familias fué de $600 USD. En la manera en que se encuentra estructurado actualmente el ecoturismo en el Parque Nacional Royal Chitwan, provee un potencial de empleo pequeño, tiene un efecto marginal en el ingreso familiar y ofrece pocos beneficios a las comunidades. Debido a esto, este caso no es una panacea para la conservación a largo plazo de la biodiversidad. Cambios en nuevas políticas acoplados a formas de abordar alternativas para la industria privada del ecoturismo tienen el potencial de re‐dirigir una cantidad apreciable de ingresos hacia el desarrollo local y fortalecer la custodia local de especies y hábitats amenazados. Urgimos a los biólogos de la conservación que trabajan en otras áreas que aseguren que los mecanismos de distribución de las ganancias con los pobladores sean bien definidos antes de que se proponga el desarrollo del ecoturismo. En los lugares donde ya existen programas de ecoturismo sin estos mecanismos de distribución de ganancias, urgimos a los conservacionistas para que presionen por una legislación que permita que un porcentaje de las ganancias sea canalizado hacia actividades de desarrollo en las comunidades locales.

Evidence from a Landscape Population Model of the Importance of Early Successional Habitat to the American Redstart - P. D. Hunt (Conservation Biology, 1998)

Edge‐Related Nest Predation in Clearcut and Groupcut Stands - David I. King; Richard M. DeGraaf; Curtice R. Griffin (Conservation Biology, 1998)
Edge‐related increases in nest predation rates have been reported in forest adjacent to clearcuts. Group selection is an uneven‐age silvicultural technique that may provide an alternative to clearcutting, but group selection creates more edge per unit area cut than does clearcutting. Thus, if edge‐related increases in nest predation exist in forest adjacent to groupcuts, group selection may potentially result in higher rates of edge‐related nest predation than does clearcutting. To test this, we deployed 80 artificial shrub nests baited with Zebra Finch ( Poephila guttata ) eggs in edge areas (0–5 m from edges) and interior areas (45–50 m from edges) adjacent to clearcuts and groupcuts. The probability of a nest being depredated was higher in edge areas than interior areas ( p = 0.02) and was independent of nest concealment, nest height, or whether the nest was adjacent to a clearcut or a groupcut ( p = 0.18). Thus, we conclude that forest edges created by groupcutting are associated with increased levels of nest predation in adjacent forest, that the magnitude of this edge effect is similar to increases in nest predation in forest adjacent to clearcuts, and therefore that the abandonment of clearcutting in favor of group selection cannot be justified on the basis of concerns about the welfare of mature, forest‐dwelling birds. Depredación de Nidos Relacionados con Bordes en Areas Taladas por Clareo y Tala en Grupo Se ha reportado un incremento en la tasa de depredación de nidos en relación con bordes adyacentes de áreas taladas por clareo. La selección de grupo es una técnica silvicultural con desbalance de edades que podría proveer una alternativa al clareo; sin embargo, la selección de grupos crea más borde por unidad de área cortada que el clareo. Por lo tanto, el incremento en la depredación de nidos con relación a bordes existe en bosques adyacentes a zonas de corte en grupos. La selección de grupos podría resultar potencialmente en tasas más altas de depredación de nidos relacionados con bordes que las zonas taladas por clareo. Para probar esto, distribuímos 80 nidos artificiales cebados con huevos de Pinzón cebra (Pheophila guttata) en áreas de borde (0–5 m del borde) e interiores (45–50 m del borde) adyacentes a áreas clareadas y taladas en grupo. La probabilidad de depredación de nidos fue mayor en áreas de borde que en los interiores ( p = 0.02) y fue independiente del ocultamiento de los nidos, altura del nido, o si el nido estaba adyacente a un clareo o a un corte de grupo. ( p = 0.18). Concluímos que los bordes en el bosque creados por corte en grupos están asociados con incrementos en los niveles de depredación de nidos en bosques adyacentes, que la magnitud del efecto de borde es similar a incrementos en depredación de nidos en bordes adyacentes a clareos y por lo tanto, que el abandono de corte por clareos en favor del corte por selección de grupos no puede ser justificado en base a las preocupaciones relacionadas con el bienestar de las aves que habitan bosques maduros.

Significance of Bottom‐Fishing Disturbance - Michel J. Kaiser (Conservation Biology, 1998)
Since the early 1970s there has been increasing interest in the ecological effects of bottom‐fishing activities on the benthic ecology of the seas of northern Europe. The majority of studies have examined the short‐term effects of disturbance on benthic fauna. Some areas, however, such as the southern North Sea, have been subjected to fishing disturbance for over 50 years, which complicates predictions of long‐term ecological change inferred from recent experimental studies. I highlight the importance of evaluating the ecological relevance of fishing disturbance versus natural perturbations, which varies among different habitats. Most experimental studies have shown that it is possible to detect short‐term changes in community structure in response to fishing disturbance. Evidence suggests that long‐term changes are probably restricted to long‐lived fragile species or communities found in environments that are infrequently disturbed by natural phenomena. Understanding the relative ecological importance of physical disturbance by fishing versus natural events would provide a basis for predicting the outcome of fishing activities in different marine habitats. I suggest approaches that may refine attempts to correlate fishing intensity and frequency with community change, such as the use of tracking devices fitted to trawlers and surveys of fauna, such as bivalves and echinoderms, that record disturbance events of the past in their shells or body structure. Importancia de la Perturbación de la Pesca de Fondo Desde principios de los años 70’s ha habido un creciente interés en los efectos ecológicos de las actividades de pesca de fondo en la ecología béntica de los mares del Norte de Europa. La mayoría de estos estudios han examinado los efectos de las perturbaciones sobre la fauna bentónica a corto plazo. Sin embargo, en algunas áreas como la zona sur del Mar del Norte, han sido sujetas a perturbaciones por pesca por mas de 50 años, lo cual complica las predicciones de cambio ecológico a largo plazo establecidas a partir de estudios experimentales recientes. Remarco la importancia de la evaluación de la relevancia ecológica de la perturbación pesquera contra perturbaciones naturales que varían entre diferentes hábitats. La mayoría de los estudios experimentales han mostrado que es posible detectar cambios a corto plazo en la estructura comunitaria en respuesta a perturbaciones pesqueras. Las evidencias sugieren que los cambios a largo plazo están probablemente restringidos a especies frágiles de vida larga o a comunidades encontradas en ambientes que no son perturbados frecuentemente por fenómenos naturales. El entendimiento de la importancia ecológica relativa de las perturbaciones físicas debidas a la pesca comparada con eventos naturales podría proveer una base para la predicción de los resultados de la pesca en diferentes hábitats marinos. Sugiero aproximaciones que podrían refinar esfuerzos para correlacionar la intensidad pesquera y su frecuencia con cambios en las comunidades como lo son el uso de artefactos adaptados a los sistemas de arrastre y muestreos de fauna—como los bivalvos y equinodermos—que registran eventos pasados de perturbación en sus conchas o en la estructura de sus cuerpos.

Do Habitat Corridors Provide Connectivity? - Paul Beier; Reed F. Noss (Conservation Biology, 1998)

Conservation Biology in Your Own Front Yard - Christopher Uhl (Conservation Biology, 1998)

Special Section: Effects of Mobile Fishing Gear on Marine Benthos - Les Watling; Elliott A. Norse (Conservation Biology, 1998)

Inference Methods for Spatial Variation in Species Richness and Community Composition When Not All Species Are Detected - James D. Nichols; Thierry Boulinier; James E. Hines; Kenneth H. Pollock; John R. Sauer (Conservation Biology, 1998)

Distribution of Alkaloid‐Rich Plant Species in Shortgrass Steppe Vegetation - Donald L. Hazlett; Neil W. Sawyer (Conservation Biology, 1998)
We investigated the distribution of alkaloid‐rich plant species in shortgrass steppe vegetation. The intent was to identify and to determine if alkaloid‐rich species were more prevalent in certain habitats or life forms and to determine if ethnomedicinal accounts were an indicator of alkaloid‐rich taxa. Alkaloid screening tests were performed on plant tissues from 77% of 275 plant species that occurred at the Central Plains Experimental Range. There were alkaloid‐positive results for 10% of all species tested. When alkaloid‐rich plant taxa were categorized by habitat, none of six habitats had a significantly greater percentage of alkaloid‐rich species. Nevertheless, about three‐fourths of all plant taxa and of all alkaloid‐rich taxa occurred in “water‐enriched” habitats, which composed less than 20% of the study area. A higher percentage of alkaloid‐positive species was found among forbs, especially biennial forbs, than among graminoids. There were ethnomedicinal reports for 23% of all study species. The percentage of alkaloid‐rich species was similar for species with and without ethnomedicinal uses. A natural product database indicated that 46% of native plant species in the study area had been screened and had tested positive for at least one type of biological activity. The chemical structures of plant chemicals had been identified for only 12% of all species, however. Technologies are rapidly developing to screen for and utilize plant chemical resources. Therefore, conservation biologists should be aware of plant species and habitats that have unique or potentially useful plant chemicals. Land managers can use baseline plant chemical data to begin an evaluation of current policies in regard to the protection of this natural resource. Distribución de Especies de Plantas Ricas en Alcaloides en Vegetación de Estepas de Pastos Cortos Investigamos la distribución de los quimicos alcaloides en plantas de la vegetación de la pradera. El propósito fue identificar y determinar si las especies de plantas con alcaloides fueron más predominantes en ciertos hábitats o formas de vida y determinar si la información etnobotànica fue un buen indicador para especies de plantas que tienen alcaloides. Se hicieron ensayos químicos para alcaloides usando los tejidos de 77% de las 275 especies de plantas que ocurrieron en el área del estudio. Resultados positivos ocurrieron en 10% de las especies ensayadas. Ninguno de los seis hábitats tuvieron significativamente más especies con ensayos positivos para alcaloides. Casi tres‐cuartos de todas las especies en el área del estudio ocurrieron en los hábitats que recibieron, debido a su posición topográfica y suelos, agua adicional. Estos hábitats constituyeron menos del 20% del área del estudio. Había un porcentaje mayor de especies con resultados positivos con alcaloides entre plantas no gramíneas, especialmente entre bianuales, que entre plantas gramíneas. Reportes etnobotánicos fureon encontrados en 23% de las especies estudiadas. No hubo un porcentaje mayor de ensayos positivos para alcaloides entre especies de plantas con reportes etnobotánicos que entre especies que no tenían reportes etnobotánicos. Estudios químicos reportados en la literatura indicaran que 46% de las especies de plantas en el lugar de este estudio tenían por lo menos un reporte clínico de actividad biológica. Sin embargo, investigaciones para determinar la estructura química de plantas han sido realizados solamente en 12% de las especies. Tecnologías nuevas están desarrollándose rápidamente para ensayar y utilizar los recursos químicos de las plantas. Por lo tanto, los biólogos en favor de la conservación deben darse cuenta de cuáles son las especies de plantas y los hábitats donde se encuentran químicos útiles. Entonces será posible evaluar si las decisiones administrativas actuales son adequadas para la protección de este recurso natural.

Edge Effects on an Epiphytic Lichen in Fragmented Forests - Per-Anders Esseen; Karl-Erik Renhorn (Conservation Biology, 1998)

Conservation of Pacific Salmon: Response to Wainwright and Waples - Kenneth P. Currens; Fred W. Allendorf; David Bayles; Daniel L. Bottom; Christopher A. Frissell; David Hankin; James A. Lichatowich; Patrick C. Trotter; Thomas A. Williams (Conservation Biology, 1998)

The Green University - Stephen C. Trombulak; Susan Bratton; Mark H. Waugh; David Pimentel; James M. Peek (Conservation Biology, 1998)

Concerns about Rehabilitation of Oiled Wildlife* - J. A. Estes (Conservation Biology, 1998)

Tameness of Insular Lizards and Loss of Biological Diversity - Miguel Delibes; M. Carmen Blázquez (Conservation Biology, 1998)

Number of Censuses Required for Demographic Estimation of Effective Population Size - John A. Vucetich; Thomas A. Waite (Conservation Biology, 1998)
Adequate population viability assessment may require estimation of effective population size ( N e ). But failure to take into account the effect of temporal fluctuation in population size (FPS) on N e may routinely lead to unrealistically optimistic viability assessments. We thus evaluate a technique that accounts for the effect of FPS on N e . Using time series of annual counts of 48 free‐ranging animal populations, we show that N e is dependent on timescale: as more census records are incorporated, estimates of FPS tend to increase, and thus estimates of N e tend to decrease. Estimates based on, say, 10 annual counts tend to grossly underestimate the influence of FPS on estimates of long‐term N e , often by more than 100%. Moreover, a newly derived expression for the confidence intervals of N e / N (in which N is population size) reveals that estimates of N e based on only a few annual counts are quite unreliable. Our work thus emphasizes the need for long‐term population monitoring and provides a framework for interpreting N e estimates calculated from limited census data. Número de Censos Requeridos para una Estimación Demográfica Efectiva de Tamaño Poblacional Evaluaciones adecuadas de viabilidad poblacional pueden requerir estimaciones de tamaño poblacional efectivo ( N e ). Sin embargo, omisiones en la consideración del efecto de la fluctuación temporal del tamaño poblacional (FPS) en N e pueden conducir rutinariamente a estimaciones de viabilidad irrealmente optimistas. Es por ello que evaluamos una técnica que toma en consideración el efecto de FPS en N e . Utilizamos series de tiempo de conteos anuales de 48 poblaciones de animales de rango libre, mostramos que N e es dependiente de la escala temporal: mientras más registros de censos son incorporados, las estimaciones de FPS tienden a incrementar y por lo tanto las estimaciones de N e tienden a disminuir. Estimaciones basadas, en por ejemplo, 10 conteos anuales tienden a subestimar la influencia de FPS en las estimaciones de largo plazo de N e (frecuentemente por más de un 100%). Mas aún, una nueva expresión derivada para intervalos de confianza de N e / N (en la cual N es el tamaño poblacional) revela que las estimaciones de N e basadas en solo unos cuantos conteos anuales son poco confiables. Nuestro trabajo hace énfasis en la necesidad de monitoreos poblacionales a largo plazo y provee un marco de trabajo para interpretar estimaciones de N e calculadas a partir de datos de censos limitados.

An Evaluation and Modification of World Conservation Union Red List Criteria for Classification of Extinction Risk in Vascular Plants - David A. Keith (Conservation Biology, 1998)
The World Conservation Union (IUCN) Red List criteria endorsed in 1994 consist of a set of decision rules based on quantitative thresholds of population size, distributional range, rates of decline, and extinction risk. I evaluated these criteria using data on 68 vascular plant taxa from southeastern Australia and found that deficiencies could be overcome with modifications that did not substantially alter the structure of the IUCN rule set. These modifications included smaller distributional thresholds appropriate to sessile organisms, inclusion of life‐history and land‐based attributes, an amendment to account for skewed metapopulation structure, and inclusion of a rule addressing number of populations and qualitatively defined classes of threatening processes. I reviewed the strengths and weaknesses of decision rules for risk classification such as those endorsed by the World Conservation Union compared with intuitively based qualitative schemes in traditional use. I concluded that explicit schemes foster greater accuracy and precision in risk classification, are more defensible in the face of challenges, and define an agenda for data collection that is essential for the ongoing assessment and management of threatened species. Evaluación y Modificación de los Criterios de Clasifícación de Riesgo de Extinción en Plantas Vasculares de la Lista Roja del IUCN Los criterios de la lista roja del IUCN establecidos en 1994 constituyen un juego de reglas de decisión basadas en límites cuantitativos de tamaño poblacional, rango de distribución, tasas de declive y riesgo de extinción. Evaluamos estos criterios usando datos de 68 taxa de plantas vasculares del sureste de Australia y encontramos que ciertas deficiencias pueden ser resueltas con modificaciones que no alteran sustancialmente la estructura del juego de reglas del IUCN. Estas modificaciones incluyen límites de distribución más pequeños apropiados para organismos sésiles, inclusión de atributos de la historia de vida y en base al terreno, una enmienda que considere estructucturas metapoblacionales sesgadas y la inclusión de una regla que considere el número de poblaciones y clases cuantitativamente definidas de los procesos de amenaza. Revisamos la fortaleza y debilidad de las reglas de decisión para clasificación de riesgos como lo son las reglas del IUCN comparadas con esquemas cualitativos con bases intuitivas de uso tradicional. Concluimos que los esquemas explícitos amplían la precisión y exactitud de las clasifcaciones de riesgo, son más defensivas en presencia de desafios y definen una agenda para la colección de datos que es esencial para la evaluación en curso y manejo de especies amenazadas.

Comparison of Isozymes and Quantitative Traits for Evaluating Patterns of Genetic Variation in Purple Needlegrass ( Nassella pulchra ) - Eric E. Knapp; Kevin J. Rice (Conservation Biology, 1998)
Decimation of the California (U.S.A.) prairie has increased interest in the conservation and ecological restoration of grasslands composed of native perennial species. Widespread plantings are being attempted, and the potential for contaminating existing remnant populations with maladapted germplasm has led to concerns about the use of nonlocal seed sources. We evaluated regional patterns of isozyme and quantitative trait variation in the native perennial grass Nassella pulchra for the purpose of developing recommendations about the spatial scales over which seed can be translocated. Seed was collected from 10 remnant native populations. Progeny from all 10 populations were scored for isozyme variation with 11 stains, and progeny from 8 populations were planted in a common garden to evaluate variation for 11 quantitative (polygenic) traits. The correspondence between isozyme and quantitative trait variation and the relationships of both types of variation to geographic distance and climate were explored by Mantel test regressions. Populations were strongly differentiated for both isozymes and quantitative traits, but cluster analysis based on each type of data did not result in the same population groupings. This lack of congruence was further demonstrated by the nonsignificance of the regression of Hedrick’s distances for isozymes on Mahalanobis distances for quantitative traits. Quantitative trait variation was strongly associated with climatic variables, whereas isozyme variation was not. This suggests that the relative importance of genetic drift and selection in shaping patterns of genetic differentiation may depend upon the type of trait evaluated. Quantitative traits are potentially better indicators of adaptation to regional and local environmental variation, and thus the usefulness of isozymes for making recommendations about the spatial scales over which seed of N. pulchra can be translocated may be limited. Unfortunately, obtaining data on patterns of quantitative trait variation is often time‐ and labor‐intensive. The close association of quantitative trait variation with regional climatic variables indicates that an index based on readily obtainable climatic information might aid restorationists in making rapid decisions about appropriate spatial scales for translocating native grasses. Compariciones de Isozimas y Rasgos Cuantitativos para Evaluar Patrones de Variación Genética en el Pasto‐Aguja Morado ( Nasella pulchra) La disminución de la pradera de California (USA) ha incrementado el interés en la conservación y restauración ecológica de pastizales compuestos por especies perennes nativas. La dispersión amplia de siembras se ha intentado y el potencial de contaminación de poblaciones remanentes con germoplasmas mal adaptados ha generado preocupaciones sobre el uso de fuentes de semilla no locales. Evaluamos patrones regionales de variación de isozimas y variación cuantitativa de rasgos en el pasto perenne nativo Nasella pulchra con el propósito de desarrollar recomendaciones sobre las escalas espaciales en las cuales las semillas pueden ser movidas. Las semillas fueron colectadas a partir de 10 poblaciones remanentes nativas. Las progenies de las 10 poblaciones fueron evaluados para variación de isozima usando 11 colorantes y las progenies de 8 poblaciones fueron plantadas en un jardín común para evaluar la variación de 11 rasgos (poligenéticos) cuantitativos. La correspondencia entre variaciones de isozimas y de rasgos cuantitativos y las relaciones de ambos tipos de variación con distancia geográfica y clima fue explorada usando pruebas de regresión de Mantel. Sin embargo, los análisis de conjunto basados en cada tipo de datos no dió como resultado las mismas agrupaciones de poblaciones. Esta carencia de congruencia fue demonstrada más adelante por la no significancia de la regresión de distancias de Hendrick para isozimas en distancias Mahalanobis para rasgos cuantitativos. La variación en rasgos cuantitativos estuvo fuertemente asociada con las variables climáticas, mientras que la variación de isozimas no lo estuvo. Esto sugiere que la importancia relativa de la deriva génica y de la selección en patrones de forma de diferenciación genética pueden depender del tipo de rasgo evaluado. Los rasgos cuantitativos son potencialmente mejores indicadores de adaptación a la variación ambiental local y regional, por lo tanto la utildad de isozimas para hacer recomendaciones sobre escalas espaciales en las cuales las semillas de N. pulchra pueden ser movidas puede verse limitada. Desafortunadamente, la obtención de datos de patrones de variación de rasgos cuantitativos require frecuentemente de tiempo y esfuerzo intensivos. La asociación cercana de variación de rasgos cuantitativos con variables climáticas regionales indica que un indice basado en información climática accesible podría ayudar a los restauradores a tomar decisiones rápidas sobre escalas espaciales apropiadas para mover pastos nativos.

Social Construction, Political Power, and the Allocation of Benefits to Endangered Species - Brian Czech; Paul R. Krausman; Rena Borkhataria (Conservation Biology, 1998)
Social construction is the virtue ascribed to a subject by the general public; along with political power, it influences the allocation of public policy benefits. Nonhuman species are socially constructed by humans, and political power is held in trust for them by human interest groups. Our goal was to determine if the allocation of benefits to endangered species is consistent with social construction and political power. We assessed the social construction of broad types of species using survey data collected from a national sample of 643 respondents. We found that plants, birds, mammals, and fish have a distinctly more positive social construction than reptiles, amphibians, invertebrates, and microorganisms. Respondents also indicated, however, that all nonhuman species should be conserved and that ecological importance and rarity are the most important factors to consider in prioritizing species for conservation. We gauged the political power affiliated with types of species by the number of nongovernmental organizations representing them. Birds have a substantial advantage over all other types. We employed a political science model that identifies policy subjects based on social construction and political power and identified birds, mammals, and fish as “advantaged” subjects, plants as “dependents,” and reptiles, amphibians, invertebrates, and microorganisms as “deviants.” Numerous exceptions, especially among mammals, are best described as “contenders.” Allocation of the benefits of the U.S. Endangered Species Act is consistent with predictions of the model. A myriad of values converge to favor birds, mammals, fish, and plants in the policy arena. The most promising opportunities for species conservation in the political arena, however, may be with plants and amphibians, for which the ratio of social construction to benefit allocation is highest. Opinión Pública, Poder Politico, y Ubiación de Beneficios para Especies Amenazadas La opinión pública y el poder político influencian la distribución de beneficios hacia los sujetos humano de la política. La opinión pública sobre especies no humanas está también determinada por el ser humanos, y el poder político asociado a estas especies se ejerce a través de grupos interesados en ellas. Nuestro objetivo fue determinar si la distribución de beneficios dirigidos a especies en peligro de extinción es consecuente con la opinión pública y el poder político. Realizamos una evaluación de la opinión pública sobre grupos amplios de tipos de especies usando datos de encuestas nacionales. Encontramos que las plantas, las aves, los mamíferos, y los peces tienen una opinión pública claramente más positiva que los reptiles, los anfibios, los invertebrados y los microorganismos. Sin embargo, las personas que respondieron la encuesta indicaron que es esencial conservar a todas las especies animales no humanas, y que la importancia ecológica y la rareza son los factores más importantes a considerar al priorizar las especies para su conservación. Medimos el poder político asociado a tipos de especies por medio del número de organizaciones no gubernamentales que los representan. Las aves tienen una importancia substancial en relación a todos los otros tipos. Usamos un modelo desarrollado para ciencias políticas que identifica los sujetos de la política en base a la opinión pública y el poder político, e identificamos a las aves, los mamíferos, y los peces como sujetos “con ventaja,” las plantas como sujetos “dependientes,” y los reptiles, los anfibios, los invertebrados y los microorganismos como sujetos “desviados de lo común.” Numerosas excepciones, especialmente entre mamíferos, son descritas como “contendientes.” Las discrepancias entre la valuación pública y la distribución de recursos para esfuerzos de recuperación son consistentes con las predicciones del modelo. Se concluye que hay un gran número de valores que convergen a favor de las aves, los mamíferos, los peces, y las plantas en el terreno político. Sin embargo, las oportunidades más prometedoras para la conservación de especies en el terreno político pueden estar en las plantas y los anfibios, para los que el cociente entre la opinión pública y la distribución de beneficios es la más alta.

Assessment of Threat and Conservation Priorities under Realistic Levels of Uncertainty and Reliability - Charles R. Todd; Mark A. Burgman (Conservation Biology, 1998)
Most current methods available for assessing the conservation status of a species do not take into account the underlying uncertainty inherent in the data. A point estimate approach is generally adopted to interpret the data used in these assessments. For species that are not well known, the paucity of quality data produces an unreliable estimate of the species’ status. The assessment of threat, based upon a range of values reflecting the uncertainty in parameter estimates, can be undertaken within the framework of fuzzy sets and used to broaden the evaluation of a species. When the parameter estimates of two biological variables are combined, the use of fuzzy sets in conjunction with a point scoring convention generates a range of plausible outcomes, rather than a single outcome that would result from the point estimate approach. Different types of uncertainty, including probabilistic uncertainty and reasonable bounds for expert judgment, can be interpreted and used to provide a measure of reliability of the outcomes. The measure of reliability ranks each outcome and provides a statement about which outcome best represents the level of threat faced by a species. The incorporation of fuzzy sets into a current convention shows that consideration of uncertainty may change the assessment of a species and accordingly the conservation priorities. Evalación de la Amenaza y las Prioridades de Conservación Bajo Niveles Realistas de Incertidumbre y Confiabilidad Los métodos más comúnmente utilizados para determinar el estado de una especie para su conservación no consideran la incertidumbre existente en los datos disponibles para dicho análisis. Estos métodos generalmente utilizan estimados puntuales en la interpretación de los datos y por esto resultan inadecuados cuando son aplicados a especies poco conocidas dado que la escasez de datos confiables puede llevar a conclusiones incorrectas sobre el estado de la especie. La evaluación del riesgo de una especie basada en el uso de intervalos que reflejan la incertidumbre de los parámetros estimados, puede ser llevada a cabo usando “intervalos difusos” (fuzzy sets). Cuando los parámetros estimados de dos o más variables biológicas son combinanados, el uso de intervalos difusos en combinación con métodos basados en estimados puntuales, aumenta el espectro de resultados posibles en la evaluación del estado de la especie. Distintos tipos de incertidumbre, incluyendo la incertidumbre probabilística y las razonables dudas asociadas a las estimaciones de los expertos, pueden ser interpretadas y utilizadas para evaluar la validez de los resultados. Las medidas de confianza en los datos otorgan un orden a cada resultado y además proveen un criterio para decidir cuál de los resultados representa mejor el nivel de riesgo de la especies en consideración. La incorporación de los intervalos difusos en los métodos convencionales demuestra que la inclusión de incertidumbre en los datos puede cambiar las interpretaciones sobre el estado de las especies y de esta manera, los criterios y prioridades para su conservación.

Historical and Contemporary Maternal Population Structuring in the Endangered Hastings River Mouse ( Pseudomys oralis ) - Dean R. Jerry; Tanya A. Dow; Martin S. Elphinstone; Peter R. Baverstock (Conservation Biology, 1998)
The Hastings River mouse ( Pseudomys oralis ) is a small, endangered Australian conilurine rodent. Only about 200 specimens of this rodent have ever been caught, and little is known about its biology. At present, populations of this species appear to be severely fragmented. We used temperature‐gradient gel electrophoresis and DNA sequencing to investigate maternal population structuring in this species and to determine if the pattern of fragmentation is the consequence of anthropogenic influences. Based on a 345 bp section of the mitochondrial control region, all sample localities were found to be genetically distinct, with only 1 haplotype out of 11 found present in more than one sample locale. Phylogenetic reconstructions from sequence data clustered haplotypes into two distinct clades, demonstrating that contemporary population structure in the Hastings River mouse has a historical component. The discovery that populations of the Hastings River mouse are not only currently genetically isolated but have been separated for long periods of evolutionary time has clear management ramifications for the conservation of this species. In particular, each population should now be treated as demographically independent and administered as a separate management unit. Estructura Histórica y Contemporánea de la Población Materna de el Ratón del Rio Hastings ( Pseudomys oralis ) en Peligro de Extinción. El ratón del río Hastings ( Pseudomys oralis ) es un roedor australiano pequeño en peligro de extinción. Unicamente 200 especímenes de este roedor han sido capturados y se conoce muy poco de su biologia. Actualmente, las poblaciones de esta especie aparentan estar severamente fragmentadas. Utilizamos gel electroforésis de gradiente de temperatura y secuenciado de ADN para investigar la estructura poblacional materna en la especie y para examinar si los patrones de fragmentación son consecuencia de influencias antropogénicas. Basados en secciones de 345 bp de la region de control mitocondrial, todas las muestras fueron encontradas genéticamente distintas, con un haplotipo de once encontrados presente en mas de una muestra. Reconstrucciones filogenéticas de datos de secuencias agrupó haplotipos en dos grupos distintivos, demostrando que poblaciones contemporáneas del raton del río Hastings tiene un componente histórico. El descubrimiento de que poblaciones del ratón del río Hastings no estan solo aisladas genéticamente en la actualidad, sino que han estado separadas por largos períodos de tiempo evolucionario tiene ramificaciones claras de manejo para la conservación de esta especie. En particular, cada población deberá ser tratada ahora como demográficamente independiente y administrada como una unidad de manejo separada.

Demography and Population Trend of Grizzly Bears in the Swan Mountains, Montana - Richard D. Mace; John S. Waller (Conservation Biology, 1998)
From 1987 to 1996 we used capture and telemetry methods to study the demography, movements, and population trend of grizzly bears ( Ursus arctos horribilis ) in wilderness and nonwilderness portions of the Swan Mountains of Montana. Most data were collected in the nonwilderness portion, which included public multiple‐use lands and rural areas on and near private lands. Population density in nonwilderness averaged 1.6 bears/100 km 2 . The annual total mortality rate (13.4%) was higher than that found in expanding brown bear ( Ursus arctos ) populations. A tenuous finite rate of increase (λ) of 0.977 (95% CI = 0.875–1.046) was related to high female mortality. Annual mortality rates for bears utilizing the rural and wilderness zones was 21 and 15 times higher, respectively, than for bears using only multiple‐use lands. Our mortality, movement, and occupancy data suggest that the multiple‐use zone is a population source area, and that wilderness and rural zones are sink areas. Mortalities in the wilderness zone were from mistaken identification during the black bear ( Ursus americanus ) hunting season and human defense of life. In the rural zone, mortalities were from malicious killing and the management removal of habituated or food‐conditioned bears. We recommend that wildlife managers develop a conservation strategy to promote bear population stability or growth by improving female survival while minimizing bear conflicts on private lands. This would be accomplished by protecting core areas on public lands of superior habitat through access management, conducting a mandatory bear identification course for black bear hunters, and reducing anthropogenic foods on private lands. We also recommend a continuing population and habitat monitoring program. Demografia y Tendencias del Oso Grizzly en las Montañas Swan, Montana De 1987 a 1996 utilizamos métodos de captura y telemetría para estudiar la demografa, movimientos y tendencias de los osos grizzly ( Ursus arctos horribilis ) en porciones silvestres y no‐silvestres de las monatñas Swan, Montana. La mayoría de los datos fueron colectados en la porción no‐silvestre, la cual incluye tierras públicas de usos múltiples y áreas rurales en o cerca de propiedades privadas. La densidad poblacional en áreas no‐silvestres promedió 1.6 osos/100 km 2 . La tasa de mortalidad anual (13.4%) fue más alta que la encontrada en poblaciones de osos pardos ( Ursus arctos ) en expansión. Una tenue tasa finita de crecimiento (λ) de 0.977 (95% CI = 0.875–1.046) estuvo relacionada con la alta mortalidad de hembras. Las tasas de mortalidad de osos que utilizan áreas rurales y zonas silvestres fue 21 y 15 veces más alta respectivamente, que la de osos que usan sólo tierras de usos multiples. Nuestros datos de mortalidad, movimiento y ocupación sugieren que la zona de usos múltiples es un área fuenta, mientras que las áreas silvestre y rural son áreas sumidero. Mortalidades en las zonas silvetres fueron ocasionadas por identificación errónea durante la temporada de caza del oso negro ( Ursus americanus ) y en defensa de vidas humanas. En la zona rural las mortalidades fueron por asesinatos maliciosos y remoción por manejo de osos habituados o condicionados a comida. Recommendamos a los manejadores de vida silvestre desarrollar una estrategia de conservación para promover la estabilidad o crecimiento de las poblaciones de osos improvisando la supervivencia de hembras al mismo tiempo que se minimizan los conflictos por osos en tierras privadas. Esto podría ser llevado a cabo protegiendo áreas medulares en las tierras públicas de hábitat superior mediante el manejo del acceso, conduciendo un curso de identificación para cazadores de osos negros y reduciendo alimentos de origen antropogénico en tierras privadas. También se recomienda un programa de monitoreo de la población y el hábitat.

Biological Delineation of Terrestrial Buffer Zones for Pond‐Breeding Salamanders - Raymond D. Semlitsch (Conservation Biology, 1998)
Many semi‐aquatic organisms, such as salamanders, depend on both aquatic and terrestrial habitats to complete their life cycle and maintain viable populations. But current U.S. federal and state regulations protect only the wetland itself or arbitrarily defined portions of terrestrial habitat, if any. Part of the reason terrestrial habitats adjacent to wetlands are not protected is the lack of a clear understanding of the distances from shorelines that are biologically relevant to wetland fauna. Such information is critical for delineation of terrestrial “buffer zones” for wetlands, and thus for the conservation of semi‐aquatic organisms. I summarized data from the literature on terrestrial habitat use by one group of pond‐breeding salamanders, especially distances individuals traveled away from ponds. The results provide a basis for setting terrestrial buffer zones determined from actual habitat use by adult and juvenile salamanders. The mean distance salamanders were found from the edge of aquatic habitats was 125.3 m for adults of six species and 69.6 m for juveniles of two of these species. Assuming that the mean distance encompasses 50% of the population, a buffer zone encompassing 95% of the population would extend 164.3 m (534 ft) from a wetland’s edge into the terrestrial habitat. Data from other amphibians suggest that this buffer zone is applicable to a range of species, but caution should be taken for taxa suspected to be more vagile. Wetland managers and policymakers must recognize the special needs of semi‐aquatic organisms during their entire life cycle, not just during the breeding season. To maintain viable populations and communities of salamanders, attention must be directed to the terrestrial areas peripheral to all wetlands. Data on habitat use from salamanders and other semi‐aquatic species make it increasingly apparent that maintaining the connection between wetlands and terrestrial habitats will be necessary to preserve the remaining biodiversity of our vanishing wetlands. Delineación Biológica de Zonas Terrestres de Amortiguamiento para Salamandras con Reproducción en Charcas Muchos organismos semi‐acuáticos, como son las salamandras, dependen tanto de hábitats acuáticos como terrestres para completar su ciclo de vida y mantener poblaciones viables. Sin embargo, las actuales regulaciones federales y estatales en los Estados Unidos protegen unicamente a los humedales o a porciones de hábitat terrestres (de ser posible). Parte de las razones por las cuales los hábitates terrestres adyacentes a humedales no son protegidos se debe a la carencia de un claro entendimiento de las distancias biológicamente relevantes partiendo de los bordes y que son utilizados por la fuana del humedal. Esta información es crítica para delinear zonas terrestres de “amortiguamiento” para humedales, y en consecuencia para la conservación de organismos semi‐acuáticos. Resumo datos de la literatura sobre el uso de hábitat terrestre por un grupo de salamandras con reproducción en charcas, especialmente de distancias individuales viajadas hacia afuera de las charcas. Los resultados proveen las bases para establecer zonas terrestres de amortiguamiento determinadas a partir del uso actual del hábitat por salamandras adultas y juveniles. La distancia media a partir del borde de los hábitats acuáticos en la cual las salamandras fueron encontradas fue de 125.3 m para adultos de seis especies y de 69.6 m para juveniles de dos de estas especies. Asumiendo que la distancia media abarca un 50% de la población, una zona de amortiguamiento que abarque 95% de la población podría extenderse hasta los 164.3 m (534 pies) partiendo del borde del humedal hacia el hábitat terrestre. Datos de ostros anfibios sugieren que esta zona de amortiguamiento es aplicable para un rango de especies, pero se deben tomar precauciones para taxes de los que se sospecha se desplazan mas. Manejadores de humedales y estructuradores de políticas deben reconocer las necesidades especiales de organismos semi‐acuáticos a lo largo de su ciclo de vida completo, no solo durante la temporada de reproducción. Se debe dirijir especial atención a las áreas terrestres periféricas a todos los humedales para mantener poblaciones viables y comunidades de salamandras. Datos de uso del hábitat por salamandras y otras especies semi‐acuáticas hacen mas aparente la necesidad de mantener la conección entre humedales y hábitats terrestres para conservar la biodiversidad que aún queda en nuestros humedales en desaparición.

Population Viability of Rorippa columbiae : Multiple Models and Spatial Trend Data - Elizabeth E. Crone; Janet L. Gehring (Conservation Biology, 1998)
In managing rare species for conservation, we often need to make decisions based on existing, scanty data sets. Our ability to use such data effectively may be critical to our success in managing individual populations. We used viability analysis to examine the population dynamics of a threatened plant species, Rorippa columbiae , on Pierce Island in Washington (U.S.A.). Although the island was protected in part because of the presence of R. columbiae , monitoring suggested that plant density declined on the island after the preserve was established. To understand the implications of this decline, we generated a number of hypotheses about factors that might be important in controlling population dynamics in R. columbiae : density dependence, size dependence, spatial environmental heterogeneity among sites, and dispersal and colonization of new sites. Using statistical and biological criteria, we were able to rule out the hypotheses of size‐dependent population growth rates and dispersal among sites, but the importance of spatial heterogeneity and density dependence was ambiguous. Models with and without spatial heterogeneity make radically different predictions about the future of R. columbiae on Pierce Island: with spatial heterogeneity we expect persistence, albeit at a limited number of sites, whereas in a spatially uniform environment we expect extinction in the near future. This emphasizes the uncertain future of this population but tells us that ecological differences among sites and correlates of population vigor are important data to collect in future studies. Our analysis also points to the importance of maintaining multiple working hypotheses about controls of population growth when interpreting population trends from limited data. Viabilidad Poblacional de Rorippa columbiae : Modelos Múltiples y Datos de Tendencia Espacial Al manejar especies escasas de cara a su conservación, a menudo se necesitan tomar decisiones basadas en una información existente, que con frecuencia es escasa. La habilidad en el uso de estos datos de manera efectiva, puede determinar de forma crítica nuestro éxito en el manejo de poblaciones. En este estudio, se utilizan análisis de viabilidad para examinar la dinámica poblacional de una especie vegetal amenazada, Rorippa columbiae , en la isla Pierce, Washington. Aunque uno de los motivos para proteger la isla fue la presencia de R. columbiae, el seguimento realizado sugiere que su densidad dismiuyó tras la protección de este espacio. Para entender las implicaciones de dicha disminución, se generaron una serie de hipótesis sobre los factores que pueden ser importantes para controlar la dinámica poblacional de R. columbiae : dependencia de la densidad, dependencia del tamaño, heterogeneidad espacial entre localidades y dispersión/colonización. Mediante el uso de criterios estadísticos y biológicos, nos fue posible descartar las hipótesis de crecimiento poblacional dependiente del tamaño y de dispersión entre áreas. Sin embargo, la importancia de la heterogeneidad espacial y de la dependencia de la densidad es ambigua. Incluir o no la heterogeneidad espacial en los modelos, da como resultado predicciones radicalmente distintas sobre el futuro de R. columbiae en la isla de Pierce: al incluir la heterogeneidad espacial se predice persistencia, aunque en un número limitado de localidades, mientras que en un medio espacialmente uniforme, se predice la extinción en un futuro próximo. Esto aumenta nuestra incertidumbre sobre el futuro de la población, pero destaca que las diferencias ecológicas entre localidades y las correlaciones de salud poblacional son datos importantes para recolectar en estudios futuros. Nuestro análisis también apunta la relavancia de manejar múltiples hipótesis de trabajo para predecir las dinámicas poblacionales a la hora de interpretar las tendencias poblacionales basadas en datos limitados.

Relationships between Population and Habitat Characteristics and Reproduction of the Rare Gentiana pneumonanthe L. - J. Gerard B. Oostermeijer; Sheila H. Luijten; Zdenka V. Křenová; Hans C. M. Den Nijs (Conservation Biology, 1998)
We investigated the relationships among a number of population and site characteristics and the ovule and seed production and seed set in 17 populations of the rare, self‐compatible, bumblebee‐pollinated perennial Gentiana pneumonanthe L. in the Netherlands. Population size and offspring heterozygosity were used as population properties; grass and heath cover, soil concentrations of various ions, soil acidity (pH), and soil moisture were used as habitat characteristics. Our aim was to find out how important population size and genetic variation are for the seed production of a rare plant, when accounting for a number of habitat parameters that might also be important for successful reproduction. Correlation coefficients between population and habitat characteristics showed that sites with low soil moisture and higher concentrations of most nutrients have a higher cover of grasses and a low cover of heath species. At such sites the population size of G. pneumonanthe was small and offspring heterozygosity was low. The number of ovules per fruit (a component of reproductive effort) was negatively associated with heterozygosity, phosphorus, and pH and positively associated with calcium, potassium, SO 4 , NH 4 , and electric conductivity. Total vegetation cover correlated positively with the variation in ovule production among individuals. Seed set and number of viable seeds per fruit, indicators of the success of fertilization and seed maturation, correlated positively with population size, the cover of co‐flowering heath species, and the same group of nutrients that (independently) had a positive effect on ovule production. A high NO 2 concentration might be toxic because it had a negative effect on the number of viable seeds. Seed weight seemed to be independent of any population or habitat parameter. Besides lower mean values, we also found more variation in reproductive success among individuals in smaller populations. We conclude that plants in small populations of G. pneumonanthe have a similar reproductive potential per flower but have lower seed production and a higher uncertainty of successful reproduction than plants in large populations. Genetic variation was apparently not very important. In addition to population size, habitat characteristics also seemed to be important for seed production and seed set. The most important factors were the facilitating effect of the presence of other insect‐pollinated species and the concentrations of specific nutrients in the soil. To restore small populations, we advise small‐scale sod cutting around the remaining reproductive individuals. This simultaneously allows germination and seedling establishment of G. pneumonanthe , removes soil nutrients, and restores the cover of pollinator‐attracting heath species at the cost of grasses. Relaciones entre Características Poblacionales y del Habitat y la Reproducción de la Especie Rara Gentiana pneumonanthe L. Investigamos las relaciones entre un número determinado de características poblacionales y de sitio y la producción de óvulos y semillas en 17 poblaciones de la especie de hierba rara, autocompatible, polinizada por abejas y perenne Gentiana pneumonanthe L. en los Países Bajos. Utilizamos el tamaño poblacional y la heterocigosidad de la progenie como propiedades poblacionales, la cobertura de gramíneas y ericáceas en Ia vegetación y la concentración de algunas sustancias nutritivas en el suelo fueron usadas como características bióticas y abióticas del hábitat. Nuestra meta fue la de encontrar que tanta importancia tienen el tamaño poblacional y la variación genética en la producción de semillas de una planta rara, tomando en consideración un número de parámetros del hábitat que pueden ser importantes para una reproducción exitosa. Los coeficientes de correlación entre las características poblacionales y del hábitat mostraron que los sitios con grado de humedad bajo y concentraciones de nutrientes altas tienen una cobertura de grarmíneas elevada y de ericáceas reducida. En tales sitios, el tamaño poblacional de G. pneumonanthe es más pequeño y la heterocigosidad de las progenies es más baja. La producción potencial de semillas (medida en forma de número de óvulos por fruto) tenía una relación negativa con la heterocigosidad, la concentración de P y el pH del suelo y una relación positiva con las concentraciones de Ca, K, SO 4 y NH 4 y la conductividad eléctrica. Se encontró una correlación positiva entre la variación del número de óvulos y la cobertura total de la vegetación. El éxito de la fecundación y la maduración de semillas estuvo correlacionado positivamente con el tamaño poblacional, la cobertura de las ericáceas (que florecen simultáneamente) en la vegetación y el mismo grupo de nutrientes que (independientemente) surtían efecto positivo en el número de óvulos. La concentración de NO 2 en el suelo mostró una correlación negativa con el número de semillas viables. También Ia variación en el éxito reproductivo fue más alta en las poblaciones pequeñas. No se encontró relación significativa entre el peso de las semillas y alguna de las características de la población o del hábitat. En base a relaciones observadas, concluimos que las poblaciones pequeñas de Gentiana pneumonanthe tienen el mismo potencial reproductivo por flor, pero tienen una menor producción de semillas y una mayor incertidumbre reproductiva en comparación con las poblaciones grandes. Los factores importantes para el éxito reproductivo son el tamaño poblacional, el efecto facilitador de la presencia de otras especies de hierbas polinizadas por insectos y la disponibilidad de sustancias nutritivas específicas en el suelo. Recomendamos la eliminación en pequeña escala del césped en los alrededores de los adultos reproductivos remanentes para restaurar pequeñas poblaciones. Este método hace posible al mismo tiempo la germinación y el establecimiento de individuos nuevos, remueve nutrientes del suelo y restablece la covertura de especies atrayentes de polinizadores.

Rehabilitation of Oiled Wildlife - David A. Jessup (Conservation Biology, 1998)

Forest Fire Prediction and Prevention in the Brazilian Amazon - Daniel Nepstad; Adriana Moreira; Adalberto Verissimo; Paul Lefebvre; Peter Schlesinger; Christopher Potter; Carlos Nobre; Alberto Setzer; Thelma Krug; Ana Cristina Barros; Ane Alencar; Joao Raposo Pereira (Conservation Biology, 1998)

Letters - Manuel R. Guariguata; Reinmar Seidler; Kamal S. Bawa (Conservation Biology, 1998)

True International Collaboration: Now or Never - Rodrigo A. Medellin (Conservation Biology, 1998)

Propensity for Fire in Guianan Rainforests - David S. Hammond; Hans ter Steege (Conservation Biology, 1998)

Forest Fires in the Brazilian Amazon - Mark A. Cochrane; Mark D. Schulze (Conservation Biology, 1998)

Perspectives on Wildfire in the Humid Tropics - Christopher Uhl (Conservation Biology, 1998)

Forest Fires in the Brazilian Amazon - Mark A. Cochrane; Mark D. Schulze (Conservation Biology, 1998)

Letters - Manuel R. Guariguata; Reinmar Seidler; Kamal S. Bawa (Conservation Biology, 1998)

Comparative dietary analysis of a recently described fish species complex (Galaxiidae) in a New Zealand river - Richard M. Allibone; Colin R. Townsend (New Zealand Journal of Marine and Freshwater Research, 1998)
The diets of several populations of four recently described species of galaxiid with allopatric distributions were examined in the Taieri River, New Zealand. Comparisons of available prey items and prey consumed were carried out to examine whether the distributions of the galaxiid species might be influenced by food availability and preferences. Seventy‐three prey categories were identified. The availability of four of these (Deleatidium, Oligochaeta, Elmidae larvae and adults) differed among the streams occupied by different galaxiid species. Three differences in the frequency of prey consumption (Deleatidium, Oxyethira, and Elmidae larvae) were detected. Despite differences in diet it was concluded that all four fish species were generalist predators of invertebrates with similar diets that were influenced mainly by prey availability. Furthermore prey availability was not considered responsible for the allopatric distribution of the four species, rather, spawning habitat availability, physical nature of the streams, and prior geological history of the Taieri catchment are considered the controlling influences on galaxiid distribution.

The East Cape Current and two eddies: A mechanism for larval retention? - Stephen M. Chiswell; Dean Roemmich (New Zealand Journal of Marine and Freshwater Research, 1998)
Current meters deployed near East Cape, New Zealand, for 1 year show large differences between the offshore flow and that inshore of the 1000 m isobath. Offshore, mean flows are to the south‐east, and are the East Cape Current. Inshore, mean flows are to the north‐east, indicating that there may be a persistent inshore counter current. Comparison between the offshore current meter measurements and geostrophic currents inferred from TOPEX/Poseidon altimetry shows good agreement. We use this agreement to argue that passive drifter trajectories can be modelled using the altimeter data. By simulating drifter releases into the region, and modelling their trajectories, we develop a statistical picture of likely retention times for passive drifters. Drifters can get retained in one or other of two permanent eddies: the East Cape and Wairarapa Eddies, and retention within the system can be as high as 2–3 years, but depends on release time and location. If weak‐swimming larvae such as rock lobster larvae behave as passive drifters, retention and recirculation within the eddies may provide a mechanism allowing them to survive within the system long enough to recruit as juvenile lobsters.

Age and growth of New Zealand school shark, Galeorhinus galeus - Malcolm P. Francis; Kevin P. Mulligan (New Zealand Journal of Marine and Freshwater Research, 1998)
School shark, Galeorhinus galeus (family Triakidae), are fished commercially throughout New Zealand, and estimates of their growth rate, age at maturity, and longevity are required for fishery management. We aged school shark from X‐rays of thin vertebral sections, but many sections were unclear and ageing precision was low. Nevertheless, there was no between‐reader bias, and growth curves derived from length‐at‐age data appear robust. A growth curve was derived independently from length‐frequency data for juvenile school shark up to 9 years old and 120 cm long, and it agreed well with the curve derived from length‐at‐age data. For older sharks, the growth rate is not certain because of small sample sizes and lack of validation of the ages. Growth rate estimates from tag‐recapture data suggested faster growth for small sharks and slower growth for large sharks. Based on length‐at‐age data, males and females grew at about the same rates. Males matured at about 12–17 years and females at about 13–15 years. The oldest shark in our samples was estimated to be 25 years old, but few large sharks were available for ageing so the longevity of New Zealand school shark remains uncertain.

Application of natural and artificial fallout radionuclides to determining sedimentation rates in New Zealand lakes - N. E. Whitehead; R. G. Ditchburn; W. J. McCabe; W. J. Mason; J. Irwin; R. A. Pickrill; G. R. Fish (New Zealand Journal of Marine and Freshwater Research, 1998)
Sedimentation rates have been estimated for New Zealand Lakes Rotoiti, Taupo, Ngahewa, Tikitapu, Okareka, Pukaki, Rotorua, Waikaremoana, Wakatipu, Tekapo, and Ohau, and also the Falls Dam, Central Otago, the Pauatahanui inlet (Wellington), and Lake Vanda (Antarctica). Sedimentation rates were able to be calculated using the 210 Pb and 210 Po methods in 26 out of 28 cores. For the 137 Cs method (shown equivalent to the previous methods) calculable rates were obtained in 13 out of 19 cores. An age estimation was always possible by one of the methods. Values of 147 Pm and 144 Ce showed that most surface layers were undisturbed, hence the hypothetical mixing often invoked to explain 137 Cs profiles lacking the expected 1965 peak is incorrect for most of these cores. Deficits in surface layer 210 Pb caused by 222 Rn loss did not affect the estimates of sedimentation rate. One core contained a record dated back to 1800 A.D. Deposition rates of 210 Pb depended on rainfall, not river input. Some local geothermal activity emits 222 Rn and deposits more 210 Pb than usual for New Zealand lakes, but otherwise absolute 210 Pb levels are generally very low compared to other studies. Deposition rates varied from a low of 0.11 kg m‐ 2 yr‐1 (Lake Tikitapu) to a high of 28 kg m‐ 2 yr‐ 1 (one Lake Pukaki core).

Microform bed clusters as refugia for periphyton in a flood‐prone headwater stream - S. N. Francoeur; B. J. F. Biggs; R. L. Lowe (New Zealand Journal of Marine and Freshwater Research, 1998)
Flood effects on benthic algal communities grown upon three common substratum types were assessed in a gravel‐bed stream. Microform bed clusters (MBCs) and, to a lesser extent, boulders conferred resistance on their associated periphyton communities (i.e., reduced flood‐induced biomass loss; functioned as refugia) relative to cobble/gravel substrata. On all substrata, flooding significantly reduced the relative abundance of Diatoma hiemale , and increased the relative abundance of Gomphonema minutum f. syriacum and/or Ampithrix sp. Long‐term (>4 months) sampling indicated that MBCs generally supported more algal biomass than did boulders, which, in turn, supported greater biomass than cobbles/gravels. Manipulation of the abundance of refugial structures (e.g., MBCs) could possibly alter productivity of flood‐prone gravel‐bed streams. Stream periphyton biomass models may be improved by explicit consideration of the effects of refugial substrata. The interstitial spaces of MBCs may constitute a unique habitat, and deserve further study.

Revision of the genus Psammocinia (Porifera: Demospongiae: Dictyoceratida), with six new species from New Zealand - Steve de C. Cook; Patricia R. Bergquist (New Zealand Journal of Marine and Freshwater Research, 1998)
The status of species within the dictyo‐ceratid sponge genus Psammocinia is reviewed. The separation of Psammocinia species from the closely related Ircinia species, which has been the subject of some dispute, is clarified. This distinction made on the basis of morphological evidence is supported by the limited chemotaxonomic and molecular phylogenetic data available. Six new species of Psammocinia are described from the New Zealand region.

Pigment fluxes from the Subtropical Convergence region, east of New Zealand: Relationships to planktonic community structure - Scott Nodder; Mark Gall (New Zealand Journal of Marine and Freshwater Research, 1998)
A preliminary sediment trap study using photo synthetic pigments as biomarker tracers of pelagic food web processes was conducted in three different water types (subantarctic, Subtropical Convergence, and subtropical), east of New Zealand, in winter and spring 1993. The presence of undegraded pigments in trap samples from water depths of 100–550 m indicate that phytoplankton cells were removed rapidly from surface waters, presumably mainly as sinking intact phytoplankton chains, marine aggregates, or as unconverted pigments in zooplankton waste products. Average pigment budget estimates indicate that 1 of chlorophyll a standing stock and 1 chlorophyll a standing stock and 20–194% primary production) was potentially the most important process affecting particle retention in the upper water column and hence pigment fluxes across all three water types. Bacterial degradation, mesozooplankton grazing, and seasonal stratification were potentially important in subtropical waters in spring.

Dietary composition of Gambusia affinis (Family Poeciliidae) populations in the northern Waikato region of New Zealand - S. Mansfield; B. H. Mcardle (New Zealand Journal of Marine and Freshwater Research, 1998)
Invertebrates were collected and identified from the stomach contents of eight mosquitofish (Gambusia affinis) populations in the northern Waikato region of New Zealand at 3‐month intervals from December 1994 to September 1995. To investigate temporal and spatial patterns in dietary composition a novel analysis programme was created that used Gower's similarity coefficient. The analysis found differences in diet among months, lakes, and three size groups of mosquitofish (≤15, 15–25, and ≥25 mm). Smaller mosquitofish fed mostly on zooplankton whereas larger G. affinis ate greater quantities of terrestrial fauna and large invertebrates. These differences are probably correlated with gape size and visual acuity, although ecological factors may also be important.

Numerical investigation into the effect of freshwater inputs on the circulation in Pelorus Sound, New Zealand - Roger Proctor; Mark Hadfield (New Zealand Journal of Marine and Freshwater Research, 1998)
Observations collected in Beatrix Bay, a small bay within Pelorus Sound, New Zealand, show that although the bay is thermally stratified for much of the year, salinity stratification as a result of intermittent rainfall and river inflow plays a dominant role in the density structure and circulation within the Bay. A 3‐dimensional baroclinic model of Pelorus Sound is developed and applied to the simulation of idealised pulses of rainfall and river inflow to investigate their impact on the density structure and circulation within Pelorus Sound, focusing on Beatrix Bay. The model shows that the rainfall causes near‐surface salinity stratification of 1–2 psu, sufficient to introduce phase differences of c. 2 h between surface and bottom M 2 tidal currents. Following the river inflow, a surface tongue of fresher water is seen to propagate towards the mouth of the Sound, taking c. 4.5 days to reach Beatrix Bay, by which time tidal stirring in the Sound has caused the fresh water to become almost well‐mixed.

The Limits of Nature and the Educational Nature of Limits - David W. Orr (Conservation Biology, 1998)

Effects of Introduced Bullfrogs and Smallmouth Bass on Microhabitat Use, Growth, and Survival of Native Red‐Legged Frogs ( Rana aurora ) - Joseph M. Kiesecker; Andrew R. Blaustein (Conservation Biology, 1998)
We examined the direct and indirect effects of two introduced species, the bullfrog ( Rana catesbeiana ) and smallmouth bass ( Micropterus dolomieui ), on the microhabitat use, growth, development, and survival of larval and metamorphic red‐legged frogs ( Rana aurora ). In field enclosure experiments, tadpoles of R. aurora altered their microhabitat use in the presence of both species. The shift in microhabitat use by R. aurora corresponded to increased activity in adult R. catesbeiana . Time to metamorphosis increased and mass at metamorphosis decreased when R. aurora tadpoles were exposed to either larval or adult R. catesbeiana . In contrast, smallmouth bass alone had little effect on the growth and development of R. aurora . In all experiments, survivorship of R. aurora was significantly affected only when R. aurora were exposed to the combined effects of bullfrog larvae and adults or bullfrog larvae and smallmouth bass. Thus, the interaction between stages (larval‐adult) or species (bullfrog–smallmouth bass) produced indirect effects that were greater than when each factor was considered separately. Efectos de la Introducción de la Rana toro Rana catesbeiana y el Pez Micropterus dolomieui en el Uso del Microhabitat, Crecimiento y Supervivencia de la Rana patiroja Rana aurora Examinamos los efectos directos e indirectos de dos especies introducidas; la rana toro Rana catesbeiana y el pez Micropterus dolomieui en el uso del microhabitat, crecimiento, desarrollo y supervivencia de la Rana patiroja Rana aurora en estados larvales y metamórficos. En encierros experimentales de campo, los renacuajos de R. aurora alteraron el uso de su microhábitat en presencia de ambas especies. El cambio en uso de microhábitat por R. aurora correspondió con un incremento en la actividad de adultos de R. catesbeiana . El tiempo de metamorfósis incrementó y la masa durante metamorfósis disminuyó cuando los renacuajos de R. aurora fueron expuestos tanto a larvas como adultos de R. catesbeiana . En contraste, la presencia de solo Micropterus dolomieui tuvo poco efecto en el crecimiento y desarrollo de R. aurora . En todos los experimentos la supervivencia de R. aurora fue significativamente afectada solo cuando R. aurora estuvo expuesta a los efectos combinados de larvas y adultos de la rana toro y el pez. Por lo tanto, la interacción entre estados (larval/adulto) o especies ( rana toro /Micropterus) produjo efectos indirectos que fueron mayores que cuando cada factor se consideró por separado.

The Role of Migratory Waterfowl as Nutrient Vectors in a Managed Wetland - D. M. Post; J. P. Taylor; J. F. Kitchell; M. H. Olson; D. E. Schindler; B. R. Herwig (Conservation Biology, 1998)
Dense aggregations of waterfowl, often caused by loss of native wetlands and increased waterfowl numbers, can result in the destruction of wetland vegetation and agricultural crops, increase the risk of infectious disease outbreaks, and decrease water quality. Problems related to water quality may be particularly severe in arid regions of the southwestern United States, where water quality and quantity are contentious issues. Over 40,000 Lesser Snow Geese ( Chen caerulescens caerulescens ) and Ross’ Geese ( Chen rossii ) winter annually at Bosque del Apache National Wildlife Refuge, New Mexico. Daily feeding bouts by geese move large quantities of nutrients from farm fields where they feed to managed wetlands where they roost. Using energy and mass balance models, population estimates, daily and seasonal migration patterns, and feeding behaviors, we estimated the mass and ratio of nitrogen to phosphorus of nutrients loaded by geese into the wetlands of the Bosque del Apache National Wildlife Refuge. Loading rates peaked in late November 1995 at more than 300 kg nitrogen per day and over 30 kg phosphorus per day. As feeding behaviors changed through the winter and bird densities declined, loading rates fell. Our estimates suggest that in the winter of 1995–1996, bird‐borne nutrients supplied nearly 40% of the nitrogen and 75% of the phosphorus entering the primary wetland used for geese roosting. High loading rates by geese are a consequence of their colonial roosting behavior; over 90% of the geese roost on 10% of the wetland area. The effects of nutrient loading could be reduced by increasing flushing rates or dispersal of roosting waterfowl. The loss of natural wetlands, however, limits options for expanding wetland area available to waterfowl, and it may be difficult to increase flushing rates in this arid region. Thus, management of waterfowl and the nutrients they move will continue to be an important issue for wetlands of wildlife refuges. El Papel de las Aves Acuáticas como Vectores de Nutrientes en un Humedal Manejado Densas agregaciones de aves acuáticas causadas frecuentemente por la pérdida de humedales nativos y el incremento en el número de ave acuáticas, puede resultar en la destrucción de la vegetación de humedales y cultivos, un incremento en el riesgo de dispersión de enfermedades infecciosas y una disminución en la calidad del agua. Los problemas relacionados con la calidad del agua pueden ser particularmente problemáticos en regiones áridas del suroeste de los Estados Unidos, en donde la calidad y cantidad del agua son temas polémicos. Cerca de 40,000 ganzos Lesser snow ( Chen caerulescens caerulescens ) y ganzos Ross ( Chen rosii ) invernan anualmente en el Refugio de vida silvestre Bosque del Apache, en Nuevo Mexico. Diariamente grandes cantidades de nutrientes son trasladadas de las granjas donde los ganzos se alimentan an los humedales donde descansan. Mediante el uso de modelos de energía y balance de masas, estimaciones de la población, patrones de migración diaria y estacional y conductas alimenticias, estimamos la masa y proporción nitrógeno:fósforo de los nutrientes descargados por los ganzos en los humedales del Bosque del Apache. Las tasas de descarga tuvieron picos al final de Noviembre de 1995 de> 300 kg de nitrógeno y> 30 kg de fósforo por dia. Como la conducta alimenticia cambió a lo largo del invierno y las densidades de aves disminuyeron, las tasas de descarga cayeron. Nuestras estimaciones sugieren que en el invierno de 1995–1996 los nutrientes de origen avícola aportaron cerca del 40% del nitrógeno y 75% del fósforo que entró al humedal mayormente utilizado por los ganzos para descanso. Altas tasas de descarga por ganzos son consecuencia de su conducta de descanso en colonias;> 90% de los ganzos descanzó en solo 10% del área del humedal. Los efectos de descarga de nutrientes podrían ser reducidos incrementando las tasas de flujo o la dispersión de las aves en descanzo. La pérdida de humedales naturales limita de cualquier manera las opciones para expander el área de humedal disponible para las aves, además de que un incremento de las tasas de flujo puede ser dificil en esta árida región. Por lo tanto, el manejo de las aves y los nutrientes que mueven continuará siendo un problema importante para los humedales en refugios de vida silvestre.

A Biologist’s Perspective on the Role of Sustainable Harvest in Conservation - Thomas T. Struhsaker (Conservation Biology, 1998)

Effects of Introduced Bullfrogs and Smallmouth Bass on Microhabitat Use, Growth, and Survival of Native Red-Legged Frogs (Rana aurora) - Joseph M. Kiesecker; Andrew R. Blaustein (Conservation Biology, 1998)

Reintegrating Ecology and Economics - David N. Bengston; Thomas H. Kunz; Philip Cafaro; Jennifer Smith; Lisa L. Manne; Mary Meagher (Conservation Biology, 1998)

Spatial Fidelity of Plant, Vertebrate, and Invertebrate Assemblages in Multiple-Use Forest in Eastern Australia - Ian Oliver; Andrew J. Beattie; Alan York (Conservation Biology, 1998)

Global Patterns of Species Richness: Spatial Models for Conservation Planning Using Bioindicator and Precipitation Data - David L. Pearson; Steven S. Carroll (Conservation Biology, 1998)

Population Aggregation Analysis of Three Caviar‐Producing Species of Sturgeons and Implications for the Species Identification of Black Caviar - Vadim J. Birstein; Phaedra Doukakis; Boris Sorkin; Rob DeSalle (Conservation Biology, 1998)
We describe a reliable method for the identification of the species source for caviar. The assay is based on the identification of diagnostic nucleotide positions in the mitochondrial cytochrome b gene from a sequence database of 20 of 25 living sturgeon species. The collection of attribute data is polymerase chain reaction (PCR)‐based and can readily identify the character states of several diagnostic nucleotide positions in the cytochrome b gene for the three main commercial species of caviar‐producing sturgeons ( Acipenser gueldenstaedtii , A. stellatus , Huso huso ). Over 20 individuals from each of the three species from a wide range of geographic regions were used to determine which of the potentially informative sites are diagnostic of phylogenetic lineages through use of the population aggregation analysis method. We also report results from a survey of 95 lots of commercially available caviar in the New York City area. Overall, 23% of the designations made by caviar suppliers were mislabeled with respect to species identification. Recent declines in population size of the three commercial species, combined with an increase in the demand for caviar on the international market, could have caused the observed mislabeling. Replacement of commercial species with endangered and threatened species indicates possible illegal harvest and poaching; action should be initiated to ensure the survival of all threatened Acipenseriformes. The use of our PCR assay might aid in conservation efforts in the United States and internationally. Análisis de Agregación de Poblaciones de Tres Especies de Esturiones Productoras de Caviar y sus Implicaciones en la Identificación de Especies de Caviar Negro Describimos un método confiable para la identificación de las especies fuente de caviar. La prueba se basa en la identificación de posiciones diagnóstico de nucleótidos en el gen citocromo b de una base de datos de secuencias de 20 de las 25 especies de esturiones vivientes. La colección de datos se basa en PCR y puede identificar fácilmente los estados de diversas posiciones diagnóstico de nucleótidos del gen citocromo b de las tres especies comerciales de esturiones mas importantes productoras de caviar ( Acipenser gueldenstaedtii , A. stellatus y Huso huso ). Cerca de 20 individuos de cada una de las tres especies provenientes de un amplio rango de regiones geográficas fueron usados para determinar cuales de los sitios potenciales de información sirven como diagnóstico de linajes filogenéticos, usando el método de análisis de agregación poblacional. Tambien reportamos resultados de un estudio de 95 lotes de cavier comercialmente disponible en el área de la ciudad de Nueva York. Alrededor de un 23% de las designaciones realizadas por los proveedores de caviar estuvieron mal etiquetadas con respecto a la identificación de especies. Recientes disminuciones en los tamaños poblacionales de las tres especies comerciales combinadas con un incremento en la demanda de caviar en el mercado internacional han causado la mala etiquetación observada. La renovación de especies comerciales por especies en peligro o amenazadas es un indicativo de la posible cosecha y sacrificio ilegal, se deberán iniciar acciones para asegurar la supervivencia de todos los Ascipensiformes amenazados. El uso de nuestro análisis de PCR podría contribuir con los esfuerzos de conservación en los Estados Unidos e internacionalmente.

Spatial Fidelity of Plant, Vertebrate, and Invertebrate Assemblages in Multiple‐Use Forest in Eastern Australia - Ian Oliver; Andrew J. Beattie; Alan York (Conservation Biology, 1998)
The design of a protected areas network that contains or represents as many species as possible (maximum complementarity of areas) is a first step toward in situ conservation of species biodiversity. In the absence of complete species inventories, however, area selection must employ surrogate data such as the distribution of plant or vertebrate species. The degree to which the use of these taxa results in a network of sites with maximum complementarity for others depends on levels of assemblage fidelity among taxa. Assemblage fidelity is defined here as the degree to which assemblages from different phylogenic groups co‐occur in space and time. We examined the spatial fidelity of ground‐active invertebrate (ants and several beetle families: Carabidae, Scarabaeidae, Pselaphidae), vascular plant, and vertebrate assemblages (birds, small mammals, frogs, and reptiles) at 56 sites in a range of eastern Australian forest types. We used unlogged ( n = 32) and logged ( n = 24) forest sites. Assemblage fidelity was assessed by ordination and Mantel correlation, and patterns of species richness and species turnover that helped explain the findings were analyzed by simple correlation, cluster analysis, and two indices of β diversity. Our analyses revealed general assemblage fidelity among plant, vertebrate, and invertebrate assemblages, and results were consistent in both unlogged and logged forest. In several forest types, however, fidelity among invertebrates and plants was low due to high invertebrate turnover. Overall levels of species turnover were much higher for vascular plants and invertebrates than for vertebrates. Species richness patterns at individual sites were generally uncorrelated among taxa. Our findings suggest that (1) the exclusion of invertebrates from biodiversity surveys cannot be justified on the assumption that plant and vertebrate assemblages act as surrogates for invertebrate species‐level biodiversity or on the basis of cost‐efficiency; (2) both spatial fidelity and species turnover are useful for evaluating the role of selected taxa as surrogates for the species‐level biodiversity of others; (3) the selection of sites for in situ biodiversity conservation should consider taxa that exhibit high levels of species turnover; and (4) the inclusion of invertebrates in biodiversity surveys may offer considerable cost savings and be more representative of species biodiversity than conventional plant and vertebrate surveys. Fidelidad Espacial de Ensamblajes de Plantas, Vertebrados e Invertebrados en Bosques de usos Múltiples en Australia Oriental El diseño de redes de áreas protegidas que contengan o representen tantas expecies como sea posible (complementaridad máxima de áreas) es un primer paso hacia la conservación in situ de la biodiversidad de especies. Sin embargo, en ausencia de inventarios de especies completos, la selección del área deberá emplear datos alternativos como son la distribución de especies de plantas o vertebrados. El grado de resultado del empleo de estos datos en una red de sitios con máxima complementaridad para con otros dependerá del nivel de fidelidad del ensamblaje entre datos. La fidelidad del ensamblaje se define aquí como el grado con el cual los ensamblajes de diferentes grupos filogenéticos co‐ocurren en espacio y tiempo. Examinamos la fidelidad espacial de invetebrados activos del suelo (hormigas y varias familias de escarabajos: Carabidae, Scarabaeidae, Pselaphidae), plantas vasculares y ensamblajes de vertebrados (aves, mamiferos pequeños, ranas y reptiles) en 56 sitios de un rango de bosques de Australia oriental. Utilizamos sitios con bosques no talados ( n = 32) y talados ( n = 24). La fidelidad del ensamblaje se evaluó por medio de ordenación y correlación de Mantel, los patrones de riqueza y renovación de especies que ayudaron a explicar los resultados fueron analizados mediante correlación simple, análisis de conglomerados (clusters) y dos indices de diversidad β. Nuestros análisis revelan una fidelidad general entre esamblajes de plantas, vertebrados e invetebrados y que los resultados son consistentes tanto en areas taladas como en no taladas. Sin embargo, en diversos tipos de bosques, la fidelidad entre invertebrados y plantas fue baja debido a una elevada tasa de renovación de invertebrados. En general, los patrones de riqueza de especies en sitios individuales no estuvieron correlacionados entre taxas. Nuestros resultados sugieren que: (1) la exclusion de invertebrados de los estudios de biodiversidad no puede ser justificada bajo la aserveración de que los ensamblajes de plantas y vertebrados actúan como indicadores alternativos de biodiversidad para el nivel de especies de invertebrados, ni en base a costo‐eficiencia; (2) tanto la fidelidad espacial como la tasa de renovación son valiosos para la evaluación del papel de los taxas seleccionados como alternativos para la biodiversidad a nivel de especie de otros taxas; (3) la selección de sitios para la conservación de la biodiversidad in situ, deberá considerar taxas que exhiban niveles altos de renovación de especies y (4) la inclusión de invertebrados en estudios de biodiversidad podría ofrecer ahorros considerables en costos a la vez de ser mas representativos de la biodiversidad de especies que los estudios convencionales de plantas y vertebrados.

Identifying Populations for Conservation on the Basis of Genetic Markers - Remy J. Petit; Abdelhamid El Mousadik; Odile Pons (Conservation Biology, 1998)

A Transportation Model Assessment of the Risk to Native Mussel Communities from Zebra Mussel Spread - Daniel W. Schneider; Christopher D. Ellis; Kevin S. Cummings (Conservation Biology, 1998)
When introduced species threaten native flora and fauna, protection requires an analysis of the risk that native species face from the spread of the introduced species. Models of invading species, however, often do not include a dynamic component of risk. North American freshwater mussels are at risk of fouling by the introduced zebra mussel ( Dreissena polymorpha ). Predictions of the risk to native mussel communities of invasion by the zebra mussel can help prioritize conservation efforts. We present a model for the spatial analysis of zebra mussel spread that allows the characterization of relative risk of infestation to the high‐quality mussel communities of Illinois streams. A gravity model, constrained at origin and destination, was parameterized with data on boat use at 120 boat landings in Illinois. The risk of spread of zebra mussels depends on the number of boat trips from infested waters, which in turn depends on distance from an infested water, boat use at a site, and the position of a lake within a river system. Habitats supporting a high diversity of native mussels and threatened and endangered species are at risk of infestation from reservoirs upstream. Invasion of inland lakes and reservoirs in Illinois is predicted to occur first at areas of high boat use close to currently infested waters, including the Fox Chain of Lakes, followed by central Illinois reservoirs. These reservoirs will act as stepping stones, facilitating the invasion of lakes upstream of critical native mussel habitats. Efforts to protect waters that center on prevention of the initial invasion of stepping‐stone lakes could significantly reduce the risk of infestation. Education and inspection efforts are predicted to be more effective than quarantine because quarantines would displace boat traffic to critical habitats. The class of models presented here is useful for predicting risk of invasion when complete data on vector movement are not available. Evaluación de Riesgo de un Modelo de Transportación para Comunidades Nativas de Mejillones Debido a la Dispersión del Mejillon Zebra Cuando las especies introducidas amenazan la flora y fauna nativa, la protecci ó n requiere de un análisis del riesgo que las especies nativas enfrentan debido a la disperción de las especies introducidas. Sin embargo, los modelos de invasi ó n de especies frecuentemente no incluyen un componente dinámico de riesgo. Los mejillones de Norteamérica se encuentran en riesgo de ser entampados por el mejill ó n zebra introducido ( Dreissena polymorpha ). Las predicciones de riesgo para las comunidades nativas de mejillones podrían ayudar a priorizar los efuerzos de conservación. Presentamos un modelo de análisis espacial de la dispersión del mejillón zebra que permite la caracterización del riesgo relativo de infestación de comunidades de mejillones de alta calidad de los arrollos de Illinois. Un modelo de gravedad, forzado en el origen y destino, se parametrizó con datos de uso de botes en 120 arribos en Illinois. El riesgo de dispersión del mejillón zebra depende del número de viajes de boes a zonas infestadas, que a su vez depende de la distancia a la que se encuentran las aguas infestadas, el uso del bote en el sitio y la posición del lago dentro del sistema riverino. Los hábitats que soportan una gran diversidad de mejillones nativos y de especies amenazadas o en peligro se encuentran en riesgo de infestación por los reservorios aguas arriba. Se predice que la invasión de lagos y reservorios tierra adentro en Illinois, ocurriría primero en áreas con un alto uso de botes, cercanas a las zonas actualmente infestadas incluyendo la cadena de Lagos Fox, seguido de los reservorios del centro de Illinois. Estos reservorios actuarían como trampolines, facilitando la invasión de lagos rio arriba, con hábitat crítico para especies de mejillones nativos. Los esfuerzos para proteger las aguas que se centren en la prevención de la invasión inicial de lagos‐trampolín podría reducier significativamente el riesgo de infestación. Se predice que la educación e inspección de esfuerzos serían mas efectivos que las cuarentenas, puesto que las cuarentenas podrían desplazar el tráfico de botes hacia hábitats críticos. La clase de modelos presentados en este trabajo son de gran uso para la predicción de riesgos de invasión cuando los datos de vector de movimiento no se encuentran a la mano.

Autocorrelated Rates of Change in Animal Populations and their Relationship to Precipitation - Bradley J. Swanson (Conservation Biology, 1998)
I examined the prevalence of autocorrelation in mammalian, avian, and precipitation time series, how well autocorrelation in the environment translates into autocorrelation in animal populations, and length of the time series needed to accurately characterize the degree of autocorrelation. These are important questions because more‐complex population models are incorporating autocorrelation terms in life‐history characteristics and the intrinsic rate of increase. Including inaccurate or nonsignificant autocorrelation can alter the conclusions reached, providing either an unduly rosy or bleak picture of the likelihood of population viability and persistence. Using autocorrelation analysis in 175 vertebrate and 88 precipitation data sets, I found that 17.8% of the mammalian time series, 61.5% of the avian time series, and 97.7% of the precipitation data sets were autocorrelated. Carnivore populations were more likely than herbivore populations to show significant autocorrelation at lags of 2 or more years. I found only two cases of significant cross correlation between rate of population increase and local precipitation. This indicates that, although some environmental variables may be highly autocorrelated, it does not translate into autocorrelation in the resident animal populations. Based on subsampling of the precipitation and vertebrate data, I found that 15 years of data is sufficient to produce an autocorrelation not significantly different from one based on 100 years of data, although the variance continues to decrease with the length of the time series, as expected. My results suggest that, although some populations show temporal autocorrelation, it is not ubiquitous, and that environmental autocorrelation may not be a good predictor of autocorrelation in rates of increase. Population modelers should determine if autocorrelation exists in populations of interest prior to modeling their viability or probability of persistence because not all populations are equally influenced by autocorrelation. Tasas de Cambio en Poblaciones de Animales Autocorrelacionadas y sus Relaciones con la Precipitación. Se examinó el predominio de la autocorrelación en series de tiempo de mamíferos, aves y precipitación; que tanto la autocorrelación ambiental se traduce en autocorrelación en poblaciones de animales, así como la longitud de las series de tiempo necesaria para caraterizar con precisión el grado de autocorrelación. Estas son preguntas importantes puesto que los modelos poblacionales mas complejos incorporan la autocorrelación en las características de la historia de vida y la tasa intrínseca de incremento. Aún la inexactitud o autocorrelatción no significativa puede alterar las conclusiones obtenidas, proveyendo indebidamente una idea prometedora o poco promotedora de la probabilidad de viabilidad y persistencia de una población. Mediante el uso del análisis de autocorrelación en 175 juegos de datos de vertebrados y 88 de precipitación, encontré que un 17.8% de las series de tiempo de mamíferos, 61.5% de las series de tiempo de aves y un 97.8% de los datos de precipitación se encontraban autocorrelacionados. Las poblaciones de carnívoros fueron las mas viables a mostrar autocorrelación en lapsos de 2 o mas años que las poblaciones de herbívoros. Encontré solo dos casos de correlación cruzada significativa entre la tasa de incremento poblacional y la precipitación local. Esto indica que aunque algunas variables ambientales pueden estar altamente autocorrelacionadas, no se traduce en una autocorrelación en las poblaciones de animales residentes. Basado en un submuestreo de la precipitación y datos de vertebrados, encontre que 15 años de datos es suficiente para producir una autocorrelación que no es significativamente diferente de aquella basada en 100 años de datos, aunque la varianza continua disminuyendo con la longitud de las series de tiempo a como es de esperarse. Mis resultados sugieren que aunque algunas poblaciones muestran autocorrelación temporal, esta no es evidente y la autocorrelación ambiental podría no ser un buen predictor de autocorrelación de tasas de incremento. Los modeladores de poblaciones deberán determinar si la autocorrelación existe en poblaciones de interés antes de modelar su viabilidad o la probabilidad de persistencia puesto que no todas las poblaciones son afectadas por la autocorrelación de la misma manera.

Genetic Evaluation of a Demographic Bottleneck in the Greater Prairie Chicken - Juan L. Bouzat; Hans H. Cheng; Harris A. Lewin; Ronald L. Westemeier; Jeffrey D. Brawn; Ken N. Paige (Conservation Biology, 1998)
Although the theoretical relationship between population size, fitness, and genetic variation is well established, only a few studies have provided direct evidence that ties a decline in both genetic variation and fitness to a demographic bottleneck for a natural system. We report on a genetic comparison of four populations of the Greater Prairie Chicken ( Tympanuchus cupido ) with different demographic histories. Specifically, we compared a population from Illinois that has suffered an extreme demographic contraction and an associated decline in population fitness (measured in terms of hatchability rates) with populations from Kansas, Nebraska, and Minnesota with no known history of bottlenecks or associated declines in fitness. Using the polymerase chain reaction, we amplified six microsatellite loci from which levels of heterozygosity, allelic diversity, and geographic differentiation ( F ST and R ST ) of the studied populations were estimated. Results of this analysis showed that the Illinois Prairie Chicken had the lowest estimate of mean heterozygosity per locus and approximately two‐thirds the allelic diversity, sharing 95–100% of all their alleles with each of the other populations. This finding suggests that the Illinois Prairie Chicken originally had higher levels of genetic diversity that were subsequently lost through an extreme demographic contraction. To our knowledge this is the first example of loss of genetic diversity being associated with a decrease in population fitness as a result of a known demographic bottleneck in a wild bird species. Evaluación Genética de un Cuello de Botella Demográfico en la Gran Gallineta de la Pradera Aunque la relación teórica entre el tamaño poblacional, la aptitud biológica y la variabilidad genética ha sido bien establecida, son pocos lo astudios que han proporcionado evidencia directa que asocie una disminución de la variación genética y de la aptitud biológica con un cuello de botella demografico en sistemas naturales. Reportamos una comparación genética de cuatro poblaciones de la gran gallineta de la pradera ( Tympanucus cupido ) que tuvieron historias demográficas diferentes. Específicamente comparamos una población de Illinois, la cual ha sufrido una contracción demográfica extrema asociada con decrementos en la aptitud biológica poblacional (medida en términos de tasas de eclosión), con poblaciones de Kansas, Nebraska y Minnesota, las cuales no presentan una historia de cuello de botella poblacional ni decrementos en la aptitud bioloógica. Mediante el uso de la reacción en cadena de la polimerasa (PCR) amplificamos seis marcadores de microsatélites con los cuales estimamos niveles de heterocigósis, diversidad alélica y diferenciación geográfica ( F ST y R ST ) en las poblaciones estudiadas. La gran gallineta de la pradera en Illinois presenta el menor valor de heterocigosidad promedio por locus y aproximademente 2/3 de la diversidad alélica, compartiendo 95–100% de sus alelos con cada una de las otras poblaciones. Estos resultados sugieren que la población de Illinois presentaba originalmente niveles mayores de variabilidad genética, los cuales fueron perdidos consecuentemente a través de un contracción demográfica extrema. A nuestro entender, este estudio representa el primer ejemplo en el que se asocia la pérdida de la diversidad genética en una especie de ave silvestre con la disminución en la aptitud poblacional y como resultado de un cuello de botella demográfico conocido.

New Insights on Cheetah Conservation through Demographic Modeling - Kevin R. Crooks; M. A. Sanjayan; Daniel F. Doak (Conservation Biology, 1998)

Population Aggregation Analysis of Three Caviar-Producing Species of Sturgeons and Implications for the Species Identification of Black Caviar - Vadim J. Birstein; Phaedra Doukakis; Boris Sorkin; Rob DeSalle (Conservation Biology, 1998)

Comparison of Breeding Strategies for Purging Inbreeding Depression via Simulation - Yong-Bi Fu; Gene Namkoong; John E. Carlson (Conservation Biology, 1998)

Modeling Disjunct Gray Wolf Populations in Semi-Wild Landscapes - Robert G. Haight; David J. Mladenoff; Adrian P. Wydeven (Conservation Biology, 1998)

Identifying Populations for Conservation on the Basis of Genetic Markers - Rémy J. Petit; Abdelhamid El Mousadik; Odile Pons (Conservation Biology, 1998)
To select candidate populations of wild species to be given priority for conservation, genetic criteria gained from the study of molecular markers may be useful. Traditionally, diversity measures such as expected heterozygosity or percentage of polymorphic loci have been considered. For conservation we propose instead that priority should be given to measures of allelic richness. To standardize the results of allelic richness across populations, we used the technique of rarefaction. This technique allows evaluation of the expected number of different alleles among equal‐sized samples drawn from several different populations. We also show how the contribution of each population to total diversity can be partitioned into two components. The first is related to the level of diversity of the population and the second to its divergence from the other populations. For conservation purposes the uniqueness of a population—in terms of its allelic composition—may be at least as important as its diversity level. These new descriptors are illustrated by means of isozyme and chloroplast DNA data obtained for an endangered tree species, the argan tree of Morocco ( Argania spinosa (L.) Skeels). With these analyses the conservation value of the argan tree populations, especially those of two isolates present in the north of the country, can be better appreciated. The methods proposed to identify priority areas for conservation of the genetic resources of the argan tree are compared to those sometimes advocated in the case of reserve design, where one of the goals is to maximize species richness. Identificacón de Poblaciones para su Conservación en Base a Marcadores Genéticos Los criterios genéticos obtenidos del estudio de marcadores moleculares podrían ser útiles para seleccionar poblaciones de vida silvestre como candidatos con prioridad para su conservación. Tradicionalmente se consideran medidas de la diversidad como son la heterocigocidad esperada, o el porcentaje de loci polimórficos. Para medidas de conservación, nosotros proponemos en su lugar que la prioridad se enfoque en medidas de riqueza alélica. Para estandarizar los resultados de riqueza alélica entre problaciones, utilizamos una técnica de vacuidad. Esta técnica permite evaluar el número esperado de alelos entre muestras de igual tamaño obtenidas de diferentes poblaciones. Mostramos como la contribución de cada población a la diversidad total puede ser repartida en dos componentes; el primero esta relacionado con el nivel de diversidad de la población y el segundo con su divergencia de las otras poblaciones. Para propósitos de conservación, la singularidad de una población (en forma de composición alélica) puede ser por lo menos tan importante como lo es su nivel de diversidad, Estos nuevos elementos descriptivos son ilustrados mediante el uso de datos de DNA de isozima y cloroplasto para una especie de árbol en peligro, el árbol argan de Morocco ( Argania spinosa (L.) Skeels). Con estos análisis, el valor de conservación de las poblaciones del árbol argan puede ser apreciado mejor, especialmente para aquellas provenientes de dos grupos aislados del norte del país. Los métodos propuestos para la identificación de áreas prioritarias para la conservación de los recursos genéticos del árbol argan son comparados con aquellos utilizados en el diseño de reservas, donde una de las metas es la maximización de la riqueza de especies.

Avian Movements and Wetland Connectivity in Landscape Conservation - Susan M. Haig; David W. Mehlman; Lewis W. Oring (Conservation Biology, 1998)
The current conservation crisis calls for research and management to be carried out on a long‐term, multi‐species basis at large spatial scales. Unfortunately, scientists, managers, and agencies often are stymied in their effort to conduct these large‐scale studies because of a lack of appropriate technology, methodology, and funding. This issue is of particular concern in wetland conservation, for which the standard landscape approach may include consideration of a large tract of land but fail to incorporate the suite of wetland sites frequently used by highly mobile organisms such as waterbirds (e.g., shorebirds, wading birds, waterfowl). Typically, these species have population dynamics that require use of multiple wetlands, but this aspect of their life history has often been ignored in planning for their conservation. We outline theoretical, empirical, modeling, and planning problems associated with this issue and suggest solutions to some current obstacles. These solutions represent a tradeoff between typical in‐depth single‐species studies and more generic multi‐species studies. They include studying within‐ and among‐season movements of waterbirds on a spatial scale appropriate to both widely dispersing and more stationary species; multi‐species censuses at multiple sites; further development and use of technology such as satellite transmitters and population‐specific molecular markers; development of spatially explicit population models that consider within‐season movements of waterbirds; and recognition from funding agencies that landscape‐level issues cannot adequately be addressed without support for these types of studies. Movimientos de Aves y Conectividad de Humedales en la Conservación del Paisaje La actual crísis en la conservación exige de investigación y manejo a desarrollarse en escalas de largo plazo, basada en multiples especies y en espacios grandes. Desafortunadamente, los científicos, manejadores y las agencias frecuentemente ven frustrados sus esfuerzos para conducir estos estudios de gran escala debido a la carencia de tecnología, metodologia y soporte económico apropiados. Este tema es de particular interés en la conservación de humedales donde la perspectiva común de paisaje pudiera considerar un área extensa de tierra pero no incorpora humedales aptos que son frecuentemente usados por organismos con alta movilidad como lo son las aves acuáticas (aves playeras o de vados, ganzos, patos). Tipicamente estas especies tienen dinámicas poblacionales que requiren del uso de multiples humedales, sin embargo, este aspecto de su historia de vida frecuentemente es ignorado en la planeación de su conservación. Resaltamos problemas teóricos, empíricos, de modelado y de planeación asociados con este tema y sugerimos soluciones para algunos obstáculos actuales. Estas soluciones representan un intercambio entre estudios a profundidad de una sola especie y estudios genéricos multiespecie. Estos últimos incluyen el estudio de movimientos de las aves acuáticas entre y dentro estaciones en una escala espacial apropriada tanto para aves de amplia dispersión y especies mas estacionarias; censos en múltiples sitios; desarrollo y uso de tecnología como los transmisores vía satélite y marcadores moleculares específicos de poblaciones; desarrollo de modelos poblacionales espacialmente explícitos que consideren movimientos de las aves acuáticas durante las estaciones y el reconocimiento de las agencias patrocinadoras de que asuntos a nivel de paisaje no podrán ser adecuadamente afrontados sin el apoyo para este tipo de estudios.

Letters - Timothy D. Male; Reed F. Noss; Timothy M. Crowe; Jon Paul Rodríguez; Gary K. Meffe (Conservation Biology, 1998)

An Ecology-Based Method for Defining Priorities for Large Mammal Conservation: The Tiger as Case Study - Eric D. Wikramanayake; Eric Dinerstein; John G. Robinson; Ullas Karanth; Alan Rabinowitz; David Olson; Thomas Mathew; Prashant Hedao; Melissa Conner; Ginette Hemley; Dorene Bolze (Conservation Biology, 1998)

Effectiveness of a Vegetation‐Based Approach to Insect Conservation - Ron Panzer; Mark W. Schwartz (Conservation Biology, 1998)
We used plant and insect data from 50 prairie reserves in the Chicago region to assess the extent to which reliance on plant criteria for conservation planning might result in the conservation of insect biodiversity within the tallgrass prairie ecosystem. Three of nine plant measures—plant community richness, plant species richness, and plant genus richness—were found to explain significant levels of variation in conservative (reserve‐requiring) insect species richness in best‐fit regressions. Native plant species richness explained from 28% to 49% (80–85%, on average, when coupled with area) of the variance in conservative insect species richness among sites, suggesting that plants are a useful indicator taxon. Conservative insect species were well represented within the botanically selected Chicago‐area reserve system, providing additional support for the vegetation‐based “coarse‐filter” preserve selection approach. We found no evidence of concurrence between either conservative plant species richness or rare plant richness and conservative insect species richness, suggesting that the use of additional “fine‐filter” plant data may not increase capture rates for reserve‐requiring insects. Among nine plant measures, only plant community richness showed (limited) promise as a surrogate for rare insect richness. We found no coincidence between either plant species richness or common insect species richness and rare insect species richness, supporting earlier suggestions that a “hot spot” approach might fail to capture rare species at finer spatial scales. Low levels of coincidence between plant family richness and insect species richness suggest that the use of higher taxa for cost‐effective reserve selection may not be an effective conservation strategy. We conclude that a vegetation‐based coarse‐filter approach, emphasizing native plant species and plant community richness, can contribute substantially to the conservation of insect biodiversity in tallgrass prairie regions, and perhaps within temperate regions generally. We caution, however, that effective protection of rare insect species will require a detailed knowledge of their identity and distribution within the region under consideration. Efectividad de un Enfoque de Conservación de Insectos Basado en Vegetación Utilizamos datos de plantas e insectos de 50 reservas de pradera en la región de Chicago para evaluar el grado en que la planeación de conservación basada en plantas se refleje en la conservación de la biodiversidad de insectos en el ecosistema de praderas de pastizales altos. Por medio del mejor ajuste de la regresión encontramos que tres de nueve medidas de plantas (riqueze de comunidades de plantas, riqueza de especies de platas y riqueza de géneros de plantas) explican los niveles significativos de variación en la riqueza de especies de insectos conservadores (que requieren de reservas). La riqueza de especies de plantas nativas explicó del 28% al 49% (80–85%, en promedio, cuando acoplada con el área) de la variación en la riqueza de especies de insectos conservadoras entre sitios, lo cual sugiere que las plantas son un taxón indicator útil. Las especies de insectos conservadores estaban bien representadas en el sistema de reservas en el área de Chicago seleccionadas botánicamente, lo cual proporcionó un argumento adicional para el enfoque de selección de reservas de “filtro grueso” basado en la vegetación. No encontramos evidencia de concurrencia entre la riqueza de especies de plantas conservadoras o la riqueza de plantas raras con la riqueza de especies de insectos conservadores, lo cual sugiere que el uso de datos de “filtro fino” de plantas no incrementa las tasas de captura de insectos que requieren reservas. Entre las nueve medidas de plantas, solo la riqueza de comunidades mostró indicio (limitado) como sustituto de la riqueza de especies de insectos raros. No encontramos coincidencia entre la riqueza de especies de plantas o la riqueza de especies de insectos comunes y la riqueza de especies de insectos raros, lo cual soporta la idea de que el enfoque de “zona álgida” puede no capturar a especies raras en escalas espaciales finas. Los bajos niveles de coincidencia entre la riqueza de familias de plantas y la riqueza de especies de insectos sugiere que el uso de taxa mayores para la selección de reservas efectivas no es una estrategia efectiva de conservación. Concluimos que el enfoque de “filtro grueso” basado en la vegetación, que enfatiza la riqueza de especies de plantas nativas y de comunidades de plantas, puede contribuir substancialmente a la conservación de la biodiversidad de insectos en praderas con pastos altos y, quizás, en general para regiones templadas. Sin embargo, hacemos la advertencia de que la protección efectiva de especies raras de insectos requerirá del conocimiento detallado de su identidad y distribución dentro de la región a considerar.

Evolutionarily Significant Units, Distinct Population Segments, and the Endangered Species Act: Reply to Pennock and Dimmick - Robin S. Waples (Conservation Biology, 1998)

Inbreeding and Extinction: Island Populations - Richard Frankham (Conservation Biology, 1998)

Geographic Isolation of Hector's Dolphin Populations Described by Mitochondrial DNA Sequences - F. B. Pichler; S. M. Dawson; E. Slooten; C. S. Baker (Conservation Biology, 1998)

Status and Restoration Options for Atlantic Sturgeon in North America - John R. Waldman; Isaac I. Wirgin (Conservation Biology, 1998)

The Impact of Individual Tree Harvesting on Thermal Environments of Lizards in Amazonian Rain Forest - Laurie J. Vitt; Teresa C. S. Avila‐Pires; Janalee P. Caldwell; Veronica R. L. Oliveira (Conservation Biology, 1998)
Single‐tree harvesting with on‐site lumber production produces gaps in Amazonian forest canopy that are structurally different from natural treefall gaps. Harvest gaps are much more open, and there is neither leaf litter nor partial shading as in natural treefalls, so these anthropogenic gaps receive more intense sunlight. We used HOBO XT temperature and light data loggers to measure thermal environments in forest patches. These data were combined with data on lizard activity, activity temperatures, and habitat use to determine whether human‐made gaps influence the structure of Amazon forest lizard assemblages. Human‐made treefalls are not only more extreme thermally than surrounding forest habitat patches and natural treefalls, but they are warmer than expected based on increased light alone. Large‐bodied teiid lizards, which are typically uncommon or rare within forest, bask in sun in treefalls to gain heat. The body temperatures of these heliotherms average 36.1° C. Nonheliothermic species avoid treefalls and remain in shade within the forest. Their body temperatures average 27.7° C. Heliothermic lizards using treefall gaps are large‐bodied predaceous species that feed on vertebrates as well as invertebrates. Increasing the number of anthropogenic treefall gaps in a forest may increase the immigration and population growth of heliothermic lizards, thereby increasing their population density. Predation by these lizards and dominance over smaller lizards in interference competition (for food) may have a cascading effect on forest species, changing community structure. Impacto de la Cosecha Individual de Arboles en Ambientes Termales de Lagartijas de Bosques Tropicales Lluviosos del Amazonas La cosecha de árboles individuales con producción de madera en el sitio crea espacios en el dosel del bosque amazónico que son estructuralmente diferentes a los espacios creados por la caída natural de árboles. Espacios por cosecha son mucho mas abiertos y no dejan ni hojarasca, ni sombreado parcial como sucede en la caída natural de árboles, esto ocasiona que estas áreas abiertas por actividades antropogénicas reciban relativamente mayor iluminación solar. Utilizamos colectores de datos de temperatura HOBO XT y de intensidad luminosa para medir ambientes termales en parches del bosque. Estos datos se combinaron con datos de actividad de lagartijas, temperaturas de actividad y uso del hábitat para determinar si los espacios abiertos por humanos influencían la estructura de los ensamblajes de lagartijas del Amazonas. La caída de árboles provocada por humanos no son únicamente mas exstremos térmicamente que los parches de hábitat boscoso circundantes y los espacios abiertos provocados por la caída natural de arboles, sino que fueron mas calientes de lo esperado debido al incremento de la intensidad luminosa. Lagartijas de cuerpo grande poco comunes o raras dentro del bosque se asolean en áreas abiertas para incrementar el calor. Las temperaturas corporales de estas lagartijas heliotérmicas promedian 36.1° C. La mayoría de las especies de lagartijas no heliotérmicas evitan las áreas abiertas y permanecen en la sombra dentro del bosque. Las temperatures corporales de éstas últimas promedia 27.7° C. Las lagartijas heliotérmicas que utilizan los espacios abiertos presentan cuerpos grandes y son especies depredadoras que se alimentan tanto de vertebrados como de invertebrados. El incremento de espacios abiertos ocasionados por actividades antropogénicas en un bosque puede incrementar la inmigración y crecimiento poblacional de lagartijas heliotérmicas, incrementando en consecuencia la densidad poblacional. La depredación de estas lagartijas y su dominio sobre otras lagartijas pequeñas en competencia por interferencia (por alimento) puede tener un efecto de cascada sobre especies del bosque, cambiando la estructura de la comunidad.

Ecosystem Services and the Law - James Salzman (Conservation Biology, 1998)

Predicting Effects of Predation on Conservation of Endangered Prey - A. R. E. Sinclair; R. P. Pech; C. R. Dickman; D. Hik; P. Mahon; A. E. Newsome (Conservation Biology, 1998)
In parts of the world such as the Pacific Islands, Australia, and New Zealand, introduced vertebrate predators have caused the demise of indigenous mammal and bird species. A number of releases for reestablishment of these mammal species in mainland Australia have failed because predators extirpated the new populations. The nature of the decline of both extant populations and reintroduced colonies provides information on the dynamics of predation. Predator‐prey theory suggests that the effects of predation are usually inversely dependent on density (depensatory) when the prey are not the primary food supply of exotic predators. Thus, such predators can cause extinction of endemic prey species. Three types of evidence can be deduced from the predator‐prey interactions that allow predictions for conservation: (1) whether per capita rates of change for prey increase or decrease with declining prey densities, (2) whether predation is depensatory or density‐dependent, and (3) the overall magnitude of predation. If this magnitude is too high for coexistence, then the degree of predator removal required can be predicted. If the magnitude of predation is sufficiently low, then the threshold density of prey that management must achieve to allow predator and prey to coexist can also be predicted. We analyzed published reports of both declining populations and reintroduced colonies of endangered marsupial populations in Australia. The observed predation curves conformed to the predictions of predator‐prey theory. Some, such as the black‐footed rock‐wallaby ( Petrogale lateralis ), were classic alternate prey and were vulnerable below a threshold population size. Others, such as the brush‐tailed bettong ( Bettongia penicillata ), have a refuge at low numbers and thus offer the best chance for reintroduction. Our predictions suggest a protocol for an experimental management program for the conservation of sensitive prey species: (1) determination of net rates of change of prey with declining population, (2) improvement of survivorship through habitat manipulation, (3) improvement of survivorship through predator removal, (4) determination of the threshold density above which reintroductions can succeed, and (5) manipulations to change interactions from Type II to Type III. The task in the future is to determine how to change the vulnerability of the prey so that they can have a refuge at low numbers. Predicción de los Efectos de la Depredación en la Conservación de una Presa en Peligro de Extinción En algunas partes del mundo como son las Islas del Pacífico, Australia y Nueva Zelandia, los veretebrados depredadores introducidos han ocasionado la desaparición de especies indígenas de mamíferos y aves. Un gran número de liberaciones para el restablecimiento de estas especies de mamíferos en tierras continentales de Australia han fracasado debido a que los depredadores han extirpado las poblaciones nuevas. La naturaleza de la declinación tanto de las poblaciones existentes como de las colonias reintroducidas provee información de las dinámicas de la depredación. La teoría sobre depredador‐presa sugiere que los efectos de la depredación son usualmente inversamente densodependientes (depensatorios) cuando las presas no son el alimento principal de los depredadores exóticos. Por lo tanto, estos depredadores pueden causar la extinción de especies de presas endémicas. Existen tres tipos de evidencia que pueden ser deducidas de las interacciones depredador‐presa y que permiten predicciones para la conservación: 1) que las tasas de cambio per cápita de presas incremente o disminuya con la declinación de las densidades de presas, 2) que la depredación sea depensatoria o densodependiente, y 3) la magnitude total de la depredación. Si la magnitud es muy alta para la coexistencia, entonces el grado de remoción del depredador requerido puede ser predecido. Si la magnitud de la depredación es suficientemente baja, entonces la densidad umbral de la presa que debe ser alcanzado mediante manejo y que permita al depredador y la presa coexistir tambien puede ser predecido. Analizamos reportes publicados tanto de declinaciones de poblaciones como de colonias reintroducidas de poblaciones de marsupiales en peligro de extinción en Australia. Las curvas de depredación observadas se conformaron a la teoría de depredador‐presa. Albunas (i.e. el ualaby, Petrogale lateralis ) fue una clasica presa alternativa y fue vulnerable por debajo del tamaño poblacional umbral. Otras (i.e. Bettongia penicillata ) tiene un refugio de números bajos y ofrece la mejor de las opciones para reintroducciones. Nuestras predicciones sugieren un protocolo para un programa de manejo experimental para la conservación de especies de presas sensitivas: 1) determinación de tasas netas de cambio de presa con población en declive, 2) mejora de la supervivencia mediante la manipualción del hábitat, 3) mejora en la supervivencia mediante remoción de depredadores, 4) determinación de la densidad umbral sobre la cual las reintroducciones podrían ser satisfactorias, y 5) manipulaciones para cambiar interacciones de tipo II y III. La tarea en el futuro será la de identificar el como cambiar la vulnerabilidad de la presa, de tal forma que puedan obtener refugio aún con números bajos.

The Effects of UV‐B Radiation on Toad Mortality in Mountainous Areas of Central Spain - Miguel Lizana; Emilio M. Pedraza (Conservation Biology, 1998)

Conflicts between Lesser Kestrel Conservation and European Agricultural Policies as Identif ied by Habitat Use Analyses - Jose L. Tella; Manuela G. Forero; Fernando Hiraldo; Jose A. Donazar (Conservation Biology, 1998)

An Informative Introduction - Leigh A. Davenport; Mark H. Waugh; Karl E. Miller; Campbell O. Webb; Jan Salick; Les Kaufman (Conservation Biology, 1998)

Effects of Solar UV-B Radiation on Embryonic Development in Hyla cadaverina, Hyla regilla, and Taricha torosa - Christopher R. Anzalone; Lee B. Kats; Malcolm S. Gordon (Conservation Biology, 1998)

Predicting Effects of Predation on Conservation of Endangered Prey - A. R. E. Sinclair; R. P. Pech; C. R. Dickman; D. Hik; P. Mahon; A. E. Newsome (Conservation Biology, 1998)

Conserving Dragonfly (Odonata) Assemblages Relative to River Dynamics in an African Savanna Game Reserve - David A. B. Stewart; Michael J. Samways (Conservation Biology, 1998)
Adult male dragonflies were sampled from 42 sites on four variously disturbed rivers and three reservoirs in Kruger National Park, South Africa. Fifty‐one species and 2671 individuals were recorded. Large flow fluctuations resulted in a high species turnover during sampling. Dragonfly species richness mostly conformed with the intermediate‐disturbance hypothesis, with species richness high on the rivers with moderate disturbance and low on the most disturbed ones. Ordination of dragonfly species data separated rivers into clear groups, indicating that the dragonfly assemblages reflected the distinct plant physiognomic and physical environmental conditions of each river system. Species that were abundant on any particular river had biotope preferences that reflected the overall environmental conditions of that river. Aquatic macrophytes, including two exotic invasive species, promoted dragonfly species richness. These species, however, were not rare or threatened. Highly disturbed rivers were characterized by species that preferred highly exposed situations with broad environmental conditions. In contrast, long grass or shady trees were important for some species because they buffered larger‐scale, unpredictable environmental changes. Biotic disturbance was also important because trampling by buffalo reduced local species richness and composition. Dragonfly assemblages were highly visible and sensitive indicators of aspects of long‐term environmental conditions of the water body. Management recommendations for dragonflies and other aquatic invertebrates include maintaining water and riparian biotope heterogeneity, maintaining constant flow rates and water levels, and allowing some macrophyte cover. A little natural and anthropogenic disturbance encourages much greater species richness than more extreme disturbance. The Sabie River is a major subject for conservation action in the premier protected area of Kruger National Park. Conservación de Ensamblajes de Libélulas (Odonata) Relativos a Dinámicas de Ríos en una Reserva Cinegética de una Sabana Africana Machos adultos de libélulas fueron muestreados en 42 sitios de quatro ríos perturbados de manera diversa y 3tres reservorios del Parque Nacional Kruger, Sudáfrica. Cincuenta y una especies y 2671 individuos fueron analizados. Fluctuaciones grandes del flujo resultaron en un cambio alto de especies durante el muestreo. La riqueza de especies de libélulas se conformó mayormente con la hipótesis de perturbación inmediata, con especies de alta riqueza en los rios con perturbación moderada y baja en los mas perturbados. La ordenación de datos de especies de libélulas separó a los ríos en grupos distintivos, indicando que los ensamblajes de libélulas reflejan las condiciones ambientales fisiognómicas y físicas de cada sistema fluvial. Las especies que fueron abundantes en algún río tuvieron preferencias de biotopo que reflejaron las condiciones ambientales generales de ese río en particular. Las macrofitas acuáticas, incluyendo dos especies invasivas exóticas, promovieron la riqueza de especies de libélulas. Estas especies, sin embargo, no fueron raras o amenazadas. Ríos altamente perturbados se caracterizaron por especies que prefirieron situaciones altamente expuestas con variedad de condiciones ambientales. En contraste, pastos altos o árboles de sombra fueron importantes para algunas especies debido a que amortiguaron cambios impredecibles de gran escala. La perturbacion biótica también fue un factor importante, puesto que el pisoteo de los bufalos redujo la riqueza y composición de las especies locales. Los ensamblajes de libélulas fueron indicadores altamente visibles y sensitivos de aspectos de condiciones ambientales de largo plazo del cuerpo de agua. Recomendaciones de manejo para libélulas y otros invertebrados acuáticos incluyen el mantenimiento de agua y la heterogeneidad del biotopo ripario, el mantenimiento del flujo constante y el nivel del agua y permitir la cobertura de macrofitas. Una pequeña perturbación natural y antropogénica promueve una riqueza de especies mucho mayor que una perturbación extrema. El rio Sabie es de gran importancia para acciones de conservación en el área protegida premier del Parque Nacional Kruger.

Letters - Alfred L. Gardner; Jerry T. Warren; Robert France (Conservation Biology, 1998)

Changes in Bird Abundance following Selective Logging on Seram, Indonesia - Stuart J. Marsden (Conservation Biology, 1998)
Timber concessions cover 90% of forest on some Indonesian islands, but the effects of logging on endemic‐rich island avifaunas are poorly known. I used a point count method to estimate population densities of Seram’s lowland birds in recently logged forest and in unlogged forest. Few bird species were excluded from logged forest, and several species were similarly common in the two habitats. Bird species diversity (the Shannon index) was, however, significantly lower in logged forest. The proportion of Seram’s species that declined after logging was comparable to that reported from species‐rich continental areas. There were also some similarities in the types of birds most affected. Species that were rare in unlogged forests were no more likely to decline after logging than were common ones. Although birds with small global ranges fared no worse than widespread species, several endemic forms were seriously affected. So many of the region’s taxa are endemic to single islands that logging concessions need to be examined at an individual island level and the presence or absence of endemic forms of susceptible genera considered. Cambios en la Abundancia de Aves Después de Tala Selectiva en Seram, Indonesia Cerca del 90% de los bosques en ciertas islas Indonesias están concesionados a compañías madereras, pero se conoce poco de los efectos de la tala sobre la avifauna rica en endemismos asociada a estas islas. Utilicé un método de conteo por puntos para estimar las densidades poblacionales de las aves de tierras bajas en Seram, en bosque talado recientemente y en bosque no talado. Pocas especies de aves fueron excluidas del bosque talado, y varias especies fueron similarmente comunes en los hábitats. Sin embargo, la diversidad de aves (mediante Índice de Shannon) fue significativamente menor en el bosque talado. La proporción de especies de Seram que declinaron después del talado fue comparable a la reportada para áreas continentales de alta riqueza de especies. También hubo similitud en el tipo de aves más afectadas. Las especies raras y comunes en bosques no talados tenían la misma posibilidad de declinar después del talado. Aunque las especies con pequeños rangos de distribución global no corrieron peor suerte que las especies de amplia distribución, hubo varias formas endémicas que fueron afectadas seriamente. Debido a que muchas taxa de la región son endémicas a una sola isla, las concesiones madereras deben ser examinadas a nivel individual, y se debe considerar la presencia o ausencia de formas endémicas.

An Interdisciplinary Tool for Monitoring Conservation Impacts in Madagascar - Claire Kremen; Isaia Raymond; Kate Lance (Conservation Biology, 1998)
Integrated conservation and development programs (ICDPs) are large, complex experiments in managing natural resources for both biodiversity and economic benefits. Monitoring should be an essential element within these programs to provide information for assessment and adaptive management; however, selecting appropriate indicators and designing effective monitoring programs is difficult due to their complexity. Useful native plants can make excellent indicator species for ICDPs because monitoring them provides information simultaneously on both ecological and socioeconomic change. In addition, monitoring useful species is necessary for establishing management plans for their sustainable use. On the Masoala Peninsula in Madagascar, site of an ICDP, we conducted household surveys and developed new ethnobotanical indices for selecting the most important plant species in different use categories from 105 forest products harvested destructively by local inhabitants. Unlike previous studies, use categories were defined non‐arbitrarily as groups of substitution products (e.g., products that are equivalent in their specific usage). By comparing use and preference within groups of substitution products, it is possible to predict over‐extraction of preferred species and resource switching to secondary species. Knowledge of substitution groups is thus a necessary prerequisite for selecting indicator species that will furnish early warnings of non‐sustainable use. We identified 13 groups of substitution products covering the major household uses on Masoala. From these we selected the 25 species that were most heavily used or preferred. Following the use of these species over time will permit a detailed spatial and temporal analysis of changes in resource use patterns and harvesting impacts in response to the integrated conservation and development program, ultimately allowing the test of the hypothesis that economic development linked to conservation promotes conservation. Una herramienta Interdisciplinaria para Monitorear Impactos de la Conservación en Madagascar Los programas integrales de conservación y desarrollo (PICD) son experimentos grandes y complejos para manejar los recursos naturales para beneficios tanto conservacionistas como económicos. El monitoreo es un elemento esencial dentro de estos programas ya que proporciona información para la evaluación y el manejo adaptivo; sin embargo, la selección de indicadores adecuados y el diseño de programas efectivos de monitores es difícil debido a su complejidad. Las plantas nativas útiles son un excelentes especies indicadoras para los PICD, porque al monitorearlas se obtiene información ecológica y socioeconómica simultáneamente. Adicionalmente, el monitoreo de especies útiles es necesario para el establecimiento de planes de manejo para su uso sustentable. En la Península Masoala de Madagascar, sitio de un PICD, aplicamos encuestas domésticas y desarrollamos nuevos índices etnobotánicos para seleccionar a las especies de plantas más importantes, en diferentes categorías de uso, de 105 productos forestales cosechados destructivamente por habitantes locales. A diferencia de estudios previos, las categorías de uso fueron definidas no arbitrariamente como grupos de productos de sustitución (e.g., productos equivalentes en su uso específico). Comparando uso y preferencia entre grupos de productos de sustitución, es posible predecir la sobre‐cosecha de especies preferidas y el cambio de recursos a especies secundarias. Por consiguiente, el conocimiento de los grupos de sustitución es un prerequisito necesario para seleccionar especies indicadoras que darán señales de uso no sustentable. Identificamos 13 grupos de productos de sustitución que abarcan los principales usos domésticos en Masaola: de ellos seleccionamos las 25 especies más utilizadas o preferidas. El seguimiento del uso de estas especies en el tiempo permitirá tener un detallado análisis espacial y temporal de cambios en los patrones de utilización de recursos e impactos cosecha como respuesta al programa integral de conservación y desarrollo, pudiendo con ello probar la hipótesis de que el desarrollo económico ligado a la conservación promueve la conservación.

Effectiveness of a Vegetation-Based Approach to Insect Conservation - Ron Panzer; Mark W. Schwartz (Conservation Biology, 1998)

High Dams and Marine‐Freshwater Linkages: Effects on Native and Introduced Fauna in the Caribbean - Jeff G. Holmquist; Jutta M. Schmidt‐Gengenbach; Beverly Buchanan Yoshioka (Conservation Biology, 1998)
Caribbean streams are dominated by a shrimp and fish assemblage for which amphidromy (eggs or larvae carried to the ocean followed by migration of juveniles upriver) is suspected. Effects of dams on this assemblage are likely to demonstrate complex interactions as a function of reproductive strategy and type of dam structure. Our goals were to determine (1) whether high dams reduce or eliminate stream corridor permeability with respect to migration, (2) the extent to which permeability is a function of spillway discharge, (3) the relative roles of native fauna and disturbance suppression (in this case, river regulation) as predictors of success by exotic fishes, and (4) the uniformity and extent of obligate amphidromy in this assemblage. We sampled adults and juveniles of shrimps and fishes in Puerto Rican streams via electrofishing and sampled shrimp larvae with drift nets. Replicate stream reaches were assigned to the following five categories: undammed, above or below dams, and with or without water released over spillways. Dams without such discharge were impermeable barriers that eliminated all native fish and shrimp fauna from upstream reaches. Though more permeable, dams with spillway discharge had smaller populations of native species above these structures than below the dams or on undammed streams. Our data on adult and larval distributions, combined with the absence of first‐stage shrimp larvae, indicate that amphidromy is obligate for most of the native fauna. Disturbance regime appeared to be a poor predictor of successful invasion by exotics in this system, whereas exotic abundance was consistently inversely related to abundance and species richness of native fauna across all sampling categories. The prevalent amphidromy in these streams provides a tight marine‐upland linkage that is disrupted by dams in several ways. We recommend adding shrimp and fishways to dams on these tropical streams. Efectos de Reservorios de Agua Elevados y Conexiones Marino‐Agua Dulce en la Fauna Nativa e Introducida del Caribe Los ríos del Caribe están dominados por una comunidad compleja de camarones y peces los cuáles se sospecha que la gran mayoría son anfidromos (los huevos y larvas regresan al mar antes de que los juveniles migren río arriba). Es probable que los efectos de las represas de agua se expresen como interacciones complicadas entre el diseño de las estructuras y las estrategias reproductivas de estos animales. Nuestras metas fueron las de determinar: (1) si las represas elevadas reducen o eliminan la permeabilidad del río con respecto a la migración de este complejo de animales, (2) hasta donde el tipo de permeabilidad es una función de la descarga por el derramadero, (3) los roles relativos de la fauna nativa y la supresión por perturbación como pronosticadores del éxito de las especies de peces exóticas, y (4) la uniformidad y la extensión de la anfidromía obligada en este complejo de organismos. Se colectaron muestras en algunos ríos en Puerto Rico usando técnicas de equipo de electropesca y redes de plancton. Se tomaron réplicas en ríos similares o ramales de ríos que fueron asignados a las siguientes categorías: sin represa u obstrucción, río arriba y río abajo de las represas con o sin descarga por encima de la represa. Represas sin descarga por encima constituyen obstáculos impermeables que eliminaron los peces y camarones nativos de arriba de las presas. Las represas con descarga encima, aunque eran más permeable, redujeron significativamente las poblaciones de camarones y peces río arriba de las estructuras. Los datos de distribuciones de adultos y larvas, considerando particularmente que solamente encontramos larvas de camarones de la primera etapa, indican que la vida anfidroma es obligada para los peces y camarones nativos. Parece que el régimen de perturbación no es un buen pronosticador de la habilidad de invasión de los peces exóticos, considerando que su abundancia era inversamente proporcional a la abundancia de especies nativas en todas las categoría de ríos muestreados. La prevalencia de anfidromos en estos ríos indica un enlace fuerte entre el mar y los sitios río arriba que puede ser perturbada por la construcción de represas o varias escalas de consideración. Nosotros recomendamos la siembra de peces y camarones en las represas construidas en estos ríos tropicales.

Spatial Autocorrelation in California Land Birds - Walter D. Koenig (Conservation Biology, 1998)
Asynchrony in recruitment and survivorship in populations located within the potential range of dispersal generally facilitates metapopulation processes’ playing an important role in the demographic “rescue” of populations. Conversely, populations that are demographically synchronous over large geographic areas may be particularly vulnerable to the detrimental effects of habitat fragmentation because such synchrony is probably maintained largely by dispersal. To examine the potential generality of such processes, I investigated spatial autocorrelation in annual relative density of California land birds using data from the Breeding Bird Survey and the Christmas Bird Count. Of 88 species I examined using Breeding Bird Survey data, 87 (99%) exhibited no significant spatial autocorrelation at any distance category. Of 79 species I examined using Christmas Bird Count data, 66% exhibited no significant spatial autocorrelation. These results suggest that demographic processes are often asynchronous over relatively short geographical distances and thus that metapopulation processes may be significant for a large fraction of terrestrial bird species. No species during the breeding season, but a small proportion during the winter, were significantly spatially autocorrelated at all geographic scales up to the statewide level (500–1200 km). There was no significant relationship between spatial autocorrelation during the winter and either body size, clutch size, or diet, but migratory species were more spatially autocorrelated than resident species. Spatial autocorrelation in the winter was also related to breeding habitat preferences, with species inhabiting savanna and woodlands (especially oak woodlands) exhibiting lower spatial autocorrelation and those inhabiting subalpine forest exhibiting greater spatial autocorrelation than other species. Autocorrelación Espacial en Aves Terrestres de California La asincronia en el recrutamiento y supervivencia de poblaciones localizadas dentro del rango potencial de disperción, generalmente facilita procesos metapoblacionales que juegan un papel importante en el “rescate” demográfico de poblaciones. Contrariamente, poblaciones que son demográficamente sincrónicas en áreas geográficas extensas pudieran ser particularmente vulnerables a los efectos negativos de la fragmentación del hábitat, debido a que dicha sincronia es probablemente mantenida por la dispersión. Para examinar la generalidad potencial de este proceso, investigué la autocorrelación espacial en densidades anuales relativas de aves terrestres de California mediante el uso de muestreos de aves anidando y datos de conteos de aves en navidad. De las 88 especies examinadas utilizando muestreos de aves anidando, 87 (99%) no exhibieron autocorrelación espacial significativa para ninguna categoria de distancia. De 79 especies examinadas con conteos de aves en navidad, 66% no exhibió autocorrelación espacial significativa. Estos resultados sugieren que los procesos demográficos son frecuentemente asincrónicos dentro de distancias geográficas relativamente cortas y es por ello que los procesos metapoblacionales pueden ser significativos para una fracción de especies de aves terrestres. Durante la temporada de reproducción, ninguna especie estuvo autocorrelacionada espacialmente, sin embargo una poporción pepueña estuvo autocorrelacionada espacialmente durante el invierno a todas las escalas geográficas, incluyendo el nivel de rango estatal (500–1200 km). No existió relación significativa entre autocorrelación espacial durante el verano y el tamaño del cuerpo, el tamaño de nidada o la dieta; sin embargo, las especies migratorias estuvieron mas autocorrelacionadas que las especies residentes. La autocorrelación espacial en el verano estuvo también relacionada con las preferencias en hábitat para reproducción, con especies habitando la sabana y los bosques de madera (especialmente los de encino) que exhibieron menor autocorrelación espacial y aquellas especies habitantes de bosques subalpinos que exhibieron mayor autocorrelación espacial que las otras especies.

The Impact of Individual Tree Harvesting on Thermal Environments of Lizards in Amazonian Rain Forest - Laurie J. Vitt; Teresa C. S. Avila-Pires; Janalee P. Caldwell; Veronica R. L. Oliveira (Conservation Biology, 1998)

Wood Thrush Population Sinks and Implications for the Scale of Regional Conservation Strategies - Cheryl L. Trine (Conservation Biology, 1998)
I measured the season‐long nesting productivity of 60 pairs of color‐banded Wood Thrushes ( Hylocichla mustelina ) in three of the largest forest tracts (1100–2200 ha) in southern Illinois (U.S.A.) in the Shawnee National Forest from 1990 to 1992. The purpose was to determine if these tracts are likely population sources—if they produce a surplus of young that would be available to colonize hypothesized population sinks in smaller, more fragmented tracts where productivity is unlikely to be sufficient to compensate for mortality. Levels of parasitism by Brown‐headed Cowbirds ( Molothrus ater ) were high (75–95% of nests were parasitized; 2.0–2.7 cowbird eggs/parasitized nest), as were nest predation rates (typically 50–80% of the nests failed). In spite of the Wood Thrush’s capacity to raise two or three broods a season and raise mixed broods of hosts and cowbirds, nesting productivity was low (0.3–2.1 fledglings/female/year). Using a range of estimates for adult and juvenile survival, I estimated that populations in all three sites were population sinks in most years. Cowbird parasitism and nest predation contributed roughly equally to the low productivity; some sites would have been sinks even without parasitism, whereas other sites would continue to be sinks even with substantially reduced nest predation rates when cowbird parasitism levels remain unchanged. Maintaining Wood Thrush populations in the U.S. Midwest might require much larger (>2500 ha) reserves than populations in the East, where even a small woodlot ( Sumideros Poblacionales de Hylocichla mustelina y sus Implicaciones en Estrategias de Conservación a Escala Regional Realicé mediciones de la productividad en la estación prolongada de anidamiento de 60 pares de Hylocichla mustelina en tres de las mas grandes áreas boscosas (1100–2200 ha) del sur de Illinois (U.S.A.) del Bosque Nacional Shawnee antre 1990–1992. El propósito de este estudio fue determinar si estas extensiones son fuentes poblacionales (i.e. para producir un abastecimiento de jovenes que podría ser viable para colonizar sumideros poblacionales hipotéticos en territorios mas pequeños, mas fragmentados, donde la productividad no es suficiente para compensar la mortalidad). Los niveles de parasitismo por Molothrus ater fueron altos (75–95% de los nidos parasitados; 2.0–2.7 huevos/nido parasitado), lo mismo que las tasas de depredación (tipicamente 50–80% de los nidos fracasaron). A pesar de que Hylocichla mustelina tiene la capacidad para tener dos o tres grupos de crias por estación y engordar grupos mixtos de polluelos propios y parásitos, la productividad de anidación fue baja (0.3–2.1 polluelos/hembra/año). Utilizando tasas de estimación de la supervivencia de juveniles y adultos, determiné que las poblaciones en los tres sitios son sumideros poblacionales en casi todos los años. El parasitismo de Molothrus ater y la depredación contribuyeron casi de la misma manera a la baja productividad; algunos sitios podrían ser sumideros poblacionales aún sin parasitismo, mientras que otros sitios podrían continuar como sumideros aún con una reducción substancial de las tasas de depredación de nidos donde el parasitismo se se mantenga constante. El mantenimiento de poblaciones de Hylocichla mustelina en la zona del medio oeste de los Estados Unidos podría requerir de reservas mucho mas grandes (>2500 ha) que las poblaciones del este donde áreas pequeñas de madera (

Natural Variation in Horn Size and Social Dominance and Their Importance to the Conservation of Black Rhinoceros - Joel Berger; Carol Cunningham (Conservation Biology, 1998)

Factors Influencing the Dynamics of Occurrence of the Hazel Grouse in a Fine‐Grained Managed Landscape - Lennart Saari; Johan Åberg; Jon E. Swenson (Conservation Biology, 1998)
The objective of this study was to test whether the pattern and dynamics of occurrence of Hazel Grouse ( Bonasa bonasia ) in a fine‐grained landscape mosaic could be predicted from the results of a study in a more intensively managed coarse‐grained landscape with much less suitable habitat and a different matrix. Twenty‐one years of regular inventories of Hazel Grouse during spring, summer, and autumn and a vegetation map of suitable Hazel Grouse habitat were used to analyze the extinction and (re)colonization of Hazel Grouse in different patches in relation to the size and isolation of the patch and the vegetation surrounding it. As predicted, patch area was the most important variable determining Hazel Grouse occupancy, (re)colonization, and local extinction. Also as predicted, the proportion of open habitat surrounding the habitat (i.e., an isolation effect) was also important. The isolation effect occurred at a smaller scale in the fine‐grained habitat than the intensively managed landscape. This was apparently related to the type of matrix: open land in the fine‐grained landscape and unsuitable, but forested, habitat in the coarse‐grained landscape. The Hazel Grouse appears to be unusually sensitive to habitat fragmentation, but the mechanism causing the isolation effect differed between landscapes, probably because of the amount of suitable habitat left and the type of matrix in the landscape. Factores que Influyen en la Dinámica de Distribución del Grévol en un Paisaje Manejado y Finamente Fragmentado El objetivo de este estudio fue determinar si el patrón y la dinámica de distribución del grévol ( Bonasa bonasia ) en un paisaje fragmentado de grano fino pueden ser predichos a partir de los resultados de un estudio realizado en un paisaje de grano grueso con mucho menos hábitat adecuado, con una matriz distinta y manejado intensivamente. Utilizamos datos de veintiún años de inventarios regulares de grévol en primavera, verano y otoño, así como un mapa de vegetación de hábitat adecuado para la especie, para analizar la extinción y (re)colonización del grévol en diferentes parches de hábitat en relación con el tamaño y aislamiento del parche y la vegetación circundante. Tal como se predijo, el tamaño del parche de hábitat adecuado fue la variable más importante para determinar la distribución, la (re)colonización y la extinción local del grévol. Además, como se predijo, la proporción de hábitat abierto alrededor del parche de hábitat (i.e., un efecto del aislamiento) también fue importante. El efecto de aislamiento ocurrió a menor escala en el hábitat de grano fino que en el paisaje manejado intensivamente. Aparentemente, esto estaba relacionado con el tipo de matriz: área abierta en el paisaje de grano fino y hábitat boscoso, pero inadecuado, en el paisaje de grano grueso. El grévol parece ser inusualmente sensible a la fragmentación del hábitat, pero el mecanismo que causa el efecto de aislamiento fue distinto en los dos paisajes, probablemente debido a la cantidad de hábitat adecuado y al tipo de matriz en el paisaje.

Inbreeding and Extinction: Island Populations - Richard Frankham (Conservation Biology, 1998)
Island populations are more prone to extinction than mainland populations, with island endemic species having higher extinction rates than nonendemic species. Inbreeding depression is one possible explanation for this. Insular populations are expected to suffer increased inbreeding relative to mainland populations due to bottlenecks at foundation and to lower subsequent population sizes. Inbreeding coefficients for 182 nonendemic and 28 endemic island populations were estimated from allozyme and microsatellite heterozygosities in island and related mainland populations. Island populations were significantly inbred, with inbreeding coefficients significantly higher in endemic than nonendemic island populations. Many island populations showed levels of inbreeding associated with elevated extinction rates in domestic and laboratory species. Inbreeding depression cannot be excluded as a factor in the extinction proneness of island populations. Intracruza y Extinción: Poblaciones Isleñas Poblaciones Isleñas presentan una mayor tendencia a la extinció que las poblaciones continentales, teniendo las especies endémicas una mayor tasa de extinción que las especies no endémicas. La depresión por intracruza es una explicación posible a esto. Es de esperarse que poblaciones insulares sufran una intracruza relativemente mas alta que las poblaciones continentales debido a cuellos de botella a nivel de tamaño poblacional de fundación y subsecuentes tamaños poblacionales menores. Los coeficientes de intracruza para 182 poblaciones no endémicas y 28 poblaciones endémicas se estimaron mediante heterozigocidades de alozimas y microsatélites de poblaciones de islas y especies continentales relacionadas. Las poblaciones isleñas estuvieron significativamente intracruzadas, con coeficientes de intracruza signifiativamente mayores en poblaciones endémicas que en las poblaciones no endémicas. Muchas poblaciones isleñas mostraron niveles de intracruza asocidos con elevadas tasas de extinción en especies domesticas y de laboratorio. La depresión por intracruza no puede ser excluída como un factor en la tendencia a la extinción de especies isleñas.

Wood Thrush Population Sinks and Implications for the Scale of Regional Conservation Strategies - Cheryl L. Trine (Conservation Biology, 1998)

Critical Biodiversity - J. H. Kaufman; D. Brodbeck; O. R. Melroy (Conservation Biology, 1998)

Livestock Grazing and Biodiversity Conservation: Comments on Saberwal - Charudutt Mishra; G. S. Rawat (Conservation Biology, 1998)

Geographic Isolation of Hector’s Dolphin Populations Described by Mitochondrial DNA Sequences - F. B. Pichler; S. M. Dawson; E. Slooten; C. S. Baker (Conservation Biology, 1998)
To describe the genetic structure of Hector’s dolphin ( Cephalorhynchus hectori ) populations, we used the polymerase chain reaction to amplify and sequence a 360 base‐pair fragment of the mitochondrial DNA control region from 34 beachcast or gillnet‐caught specimens. Variation in these sequences identified 11 distinct haplotypes differing from one another by 0.28–1.67% and by an average of 4.47% from the closely related Commerson’s dolphin. The genealogical relationship of these haplotypes showed a strong concordance with the geographic origins of the samples. An analysis of variance modified for molecular data showed that 74% of the sequence variation could be explained by the three primary sampling regions: the North Island, the west coast of the South Island, and the east coast of the South Island. Such a marked segregation of maternal lineages across a small geographic range is unusual among cetaceans. The low rate of female dispersal, as indicated by this mitochondrial DNA structure, could increase the vulnerability of local populations to extinction due to fisheries‐related mortality. Aislamiento Geográfico de Poblaciones del Delfin de Hector Descritas por Secuencias Mitocondriales de ADN Para describir la estructura genética del delfín de Hector ( Cephalorhynchus hectori ), utilizamos la reacción de polimerasa en cadena para amplificar y secuenciar un fragmento de la región control del ADN‐mitocondrial de 360 pares de bases provenientes de 34 especímenes varados en playas o capturados en redes agalleras. La variación de las secuencias identificaron 11 haplotipos distintivos difiriendo entre ellos por un 0.28–1.67% y por un promedio de 4.47% del relativamente cercano delfin de Commerson. La relación genealógica de estos haplotipos muestran una fuerte concordancia con los origenes geográficos de las muestras. Un análisis de varianza modificado para datos moleculares mostró que 74% de la variación de las secuencias puede ser explicada por tres regiones de muestreo primarias: la isla del norte, la costa oeste de la isla del sur y la costa este de la isla del sur. Esta segregación tan marcada de linajes maternales a lo largo de un rango geográfico pequeño es inusual en cetáceos. La baja tasa de dispersión de hembras, indicada por la estructura del DNA mitocondrial, podría incrementar la vulnerabilidad de las poblaciones locales a la extinción debido a la mortalidad relacionada con pesquerías.

Structural Characteristics of Old- and Second-Growth Stands of Longleaf Pine (Pinus palustris) in the Gulf Coastal Region of the U.S.A. - Jill M. Noel; William J. Platt; E. Barry Moser (Conservation Biology, 1998)

Degradation and Environmental Conservation: Response to Mishra and Rawat - Vasant K. Saberwal (Conservation Biology, 1998)

The Global 200: A Representation Approach to Conserving the Earth’s Most Biologically Valuable Ecoregions - David M. Olson; Eric Dinerstein (Conservation Biology, 1998)

Tidal currents, mean flows, and upwelling on the north‐east shelf of New Zealand - Jonathan Sharples; Malcolm J. N. Greig (New Zealand Journal of Marine and Freshwater Research, 1998)
Continuous time‐series of near‐bed and near‐surface currents and temperature were recorded, at the shelf edge and on the shelf of northeast New Zealand, between June 1994 and January 1996. Tidal analysis of the current records show that typical tidal currents in the region are dominated by the Mj constituent, with amplitudes between 5 and 10 cm s ‐1 . The amplitude of the M 2 tide varies in response to the existence of an internal tide, and the tide was also found to include higher harmonics of the M 2 tide during periods of strong internal tide activity. These higher harmonics are likely to be the result of a non‐linear internal tide. Mean flows at the surface throughout the records were generally parallel to the bathymetry and towards the southeast, with typical speeds of between 20 and 30 cm s ‐1 , sometimes reaching 60 cm s ‐1 near Cape Brett. It is suggested that flow curvature around Cape Brett could be a significant localised upwelling mechanism. Near‐bed currents showed a strong cross‐shelf component in response to along‐shelf wind stress, indicating episodic wind‐driven upwelling events driving slope water onto the shelf between the autumnal and vernal equinoxes. It is estimated that such upwelling introduces a net supply of 10 ± 3 mmol m ‐3 of nitrate to the shelf waters between Cape Brett and Hauraki Gulf.

Coherent signals in the temperature and height of the sea surface off North Cape, New Zealand - Andrew K. Laing; Niles A. Oien; Richard Murphy; Michael J. Uddstrom (New Zealand Journal of Marine and Freshwater Research, 1998)
Dynamic heights of the ocean surface to the north‐east of North Cape, New Zealand are determined from 18 months of Topex‐Poseidon altimeter measurements along a repeat track crossing the East Auckland current system. The anomalies in the heights and in the cross‐track geostrophic currents derived from these heights both portray strong cyclic signals with period of c. 140 days travelling towards New Zealand, and a signal with period of at least 18 months in the opposite sense. Sea‐surface temperature (SST) anomalies and anomalies in the along‐track SST gradients exhibit similar periodicity. The coherence between anomalies in velocity and temperature gradient and that between anomalies in height and temperature both reach c. 0.74 at the period of 140 days and 0.88 for the long‐period signal. A correspondence is also shown between the positions of maximum flow in the East Auckland current and positions of high sea‐surface temperature gradient. Winds are shown to affect the strength of the 140‐day signal in the temperature gradient data, and to impair its coherence with the matching signal in the velocity anomaly data. In particular, if temperature gradient data are smoothed through times and places where the recent history of the curl of the wind‐stress is significantly positive (Ekman pumping occurring) the coherence in the 140‐day signal between the velocity and temperature gradient is increased from 0.74 to 0.92. Similar impacts on the longer period signal are not found, nor are they evident for either of the two prominent signals in the coherence between SST and height anomalies.

210 Pb chronology from Wellington Harbour, New Zealand - James R. Goff; Neil E. Whitehead; Robert G. Ditchburn (New Zealand Journal of Marine and Freshwater Research, 1998)
A sediment accumulation record based on the levels of “unsupported” 210 Pb was obtained from a core taken from the centre of Wellington Harbour, New Zealand. Sediment accumulation rates (SARs) varied from 3 to 5 mm yr ‐1 . Before 1920, SARs were sufficiently high to dilute unsupported levels of 210 Pb to background, but had fallen below the mean by 1925 maintaining constant SARs until 1953. These data provide a higher resolution chronology of early 20th century SARs than was previously available. Comparison with 137 Cs data confirms that there was a significant increase in SARs between 1953 and 1967, but that these have remained fairly constant since 1974. Data from the two radionuclides are consistent after 1974, and 210 Pb data are consistent with other chronological measurements before 1953. Therefore, it is suggested that the two radionuclides are immobile in the marine sediments of Wellington Harbour and that differences between the two SARs are real.

Macroinvertebrate distribution in the littoral zone of Lake Coleridge, South Island, New Zealand—effects of habitat stability, wind exposure, and macrophytes - M. R. James; M. Weatherhead; C. Stanger; E. Graynoth (New Zealand Journal of Marine and Freshwater Research, 1998)
The macroinvertebrate community was surveyed at eight littoral zone sites in Lake Coleridge, New Zealand. Sites covered a range of conditions including exposure to prevailing winds, shore‐line topography, and proximity to river inputs—which are a major source of suspended sediment to the lake. The littoral zone contained an abundant and diverse macroinvertebrate fauna (47 taxa). Three communities were identified: a shallow‐water community inhabiting the wave‐break zone, dominated by Trichoptera and chironomid larvae; a middle‐zone community associated with macrophyte beds, with high macroinvertebrate abundance and dominated by gastropods and oligochaetes; and a community in fine sediments below the macrophytes dominated by oligochaetes. The depth distribution of these communities was related to substrate, macrophyte abundance, and shore‐line profile. Superimposed on this pattern were the effects of hillside slope and exposure to prevailing north‐west winds. Greatest abundance was associated with macrophytes on stable shores at 4–7.5 m depth, i.e., below the effective wavebase depth. Sediment deposition had only a localised direct effect close to where river water enters the lake. Indirect effects were mediated through the effects of suspended solids on water clarity, bottom limits, and production of macrophytes and periphyton. Estimates of the proportion of littoral macroinvertebrate biomass to whole‐lake zooplankton biomass was 10:1 and for production was 1.3:1, indicating the potential importance of the littoral zone to whole‐lake production.

Factors associated with the distribution and habitat of eels ( Anguilla spp.) in three New Zealand lowland streams - G. J. Glova; D. J. Jellyman; M. L. Bonnett (New Zealand Journal of Marine and Freshwater Research, 1998)
The distributions of shortfinned eels ( Anguilla australis ) and longfinned eels ( A. dieffenbachii ) of all sizes in three New Zealand coastal streams were investigated during summer by sampling stratified, randomly chosen pool, run, and riffle sites from tidal to upper reaches. In all streams, both species were widespread, although a greater proportion of the total population of shortfinned eels was present in the lower reaches and small eels ( ‐2 ) of longfinned eels ‐2 ) for four size groups (

Comparison of fish communities and abundance in unmodified streams of Kahurangi National Park with other areas of New Zealand - I. G. Jowett; J. W. Hayes; N. Deans; G. A. Eldon (New Zealand Journal of Marine and Freshwater Research, 1998)
New Zealand landscapes were extensively modified after European settlement in the late 1800s. Large areas of native forest were converted to pasture and few large areas of unmodified forest remain. Trout ( Salmo trutta and Oncorhynchus mykiss ) were introduced into the rivers at the same time, and these two changes are thought to have affected native fish communities. Kahurangi National Park is a large area of unmodified native forest with few introduced trout in smaller rivers draining to the west. A survey of these streams was made to determine whether their communities differed from those in other areas of New Zealand. No non‐diadromous native fish were found, suggesting a biogeographic separation from adjacent eastern and southern areas since the Pliocene or early Pleistocene. Contrary to popular expectation, fish diversity and abundance was often lower than at equivalent elevations in other areas of New Zealand. Lowland fish communities comprised a small stream community dominated by inanga ( Galaxias maculatus ), a small stream community containing a mixed galaxiid population but dominated by banded kokopu ( Galaxias fasciatus ), and two large stream communities containing the fastwater species bluegilled bully ( Gobiomorphus hubbsi ), and dominated by either redfinned bully ( Gobiomorphus huttoni ) or bluegilled bully. Large streams usually contained no in‐stream cover with margins of exposed streambed, whereas small streams contained plentiful cover with margins of native forest, native grasses, or swamp. Upland fish communities were dominated by koaro ( Galaxias brevipinnis ) and/or longfinned eels ( Anguilla dieffenbachii ). Large‐stream fish communities in Kahurangi National Park were similar to the fastwater communities in medium‐large rivers in other areas of New Zealand. However, in the smaller streams of Kahurangi National Park, galaxiid communities were encountered more frequently than in similar sized streams in other parts of New Zealand.

Distribution of seabirds in coastal waters off Otago, New Zealand - Richard L. O'Driscoll; Martin Renner; Frank J. Austin; Hamish G. Spencer (New Zealand Journal of Marine and Freshwater Research, 1998)
The occurrence, abundance, and distribution of seabirds was studied in a physically dynamic region off the coast of Otago, New Zealand. Eleven line‐transect surveys were conducted in late summer and autumn of 1994–96, when surface swarms of “krill”, Nyctiphanes australis , were present in the study area. Twenty species of seabird were recorded. The abundance and occurrence of species varied between sitting and flying counts. The most numerous species were sooty shearwaters ( Puffinus griseus ), red‐billed gulls ( Larus novaehollandiae ), black‐billed gulls ( L. bulleri ), and black‐backed gulls ( L. dominicanus ). Most species were recorded throughout the study area, and different species were commonly observed together. Spatial similarity matrices revealed strongest association between red‐ and black‐billed gulls and black‐backed gulls. The small (kilometre) scale distribution of seabirds varied between surveys, between transects, and between repeated runs of the same transect 1–3 h apart. Correlations between seabird abundance, salinity gradient, and krill density were weak. Counts of seabirds were highly positively skewed. This skewness, together with spatial and temporal variability in the distribution of flocks, would make abundance estimation at sea difficult.

Retention and in situ detectability of visible implant fluorescent elastomer (VIFE) tags in Pagrus auratus (Sparidae) - Trevor J. Willis; Russ C. Babcock (New Zealand Journal of Marine and Freshwater Research, 1998)
This paper assesses the potential effectiveness of the visible implant fluorescent elastomer (VIFE) tagging system for identifying groups of snapper ( Pagrus auratus: Sparidae) in the field. Retention rate after surface tagging longline‐caught fish was 93% over a 2‐week period, with no mortality attributable to tagging. Incidence of fin or scale infection did not differ between tagged and control fish. A protocol for tagging snapper underwater was also developed. This technique caused less stress to the fish than remote fishing methods, but was labour intensive when large sample sizes were required. Orange VIFE tags were visible to divers at ranges of up to 6 m in water visibility of 8–10 m, when exposed to light frequencies capable of inducing fluorescent emissions. Red, green, and yellow tags were only identifiable at shorter ranges, depending on ambient light levels and direction. The range of tag detection increased with increasing water clarity. We suggest that VIFE tagging has better retention rates and is less intrusive compared with previously employed externally readable tags. Because tags are identifiable in situ without the necessity of recapture, this method has potentially wide‐ranging applications in fish ecology and behavioural studies for adult as well as juvenile fishes.

Iso‐electric focusing and the identification of fisheries’ waste in the diet of Westland petrels ( Procellaria westlandica ) - Amanda N. D. Freeman; Peter J. Smith (New Zealand Journal of Marine and Freshwater Research, 1998)
Iso‐electric focusing was used to identify fish tissue in Westland petrel ( Procellaria westlandica ) diet samples. Forty‐five percent of the samples from Westland petrel stomachs produced clear protein banding patterns and more than half of these were identified as species common in fisheries’ waste. Proteins in the other samples were presumably too digested for this technique. Iso‐electric focusing is a comparatively quick and inexpensive technique and is particularly useful for diet studies where flesh eaten is likely to be relatively undigested at the time of sampling.

Characterising food‐webs in two New Zealand streams - N. G. Jaarsma; S. M. de Boer; C. R. Townsend; R. M. Thompson; E. D. Edwards (New Zealand Journal of Marine and Freshwater Research, 1998)
The food‐web communities of two stony tributaries of the Taieri River in New Zealand were documented. We placed heavy emphasis on algal and macroinvertebrate taxonomy, identifying most taxa to species or morpho‐species level. Food‐web attributes were derived from symmetrical matrices using an Excel macro. The values of the food‐web attributes are generally consistent with generalities that have previously been reported in food‐web studies, although some hypothesisied relationships between connectance and food‐web size did not hold. The patterns detected were robust to the inclusion or exclusion of species that were identified in gut contents but not in field samples. The attributes strongly reflected the trophic status of the streams. Dempsters Creek was classified as autotrophic (based on high primary production and a high ratio of production to respiration) and displayed a larger food‐web size and longer food‐chains than those seen in Healy Creek, which was classified as hetero‐trophic (lower primary production and production to respiration ratio). The importance of dynamic environmental attributes such as production and disturbance in structuring food‐webs is emphasised in this study.

Sharks and rays of New Zealand. By GeoffreyCox and MalcolmFrancis. Published in 1997 by Canterbury University Press, University of Canterbury, Private Bag 4800, Christchurch, New Zealand. 68 p. ISBN: 0–908812–60–4. Price: NZ$29.95. - Clive D. Roberts (New Zealand Journal of Marine and Freshwater Research, 1998)

Allozyme and mitochondrial DNA variation in three species of oreos (Teleostei: Oreosomatidae) from Australasian waters - R. D. Ward; N.G. Elliott; P. M. Grewe; P. R. Last; P. S. Lowry; B. H. Innes; G. K. Yearsley (New Zealand Journal of Marine and Freshwater Research, 1998)
Collections of three species of oreos (smooth oreo, Pseudocyttus maculatus; black oreo, Allocyttus niger; and warty oreo, A. verrucosus ) from Australasian waters were examined for genetic variation. Allozyme heterozygosity was high in each species (25–29 loci: mean heterozygosity per locus per sample ranging from 0.100 to 0.148), but mitochondrial DNA variation was less extensive (10 six‐base restriction enzymes: nucleotide diversity ranging from 0.0012 to 0.0021). Collections of smooth oreos from Western Australia, Tasmania, and New Zealand did not permit the null hypothesis of a single stock to be confidently rejected. Black oreos from Tasmania and New Zealand were provisionally identified as separate stocks. Warty oreos from Tasmania were provisionally identified as separate from a Western Australia/New South Wales stock.

Distinguishing human from animal faecal contamination in water: A review - L. W. Sinton; R. K. Finlay; D. J. Hannah (New Zealand Journal of Marine and Freshwater Research, 1998)
Management of faecal contamination of water would be improved if sources could be accurately identified through water analysis. Human faeces are generally perceived as constituting a greater human health risk than animal faeces, but reliable epidemiological evidence is lacking. United States waterborne disease data suggest that human‐specific enteric viruses account for over half the documented outbreaks. However, in New Zealand, where there is a high grazing animal:human ratio (increasing the relative importance of water‐transmissible zoonoses), it seems prudent to assume that human and animal faecal pollution both constitute a risk to human health. Irrespective of the relative risks, the ability to identify sources would assist in overall management of microbial water quality. Faecal streptococci do not appear to provide reliable faecal source identification. Human and animal sources, respectively, maybe distinguishable by two tests on Bifidobacterium spp.—growth at 45°C in trypticase phytone yeast broth and sorbitol fermentation. Different species of Bacteroides tend to be present in humans and animals, but poor survival in water is a problem. Phages of the Bacteroides fragilis strain HSP40 appear to be human specific, but low counts in effluent in some countries, including New Zealand, may limit their usefulness. Different F‐RNA phage subgroups appear to be associated with human and animal faecal sources. The actinomycete Rhodococcus coprophilus has potential as a grazing animal indicator but it is persistent, and existing culturing techniques are time consuming. The development of DNA‐based techniques, such as polymerase chain reaction (PCR), may assist in the assay of some microbial faecal source indicators. Various faecal sterol isomers offer the possibility of distinguishing between human and animal sources, and even between different animals. Washing powder constituents such as fluorescent whitening agents, sodium tripolyphosphate and linear alkyl benzenes, offer useful human source identifiers. It is unlikely that any single determinand will be useful in all situations, but statistical analysis of appropriate “baskets” of microbial and chemical determinands offers the possibility of identifying and apportioning human and animal faecal inputs to natural waters.

Jacques Cousteau and His World’s Inspiring Beauty - Alejandro Grajal (Conservation Biology, 1998)

The Endangered Species Act Is Analogous to Schindler's List - Donald A. Windsor (Conservation Biology, 1998)

Feminizing Turtle Embryos as a Conservation Tool - Marc Girondot; Hélène Fouillet; Claude Pieau Thinsp (Conservation Biology, 1998)
Most turtles have temperature‐dependent sex determination. With the intention to preserve endangered and threatened species, two management tools have been suggested: artificial incubation at either male‐ or female‐producing temperatures and introduction of many more females than males into populations by manipulating incubation temperatures to favor the production of female embryos. The use of estrogens during incubation has also been proposed to induce the development of females. We argue that in nature the incubation of eggs around the pivotal temperature is probably more frequent than generally recognized and leads to either phenotypic adult females or phenotypic adult males, even though the embryonic testis may present various degrees of intersexuality, including ovotestes as documented in artificial incubation. Observations of the turtle Emys orbicularis show that, after hatching, ovotestes tend to evolve into testes by regression, total or partial, of the ovarian‐like cortex. Testes with some immature oocytes at their surface have been observed in adult turtles, and they produce spermatozoa. Therefore, gonadal intersexuality apparently does not hinder the reproductive male function in adults. We draw attention to the danger of estrogenic treatment of embryos to produce females. In many cases, such treatment induces thin gonads (“hypogonads”) in which the volume of both cortex and medulla are reduced. Exogenous estrogens may also result in the arrest of lengthening of the Müllerian ducts and sometimes in the opening of their caudal end in the Wolffian ducts. Either process results in the inability of adult females to evacuate eggs from oviducts. We modeled the long‐term effects of introducing in a population a strongly female‐biased primary sex ratio (20 females to 1 male) for 30 years. Taking into account a genetic component of sex determination, as exemplified by the results of incubation at pivotal temperature, such a manipulation favors masculinizing alleles. When the manipulation is stopped, the primary sex ratio, as well as the adult sex ratio, becomes male‐biased—a result contrary to that expected—and the population size decreases. We recommend actions that protect adult populations and nesting sites and that improve the natural conditions of incubation in these sites rather than attempts to manipulate sex ratios. Feminización de Embriones de Tortugas Como una Herramienta de Conservación La mayoría de las tortugas poseen determinación sexual dependiente de la temperatura. Con la intención de preservar especies en peligro o amenazadas, dos herramientas de manejo han sido sugeridas: Incubación artificial a temperaturas tanto productoras de machos como de hembras y la introducción de mucho mas hembras que machos es las poblaciones mediante la manipulación de las temperaturas de incubación para facorecer la producción de embriones de hembras. El uso de estrógenos durante la incubación ha sido propuesto para inducir el desarrollo de hembras. Nosotros argumentamos que en la naturaleza, la incubación de huevos alrededor de temperaturas pivotes es probablemente mas frecuente de lo que en general se ha reconocido, tendiendo a producir organismos adultos fenotípicamente hembras o fenotípicamente machos, aunque los testículos podrían presentar diversos grados d intersexualidad, incluyendo ovotestis, como se ha documentado en incubaciones artificiales. Observaciones en la tortuga Emys orbicularis muestran que después de la eclosión los ovotestis tienden a evolucionar hacia testículos por regresión total o parcial de la corteza de tipo ovárica. En algunos organismos adultos se han observado testículos con algunos ovocitos inmaduros en la superficie, sin embargo estos producen espermatozoides. Por lo tanto, la intersexualidad gonadal aparentement no inhibe la función reproductiva del macho en adultos. Nosotros pusimos atención en el riesgo de producir embriones de hembras mediante trataminetos estrogénicos. En muchos casos, estos tratamientos indujeron gonadas pequeñas (Hipogónadas) en las cuales el volúmen tanto de la corteza como de la médula son muy reducidos. Estrógenos exógenos pueden también resultar en el arresto del elongamineto de los condutos Müllerianos y algunas veces de su apertura final en los conductos de Wolff, cualquiera de estos procesos imposibilita a los organismos adultos para la evacuación de huevos de los oviductos. Modelamos los efectos a largo plazo de la introducción en una población de sexos fuertemente sesgados hacis hembras (20 hembras; 1 macho) por 30 años. Tomando en consideración un componente genético de la determinación sexual, como se ha ejemplificado en los resultados de incubaciones a temperaturas pivote, favoreciendo los alelos masculinizantes. Cuando la manipulación es detenida, la proporción sexual primaria, así como la proporción sexual de los adultos se torna sesgada hacia machos. Un resultado contrario a lo esperado, disminuyendo el tamaño poblacional. Recommendamos acciones para proteger las poblaciones de adultos y los sitios de anidamiento para mejorar las condiciones de incubación natural, en lugar de llevar a cabo intentos de manipulación de las proporciones de sexos.

A Meta-Analysis of Forest Cover, Edge Effects, and Artificial Nest Predation Rates - Mitschka J. Hartley; Malcolm L. Hunter (Conservation Biology, 1998)

Proportions of Native and Introduced Brown Trout in Adjacent Fished and Unfished Spanish Rivers - J. L. Garcia-Marin; N. Sanz; C. Pla (Conservation Biology, 1998)

Movement Patterns and the Conservation of Amphibians Breeding in Small, Temporary Wetlands - C. Kenneth Dodd; Brian S. Cade (Conservation Biology, 1998)

Training Idiot Savants: The Lack of Human Dimensions in Conservation Biology - Susan K. Jacobson; Mallory D. Duff (Conservation Biology, 1998)

Density and Reproductive Success of California Towhees - Kathryn L. Purcell; Jared Verner (Conservation Biology, 1998)
Models of habitat selection commonly asume that higher‐quality source habitats will be occupied at higher densities than sink habitats. We examined an apparent sink habitat for California Towhees (Pipilo crissalis) in which densities are greater than in nearby source habitats. We estimated territory density using spot‐mapping and monitored nests of towhees in grazed and ungrazed oak‐pine woodland habitat. Breeding density of California Towhees was higher in ungrazed oak‐pine woodlands than in grazed areas, yet birds in the ungrazed site experienced lower reproductive success. Predation during the nestling period was primarily responsible for the lower nest success. Clutch size and the number of young fledged were also lower in the ungrazed site. Towhees selected nest sites with high foliage density and cover of live oaks (Quercus wislizenii) in the understory. Grazed sites had greater cover of live oak than ungrazed sites, and successful nests were more often built in live oak than in other plant species. This pattern could not be explained by dominant birds settling in grazed sites and excluding subdominant individuals because a large proportion of adults continued to settle in the ungrazed area. Towhees may have perceived the dense foliage of the ungrazed area as suitable due to abundant nest sites, cover, and food, resulting in an “ecological trap.” The resulting high density of birds there may have contributed to density‐dependent predation. Alternatively, towhees are not ideally adapted to their habitats because of their sedentary habits and site tenacity that is not affected by persistent nest loss. We stress the need to examine the reproductive success and productivity of individual species within specific habitat types. Densidad y Exito Reproductivo del Rascador Californiano Los modelos de selección de hábitat comunmente asumen que las fuentes de hábitat de alta calidad estarían ocupadas con densidades mas altas que en los hábitats pobres. Examinamos un hábitat aparentemente pobre para rascadores californianos (Pipilo crissalis) en el cual las densidades son mayores que en las fuentes de hábitat adyacentes. Estimamos las densidades territoriales utilizando mapeo de puntos y monitoreo de nidos en hábitats utilizados para pastoreo, así como en bosques de encino‐pino no pastoreados. La densidad de crianza de los rascadores fue mas alta en los bosques de encino‐pino libres de pastoreo que en las áreas utilizadas para pastoreo, sin embargo, las aves en el sitio sin pastoreo experimentaron un menor éxito reproductivo. La depredación durante el periodo de polluelos fue el motivo principal. El tamaño de puesta y el número de juveniles emplumando por nido fueron mas bajos en sitios libres de pastoreo. Los rascadores escogieron sitios de nidación con alta densidad de follaje y cobertura de encino siempreverde (Quercus wislizenii) en el sotobosque. Los sitios utilizados para pastoreo tuvieron mas encino siempreverde, en los cuales las aves construyeron mas nidos que en caulquier otra especie de planta. No se puede explicar este modelo en base al establecimiento de individuos dominantes en las áreas utilizadas para pastoreo y excluyendo a las aves menos dominantes, puesto que una proporción grande de adultos se estableció en sitios sin pastoreo. Es posible que los rascadores percibieron el follaje denso del sitio libre de pastoreo como apropiado, con abundantes sitios para nidación, cobertura y alimento, resultando en una “trampa ecológica.” La densidad alta de aves en el sitio sin pastoreo posiblemente contribuyó a una depredación denso‐dependiente. Alternativamente, los rascadores no estan idealmente adaptados a sus hábitats debido a sus hábitos sedentarios y a su tenacidad por sitios, misma que no es afectada por una pérdida persistene de nidos. Enfatizámos la necesidad de analizar el éxito reproductivo y la productividad de especies a nivel individual dentro de tipos de hábitat específicos.

Influence of Complex Sex Determination on Demographic Stochasticity and Population Viability - Paul Leberg (Conservation Biology, 1998)

The Impact of Diving on Rocky Sublittoral Communities: A Case Study of a Bryozoan Population - Joaquim Garrabou; Enric Sala; Antoni Arcas; Mikel Zabala (Conservation Biology, 1998)
In 1992 a diving buoy was installed within a marine reserve off the northeastern coast of Spain, where diving had not previously been permitted. We monitored the effects of diving on a colonial bryozoan (Pentapora fascialis) and carried out the study on two distinct benthic habitats, boulders and vertical walls. We used a “beyond before‐after/control‐impact” sampling design in which one potentially affected and several control locations were sampled simultaneously before and after the installation of the diving buoy. We hypothesized that diving has three major impacts: (1) it decreases the density of P. fascialis, (2) it reduces the mean size of P. fascialis colonies, and (3) it restricts P. fascialis colonies to cryptic positions. Surveys of diving activity conducted from 1992 to 1995 showed that diving increased 60‐fold at the impact location. Analysis revealed a significant decrease in density of colonies of P. fascialis (~50% from 1992 to 1993) in both communites at the impact location 1 year after the start of the diving disturbance. The effect of diving on the size of colonies was not clear. The analysis revealed no general pattern of significant impact, although the impact location suffered a general loss of large colonies. P. fascialis colonies on boulders were more numerous in more cryptic positions once diving activity began at the impact location. On walls, although there was a reduction of more exposed colonies after the start of the disturbance ( from 1992 to 1993), the changes over time were not significant. The control locations showed no significant changes in the distribution of the degree of exposure of colonies over time on either community. The effects of diving differed in the two communities studied. The impact on boulders was stronger than that on the walls. This may be explained by the protection provided by the dense canopy of gorgonian (Paramuricea clavata), the largest organism on vertical walls. On boulders erosion was continuous and cumulative. On walls, however, once the divers had eliminated the most exposed colonies—mainly the epibionts—the arboreal structure of the gorgonians prevented divers from coming into direct contact with the communities and reduced the risk of erosion. Sublittoral benthic communities in the northwestern Mediterranean constituted by sessile organisms with fragile calcareous or corneous skeletons are not adapted to the severe disturbances caused by continuous and intense diving. Recovery after such a disturbance appears to be slow and difficult. Current diving activity may not allow disturbed communities at diving sites to recover. The results of this experiment should be considered by managers and the data used to evaluate the models on which management decisions are based. El Impacto del Buceo en Comunidades Sublitorales sobre Sustrato Rocoso: El Caso de una Población de Briozoos En 1992 se instaló una boya para el buceo en un lugar previamente no frecuentado por los buceadores, dentro de una reserva marina en el nordeste de España donde el buceo está regulado, lo que supuso una oportunidad experimental para testar el impacto del buceo sobre las comunidades bentónicas. Monitorizamos un briozoo colonial (Pentapora fascialis), susceptible de ser erosionado por los escafandristas. Este estudio se realizó en dos hábitats diferentes (fondos de bloques y paredes verticales). En este estudio realizamos un diseño de muestreo “Beyond BACI,” en el cual la localidad potencialmente impactada (impact) y algunas localidades control fueron muestreadas contemporáneamente antes (una vez en 1992) y después (3 veces, entre 1993‐1995) de la instalación de la boya para el buceo. Formulamos la hipótesis de que el buceo provoca tres impactos principales: (1) el buceo disminuye la densidad de P. fascialis, (2) reduce la talla media de las colonias de P. fascialis, y (3) restringe las colonias de P. fascialis a posiciones crípticas. El control de las inmersiones realizadas durante el periodo 1992‐1995 mostró un aumento del buceo (×60) en la localidad impactada. El análisis reveló una disminución significativa de la densidad de colonias de P. fascialis (~50% entre 1992 y 1993) en ambas comunidades en la localidad impactada tras el inicio de la perturbación humana. El efecto del buceo sobre la talla de las colonias no fue claro: el análisis no reveló ningún patrón general de impacto significativo, aunque la localidad impactada sufrió una pérdida general de colonias grandes. En los fondos de bloques de la localidad impactada, las colonias de P. fascialis se restringieron claramente a posiciones más crípticas tras el inicio del buceo. En las paredes verticales, aunque se produjo una reducción del número de colonias más expuestas a los buceadores tras el inicio del buceo (entre 1992 y 1993), los cambios temporales no fueron significativos. En las localidades control no hubo cambios temporales significativos en la distribución de los grados de exposición de las colonias en ninguna comunidad. Los efectos del buceo difirieron entre las dos comunidades estudiadas: en los bloques el impacto fue más intenso que en las paredes verticales. Esto puede ser explicado por la protección proveída por el dosel de la gorgonia Paramuricea clavata, el organismo de mayor tamaño en la comunidad de las paredes verticales. En los bloques, la erosión es contínua y acumulativa. En las paredes, sin embargo, una vez los buceadores han eliminado las colonias más expuestas, principalmente las epibiontes, la estructura arbórea de las gorgonias evita el contacto directo de los buceadores y disminuye el riesgo de erosión. Las comunidades bentónicas infra‐ y circalitorales del Mediterráneo noroccidental constituídas por organismos sésiles con frágiles esqueletos calcáreos o córneos no se encuentran adaptadas a las severas perturbaciones causadas por el buceo intensivo y continuado. La recuperación de las comunidades tras tal perturbación parece muy problemática. Las actuales tasas de frecuentación por buceadores pueden impedir la recuperación de las comunidades perturbadas. Esta situación experimental debería ser considerada como parte de la gestión de la reserva, y su resultado podría ser usado para evaluar los modelos en los que está basada.

Extinction and Persistence of Rare Orchids in Veracruz, Mexico - Victoria Sosa; Teodoro Platas (Conservation Biology, 1998)