Nitrate movement and removal along a shallow groundwater flow path in a riparian wetland within a sheep‐grazed pastoral catchment: Results of a tracer study - Douglas A. Burns; Long Nguyen (New Zealand Journal of Marine and Freshwater Research, 2002)
The movement and removal of nitrate (NO 3 ‐ ) along a groundwater flow path within a riparian wetland was investigated during a 24‐day period in late autumn‐early winter, using a lithium bromide (LiBr)‐potassium nitrate (KNO 3 ) tracer solution containing 19 200 mg/litre as Br ‐ and 193.8 mg/litre as NO 3 ‐N. The tracer solution was added as an instantaneous dose of tracer solution at a depth of 10–20 cm to four injection wells in two 1 m 2 plots within a sheep‐grazed pastoral catchment at the Whatawhata Agricultural Research Centre near Hamilton, New Zealand. Bromide and NO 3 ‐N concentrations were measured periodically in: (1) wetland groundwater samples from piezometers installed at 15 and 30 cm depths and located at 30, 60, and 100 cm down gradient from the injection wells; and (2) surface flow samples. Peak concentrations of 50–250 mg/litre of Br ‐ and 0.2–1.1 mg/litre of NO 3 ‐N were reached within 1–2 days after application at most piezometers. Nitrate concentrations decreased thereafter more sharply than did those of Br ‐ , resulting in decreased NO 3 ‐N/Br ‐ ratios from Days 2 through 7. More than 99% of groundwater samples collected after the tracer application had NO 3 ‐N/Br ‐ less than the value in the tracer solution indicating removal of NO3‐N during transport. Mass flux estimates indicated removal of >90% of added NO 3 ‐N along the 100 cm flow path from the injection, with essentially all of the NO 3 ‐ removed within the first 30 cm of transport. On Days 10 and 24, just after rain events, surface flow from the experimental plots had greatly elevated NO 3 ‐N concentrations that were not accompanied by correspondingly elevated Br ‐ concentrations, indicating that NO 3 ‐N originating from the surrounding catchment was transported over the wetland surface with little penetration or mixing with wetland groundwater. Despite a significant capacity for NO 3 ‐N removal from shallow groundwater equivalent to an annualised value of 50 kg/ha in these wetland study plots, large amounts of NO3‐N from the catchment are likely to move over the wetland surface during rain events without adequate soil contact time for efficient denitrification and retention.

Spatial and temporal distribution of landlocked Galaxias maculatus and Galaxias platei (Pisces: Galaxiidae) in a lake in the South American Andes - Juan P. Barriga; Miguel A. Battini; Patricio J. Macchi; Daniela Milano; Victor E. Cussac (New Zealand Journal of Marine and Freshwater Research, 2002)
Galaxiids are present in many of the Andean lakes in southern South America. We studied landlocked Galaxias maculatus (Jenyns) and Galaxias platei Steindachner populations in a deep oligotrophic lake (Lake Gutiérrez, Patagonia, Argentina). Their temporal and spatial distribution, intralacustrine movements (horizontal and vertical), and spawning periods were analysed using several sampling techniques (ichthyoplankton net, seine net, gill net, and baited benthic taps). We identified the early life stages of both species based on their morphology and otolith shape. The free embryos of both species migrate to the limnetic zone, where they coexist as larvae, facing the same food availability and probably the same predation risk. Each species then moves on to its own juvenile and adult habitat: the littoral and benthic zone for G. maculatus and only the deeper benthic zone for G. platei . Their adult habitats and part of their spawning periods partly overlap.

Two new species of Turbanellidae (Gastrotricha: Macrodasyida) from a high‐energy beach on North Stradbroke Island, Australia - Rick Hochberg (New Zealand Journal of Marine and Freshwater Research, 2002)
s Two new species of macrodasyidan gastrotrichs were found in coarse intertidal sands of Frenchmans Beach, a high‐energy beach facing the South Pacific Ocean, on the eastern side of North Stradbroke Island, Australia. Paraturbanella stradbroki n. sp. is up to 665 μm long and is distinguished from its congeners by the shape of the head, the presence of dorsal and lateral adhesive tubes, the pattern of locomotor cilia, and the lack of piston pits and a median caudal cone. Turbanella brusci n. sp. is up to 1002 μm long and is characterised by the shape of the head, the presence of three paired columns of dorsal, lateral, and ventrolateral adhesive tubes, a median caudal cone, and the lack of “cirrata” tubes. The ventrolateral adhesive tubes are symmetrically aligned beneath the lateral adhesive tubes and are considered unique to the genus. This constitutes the first report of Paraturbanella and Turbanella from Australian waters.

Water quality and sediment and nutrient export from New Zealand hill‐land catchments of contrasting land use - John M. Quinn; Morag J. Stroud (New Zealand Journal of Marine and Freshwater Research, 2002)
Measurements were made of suspended sediment (SS), volatile suspended solids, dissolved organic carbon (DOC), nitrogen (N) and phosphorus (P) concentrations, turbidity, black disk visibility, pH, alkalinity, and temperature, at monthly intervals for 2–5 years on nine streams draining catchments with pasture, pine plantation, and native forest land uses. Stream flow and flow‐weighted concentrations of SS, N, and P were also measured for up to 2 years from pasture, native forest, and mixed land‐use catchments enabling calculation of export (kg ha ‐1 yr ‐1 ). During 1996–97, export from the pasture stream was 2.5‐ to 7‐fold higher for SS (988), total P (1.50), total Kjeldahl N (5.65), nitrate N (4.37), and ammoniacal N (0.34) than from the stream draining native forest. In contrast, export of DOC (25.5) and dissolved reactive P (DRP) (0.25) from the pasture stream were within 20% of the native stream's values. Export of SS and nutrients (except DRP) from the pasture catchment was 4‐ to 15‐fold higher during the winters of 1995 and 1996 than winter 1997 when rainfall was half the normal level. Streams draining native forest had lower temperature, sediment, and nutrient concentrations (except DRP), and higher water clarity, than those draining pine forest and pasture. A pine/scrub stream had the highest SS and turbidity and lowest DRP, pH, and alkalinity. Pasture streams had the highest concentrations of all N species (geometric means 2‐to 4‐fold > native), total P, and DOC, and also showed the greatest variation in water quality attributes in relation to season and flow. The influences of land use were attributable to differences in both source materials of sediment and nutrients available for transport and changes in rates of in‐stream processing.

Temperature and salinity mean and variability within the subtropical front over the Chatham rise, New Zealand - Stephen M. Chiswell (New Zealand Journal of Marine and Freshwater Research, 2002)
Estimates are made of the mean and variability in temperature and salinity across the Subtropical Front along 178°30'E, east of New Zealand. These estimates are made from six sections taken over 5 years, but biased towards spring and autumn sampling. Monte‐Carlo simulations of the potential errors introduced by this sampling suggest that the mean fields can be reasonably well determined, but the annual cycles have large relative error. April 1999 residuals were anomalously warm and saline compared with the other five sections. These anomalies may be linked to an increased strength of the Wairarapa Eddy at that time.

Occurrence of dolphinfish ( Coryphaena hippurus ) and pompano dolphinfish ( Coryphaena equiselis ) in the Canary islands revealed by genetic analysis - J. M. Pujolar; C. Pla (New Zealand Journal of Marine and Freshwater Research, 2002)
Genetic analyses of samples of the genus Coryphaena caught in the Canary Islands clearly revealed the existence of two different species, C. hippurus , Linnaeus 1758 and C. equiselis , Linnaeus 1758. Each species was fixed for different alleles at 11 out of 30 loci and a large genetic distance (0.814) was found between the two species. Previously only C. hippurus has been reported in the Canary Islands fishery. The two Coryphaena species are similar in appearance, so C. equiselis can be confused with C. hippurus by fishers, especially small specimens C. hippurus and C. equiselis .

Diet of giant kokopu, Galaxias argenteus - Martin L. Bonnett; Paul W. Lambert (New Zealand Journal of Marine and Freshwater Research, 2002)
The stomach contents of 105 preserved specimens of giant kokopu, Galaxias argenteus (Gmelin 1789), collected from various locations around New Zealand between c. 1963 and 1994, were used to investigate giant kokopu diet. A total of 76 food taxa, predominantly invertebrates, were identified and categorised as either of aquatic or terrestrial origin from the 91 stomachs that contained food items. Aquatic Trichoptera, Gastropoda, and Hemiptera comprised 29.1, 12.6, and 14.4% by abundance respectively, and terrestrial Coleoptera 12.2% by abundance. Adult terrestrial Coleoptera were the most commonly occurring taxa, and were found in 59% of the stomachs that contained food. Food items of aquatic origin occurred in 94.5% of the giant kokopu stomachs that contained food and comprised 74.9% of the items by abundance. Although fewer items of terrestrial origin were encountered, they nevertheless appeared to be a significant component of the diet, and occurred in 83.5% of the giant kokopu stomachs that contained food, and comprised 25.1% of the items by abundance. Items of terrestrial origin occurred slightly more frequently in giant kokopu from lotic habitats than from lentic habitats. The significance of terrestrial food may be associated with giant kokopu preference for habitats with riparian cover. Fish also appeared to be a significant component of the diet, as 26% of the giant kokopu examined contained fish remains. Giant kokopu are probably best described as generalist feeders, as they utilise a wide range of foods of both aquatic and terrestrial origin.

Ocean‐tide loading and Earth tides around New Zealand - Derek G. Goring; Roy A. Walters (New Zealand Journal of Marine and Freshwater Research, 2002)
Cotidal charts of ocean‐tide loading and Earth tides for the New Zealand region are presented for eight constituents (M 2 , S 2 , N 2 , K 2 , K 1 , O 1 , P 1 , Q 1 ). Ocean‐tide loadings were calculated by evaluating a convolution integral between tide models (global and local) and a Green's function that describes the response of the Earth to tide loading. Earth tides were calculated from the tide‐generating potential. The ocean‐tide loadings are a maximum to the north of New Zealand for M 2 and N 2 and in the western Cook Strait region for S 2 and K 2 . The diurnal ocean‐tide loadings are dominated by amphidromes east of the Chatham Islands (K 1 and P 1 ) and north of Bay of Plenty (O 1 and Q 1 ). Diurnal Earth tides are a maximum at 45°S and vary only slightly in amplitude and phase over New Zealand; semidiurnal Earth tides increase from south to north.

In‐stream habitat suitability criteria for feeding inanga ( Galaxias maculatus ) - I. G. Jowett (New Zealand Journal of Marine and Freshwater Research, 2002)
Inanga ( Galaxias maculatus Jenyns) are the basis of an important recreational and commercial freshwater fishery that has declined over the past 100 years, probably because of habitat degradation in developed areas. Maintenance of suitable stream flows for inanga is one means of protecting the fishery. Observations of habitat use by drift‐feeding inanga were made in three streams. Most feeding inanga were stationary in the current taking food items from the drift and sometimes from the surface. Drift‐feeding locations were related to current patterns and water velocity, with inanga feeding at locations where the current concentrated food, and where water velocities were sufficiently low to allow the fish to hold position. The mean feeding velocity did not vary significantly between streams, although the range of velocities used did. Optimum feeding velocities were 0.03–0.07 m s ‐1 , and were comparable with brown trout ( Salmo trutta ) feeding velocities, when adjusted for the differences in fish size. Depth use was very different between streams and this was attributed to the variation in available habitat. Depths greater than 0.3 m were optimum, with some use of depths between 0.1 and 0.3 m. It is suggested that inanga suitability criteria are dictated by biological factors, such as swimming ability and bio‐energetic requirements, rather than the river the fish is living in and that it is necessary to collect habitat use and availability data in a wide range of stream types to define optimal habitat and suitability criteria for generalised application.

Effect of storm drain discharge on the soft shore ecology of Porirua Inlet, New Zealand - Kathryn J. Botherway; Jonathan P. A. Gardner (New Zealand Journal of Marine and Freshwater Research, 2002)
The effect of storm drain discharge on the ecology of the soft shore community near the Semple Street outfall in Porirua Inlet, New Zealand, was investigated from December 1998 to April 1999. Biological community structure, sedimentary properties, and heavy metal concentrations of surficial sediments were examined at increasing distance (5, 90, 140 m) from the storm drain at two (upper and lower) shore heights (total of six sites). Concentrations of copper (Cu), lead (Pb), and zinc (Zn) at nine sites from the storm drain to the mouth of the inlet were estimated in April 1999. Typically, mean numbers of individuals decreased, whereas mean numbers of taxa, and the Shannon‐Wiener diversity index increased with increasing distance from the storm drain. Analysis of variance revealed that the 5, 90, and 140 m sites at both tidal heights exhibited small but significant differences in community structure which were attributable to differences in species abundance, rather than to differences in the suite of species which characterise these sites. It was not possible to identify temporal trends in the data set. Analysis of similarities revealed significant differences in species abundance among the three sites for the high shore, the low shore, and both tidal heights combined. Sites furthest apart (5 versus 140 m) exhibited the greatest, and sites closest together (90 versus 140 m) exhibited the least, difference in biological community structure, suggesting that storm drain outflow modifies benthic community composition immediately in front of the drain and up to

Detecting patterns in hyporheic community structure: Does sampling method alter the story? - M. R. Scarsbrook; J. Halliday (New Zealand Journal of Marine and Freshwater Research, 2002)
Hyporheic invertebrates were sampled in six small headwater streams draining pine, pasture, and native forest catchments. Sites were sampled in autumn and spring using three different hyporheic sampling methods (colonisation pots, pump sampling, and freeze‐coring). Total invertebrate abundance and taxon richness differed significantly among sites on both sampling occasions for pump samples, whereas freeze‐coring did not discriminate among sites, and pot samples showed significant differences in autumn, but not in spring. Differences among sites with respect to community composition were not consistent between sampling methods. Community ordination indicated that samples from colonisation pots tended to group together, whereas pump and freeze core samples were widely separated. Differences across land uses were also apparent (native forest sites formed a distinct cluster separated from pine and pasture sites). Results suggest that colonisation pots may provide a pathway for the entry of epigean organisms into the hyporheic zone even when hydraulic connectivity between surface and hyporheic zones is low. Invertebrate abundance was very low in pump samples, and this method also captured the fewest taxa of the three methods. The size bias known to exist with pump sampling techniques may restrict the usefulness of the method when comparing streams of differing hydraulic conductivity.

Wairarapa Coastal Current influence on sea surface temperature in Hawke Bay, New Zealand - Stephen M. Chiswell (New Zealand Journal of Marine and Freshwater Research, 2002)
The Wairarapa Coastal Current (WCC) flows along the east coast of the North Island, New Zealand. This current has been relatively little studied, and there are few direct measurements of its mean and variability. Here, an indirect method is used to gain some insight into the WCC variability and its effect on coastal temperature. Eight years of coastal temperature from Napier in Hawke Bay are modelled as a bivariate linear expansion of alongshore windstress and solar radiation. In the frequency domain, the modelled temperatures are coherent with observed temperatures, and in the time domain, they are positively correlated for 80% of the time. The model results suggest both that variations in the WCC are wind‐driven, and that alongshore advection accounts for most of the temperature change at Napier. Periods when the modelled temperature is not correlated with observed temperature could be because of episodes of enhanced upwelling, or large‐scale influences breaking down the alongshore temperature gradient.

Distribution and biomass of benthic microalgae in Manukau Harbour, New Zealand - L. B. Cahoon; K. A. Safi (New Zealand Journal of Marine and Freshwater Research, 2002)
Benthic microalgal biomass (as sediment chlorophyll a (Chl. a ), by spectrophotometry) and taxonomic composition (by HPLC pigments analysis) were investigated at intertidal locations throughout Manukau Harbour, North Island, New Zealand. Benthic microalgal biomass averaged 97.5 mg Chl. a m ‐2 for all sediment samples. Benthic microalgal biomass was higher in sediments containing at least some sand than in muddy sediments, in contrast to previous findings from Manukau Harbour. Loading of fine sediments from erosion within the harbour's basin may, therefore, affect the amount and distribution of benthic microalgal biomass in the harbour. Average benthic microalgal biomass for the entire area of the harbour was at least 62.5 mg Chl. a m ‐2 . The latter value is at least 4 times higher than mean annual, spatially integrated phytoplankton biomass in Manukau Harbour, suggesting that benthic microalgae are a more important food source for estuarine consumers. High fucoxanthin:chlorophyll a ratios indicated that benthic microalgae were primarily diatoms. The physical characteristics of Manukau Harbour and similarity in taxonomic composition of the phytoplankton and benthic microalgae suggest that resuspended benthic microalgae are an important component of the harbour's phytoplankton biomass.

Use of classification and regression tree (CART) analysis with chemical faecal indicators to determine sources of contamination - Jan Gregor; Nick Garrett; Brent Gilpin; Cliff Randall; Darren Saunders (New Zealand Journal of Marine and Freshwater Research, 2002)
Both human and non‐human faecal contamination of environmental waters pose a risk to human health that can be reduced if the source can be identified and responsibility for mitigation accepted. Traditional microbiological indicators are rarely adequate for source identification but some chemical indicators offer promise. In this work, the similarities and differences of selected chemical profiles of different faecal effluent types have been modelled using classification and regression tree (CART) analysis. Human effluents can be distinguished from non‐human effluents by the presence of fluorescent whitening agents, and the concentrations or ratios of concentrations of the faecal stanols coprostanol and 24‐ethylcoprostanol can distinguish most of the non‐human effluent types considered. To allow for the effect of variable dilution when effluents enter environmental waters, ratios of concentrations will be required to establish a model, and a model more complex than CART will be required to apportion multiple effluent‐type contamination.

Influence of diet and temperature on physiological energetics of Chorus giganteus (Gastropoda: Muricidae) during reproductive conditioning - J. M. Navarro; G. E. Leiva; C. S. Gallardo; C. Varela (New Zealand Journal of Marine and Freshwater Research, 2002)
The influence of two bivalve diets ( Mytilus chilensis “chorito” and Tagelus dombeii “navajuela”) at three temperatures (13, 15, and 18°C) was studied during the reproductive conditioning of Chorus giganteus (Lesson, 1829). Energy budgets were determined taking into account energy acquisition (ingestion and absorption) and energy expenditure (oxygen consumption, ammonia production, and energy placed into mucus production and egg laying). Relative physiological condition was assessed by calculating the scope for growth index (SFG). Diet and temperature both played key roles in the physiological energetic and reproductive conditioning of this snail. Tagelus was the preferred prey, probably because of its greater vulnerability to predatory attack by C. giganteus . The highest feeding rate was observed at 15°C, coinciding with optimal growth. Absorption efficiency was similar with both diets, despite the differential preference in prey. Temperature had no effect on oxygen uptake, but increased as the snails fed on Tagelus during the reproductive conditioning period. Diet was the main factor affecting SFG, and temperature, although significant, accounted for a lower percentage of variation in SFG. Highest growth rates were observed at 15°C on a Tagelus diet. Reproductive effort, measured as the proportion of the total energy budget of an organism that is allocated to reproduction, was highest at 18°C with a Tagelus diet. Energy would not be allocated for reproduction when the snails were fed with M. chilensis , as SFG was negative at all three temperatures.

A new species of bathyal elasipod sea cucumber from New Zealand (Echinodermata: Holothuroidea) - David L. Pawson (New Zealand Journal of Marine and Freshwater Research, 2002)
Orphnurgus dorisae new species is described from bathyal depths to the north of New Zealand, near the Kermadec Islands. It is distinctive in possessing spatulate rods and spinous rods dorsally, and spinous rods and perforated plates ventrally. A key to Orphnurgus species is provided. Egg size suggests that this species, and other Orphnurgus species, may have planktonic lecithotrophic embryos.

Sink rate of baited hooks during deployment of a pelagic longline from a New Zealand fishing vessel - Simon Anderson; Brian Mcardle (New Zealand Journal of Marine and Freshwater Research, 2002)
The sink rate of baited hooks during the deployment of a pelagic longline was determined using time depth recorders. This study was undertaken to determine how long baited hooks are within the known diving ranges of seabirds. During the vessel's normal fishing operations the unweighted baited hooks reached a mean depth of 5.57 m, 30 s after being deployed. The tori line aerial section covered the longline for a mean time of 29.3 s. With the addition of a 60 g lead swivel, the mean baited hook depth attained more than doubled to 13.44 m, and a further trial using a lead core cord in the snood configuration showed a small but significant increase in hook depth over the unweighted control (7.27 m). An increase in wind speed caused the baited hooks to sink faster (0.54 m for each Beaufort unit increase in wind speed). There was also evidence that the apparent wind direction while the vessel is setting also has an effect on the depths realised, but swell height had no detectable effect. The temperature of the bait also significantly affected the hook depth: partially thawed baits sank faster than thawed baits. A 1°C rise in bait temperature reduced the depth by 0.19 m. During normal line setting on this vessel using unweighted branchlines and a tori line, a considerable proportion of the baited hooks are within the known diving range of sooty shearwaters (Puffinus griseus) , white chinned petrels (Procellaria aequinoctialis) , shy albatross (Thalassarche cauta) , black browed albatross (T. melanophrys) , grey headed albatross (T. chrysostoma) , and light mantled sooty albatross (Phoebetria palpebrata) . The addition of a 60 g weight removes the baited hooks from the recorded diving range of all of these species except sooty shearwaters. Investigating the behaviour of different gear configurations along with evaluating the effect that environmental conditions have on the deployment of a longline will greatly add to our understanding of why some seabirds are caught.

Effects of logging with and without riparian strips on fish species abundance, mean size, and the structure of native fish assemblages in Coromandel, New Zealand, streams - David K. Rowe; Joshua Smith; John Quinn; Ian Boothroyd (New Zealand Journal of Marine and Freshwater Research, 2002)
We determined the effects of logging, both with and without a riparian buffer strip, on the native fish fauna at 27 stream sites in an exotic pine (mainly Pinus radiata) forest on the Coromandel Peninsula, New Zealand. Fish abundance at the logged sites was compared with reference sites in both unlogged pine and native forest. The abundance of Anguilla dieffenbachii (Gray) and Anguilla australis (Richardson) was not significantly affected by logging. However, the abundance of Galaxias fasciatus (Gray) and Gobiomorphus huttoni (Ogilby) was. There were fewer Ga. fasciatus at the logged sites without buffers than at the reference sites, but more at the logged sites with buffers. The abundance of Go. huttoni was higher at the logged sites than at the reference sites, and was highest at the logged sites with riparian buffers. Overall, the different, species‐specific responses to logging maximised total fish numbers at the logged sites. As total fish numbers, the abundance of Ga. fasciatus , and species equitability, a measure of fish assemblage structure, were all highest at the logged sites with riparian buffer strips, we concluded that riparian strips enhanced the native fish community of streams within these logged catchments.

Response of New Zealand waters to the Peru tsunami of 23 June 2001 - Derek G. Goring (New Zealand Journal of Marine and Freshwater Research, 2002)
The Peru tsunami of 23 June 2001 arrived at New Zealand's east coast 16.5 h after generation, having travelled c. 8000 km across the Pacific Ocean. All the sea level recorders on the east coast recorded waves, but the response was highly variable, with the greatest response in Lyttelton Harbour, where the water fell by 26 cm, then rose over the next hour to peak at 30 cm. None of the recorders on the west coast felt the tsunami. The time scale of the waves was between 2 and 20 min and they persisted for more than 20 h after the first waves arrived, before starting to slowly decay. In some places, like Pegasus Bay, the tsunami excited local seiche, but these waves quickly dissipated. Analysis of data collected at 1‐min intervals, instead of the standard 5‐min intervals, indicated that information is lost when sampling tsunami at 5‐min intervals.

Movements and habitats of adult lamprey ( Geotria australis) in two New Zealand waterways - D. J. Jellyman; G. J. Glova; J. R. E. Sykes (New Zealand Journal of Marine and Freshwater Research, 2002)
The spring upstream spawning migration of the Southern Hemisphere lamprey, Geotria australis Gray, was investigated by monitoring movements of radio‐tagged lampreys in two South Island, New Zealand, catchments of contrasting size (Okuti Stream, a small coastal stream and the Mataura River, a medium‐sized lowland river). A total of 65 lampreys were radio‐tagged and tracked by foot and helicopter between 1998 and 1999. Retention of the externally‐mounted tags proved a problem, and lampreys were tracked for a maximum of 56 days. Most movement was recorded within a few days of release; movement was generally up stream although a number of fish also periodically moved down stream. Maximum daily movement in the Okuti Stream was 0.45 km compared with 12.6 km in the Mataura River; upstream movement was stimulated by increased flow but curtailed by large floods. During the day, lampreys were generally associated with bankside debris cover. The seven fish that moved furthest up the Mataura River all entered the same tributary, presumably in response to odours of their conspecifics. Thirteen lampreys retained for a year and released as nearly sexually mature, moved little from their place of liberation and possible reasons for this are discussed.

Taxonomic revision of the genus Latrunculia Du Bocage (Porifera: Demospongiae: Latrunculiidae) in New Zealand - Belinda Alvarez; Patricia R. Bergquist; Christopher N. Battershill (New Zealand Journal of Marine and Freshwater Research, 2002)
The genus Latrunculia in New Zealand was believed to be represented by at least three species: L. brevis Ridley & Dendy and two undescribed species. However, results from recent studies indicate that the genus contained a complex of at least eight genetically distinct species. In this paper we revise the taxonomy of Latrunculia in New Zealand and describe nine new species. Eight of these were previously identified using genetic techniques (i.e., L. kaakaariki sp. nov., L. duckworthi sp. nov., L. procumbens sp. nov., L. wellingtonensis sp. nov., L. kaikoura sp. nov., L. triverticillata sp. nov., L. fiordensis sp. nov., and L. millerae sp. nov.) and one (L. oxydiscorhabda sp. nov.) was distinguished based only on morphological differences. The species described fall into two morphological groups, spinispiraefera and triverticillata , which can be diagnosed by the number of whorls present along the discorhabd axis. The status of L. brevis , and other subantarctic species (i.e., Latrunculia bocagei, L. antarctica, L. lendenfeldi, L. spinispiraefera) is discussed; all of these species are considered to be valid but not conspecific with any of the species described here.

Evaluation of invertebrate biometrics and the influence of subsample size using data from some Westland, New Zealand, lowland streams - Ian C. Duggan; Kevin J. Collier; Paul W. Lambert (New Zealand Journal of Marine and Freshwater Research, 2002)
The accuracy and variability of six invertebrate biometrics (taxa richness, number of Ephemeroptera, Plecoptera, and Trichoptera (EPT) taxa, % EPT abundance, % dominant taxon, the Macroinvertebrate Community Index (MCI), and Quantitative MCI (QMCI)) were examined using data from four Westland, New Zealand, streams. All metrics except QMCI differed significantly among sites. Taxa richness and number of EPT taxa distinguished the most impacted site from the remaining sites. Significant temporal differences among streams occurred for % EPT abundance and MCI, and there were interaction effects for these plus % dominant taxon and QMCI, indicating that any differences among sites varied through time. Within individual streams, MCI and QMCI had low ( Metric values obtained from random 100‐count subsamples with replacement had low variability (

Effects of turbidity on the feeding ability of adult, riverine smelt ( Retropinna retropinna) and inanga ( Galaxias maculatus) - David K. Rowe; Joshua Smith; Erica Williams (New Zealand Journal of Marine and Freshwater Research, 2002)
Laboratory tank experiments indicated that turbidity levels up to 160 Nephelometric Turbidity Units (NTU) did not reduce the feeding rates of adult smelt ( Retropinna retropinna Richardson), or inanga (Galaxias maculatus Jenyns), on Daphnia sp. Mean feeding rates were higher for inanga than for smelt. However, the lower rates for smelt were related to the greater variation in individual feeding rates. Specifically, a few fish fed intensively while most did not. As the feeding ability of both species was unaffected by turbidity levels up to 160 NTU, they were less sensitive to turbidity than juvenile banded kokopu ( Galaxias fasciatus Gray). Juvenile banded kokopu should therefore be used as the benchmark species for setting turbidity guidelines to protect native fish in rivers where this species is present. Both juvenile and adult rainbow trout ( Oncorhynchus mykiss Richardson) appear to be more sensitive to turbidity than adult inanga and smelt, so should be used as benchmark species in all other waters.

Selected trace elements in Stockton, New Zealand, waters - E. Alarcón León; R. G. Anstiss (New Zealand Journal of Marine and Freshwater Research, 2002)
Ni, Mn, As, Pb, Cd, Cr, Cu, Hg, Se, Al, Zn, Fe, SO 4 2‐ , hardness (calc.) in addition to pH, total dissolved solids (TDS), and total suspended solids (TSS) were measured at 18 (11 surface and 7 subsurface) sampling sites (which were each assigned a semi‐quantitative Mudstone Index (MI)) from 20 days over 9 months in the waters which drain the Stockton coal mine area on the Stockton Plateau, New Zealand. Trace element, TDS and TSS concentrations were found to be elevated and pH depressed consistent with acid mine drainage (AMD) and were characterised by significant variability due to environmental processes. Frequent concentration spikes in surface and subsurface waters occurred which sometimes exceeded maximum acceptable values (MAV) and/or aesthetic guideline values (GV) including a number of toxic trace elements. Mean concentrations of Ni and Mn in both surface and subsurface waters and As and Cd in subsurface waters exceeded MAVs. Mean concentrations of Mn, Al, Fe, SO 4 2‐ , and pH in both surface and subsurface waters exceeded GVs. There tends to be higher trace element and TDS concentrations where there are more mudstones (higher MI) with lower pHs. It is recommended that any further studies focus on geographic distribution, concentration fluctuation factors, movement, and possible exposure issues.

Diet of the crayfish Paranephrops zealandicus in bush and pasture streams: Insights from stable isotopes and stomach analysis - John W. Hollows; Colin R. Townsend; Kevin J. Collier (New Zealand Journal of Marine and Freshwater Research, 2002)
Crayfish ( Paranephrops zealandicus White) stomachs from streams in both native bush (mainly tree leaves and dicotyledonous seeds) and exotic pasture settings (mainly grass stems and monocotyledonous seeds) were dominated by allochthonous material. More detritus occurred in stomachs in autumn‐winter than in spring‐summer, but quantities were similar in crayfish from native bush and pasture streams. The stomachs of larger crayfish contained a significantly greater proportion of detritus than smaller individuals. Aquatic invertebrates were the second most abundant dietary category by volume, with highest values in winter, but there were no significant differences between land uses or crayfish size classes. A wide range of invertebrates was eaten by crayfish, with mayfly nymphs, chironomid larvae, and snails predominating. The latter were numerically more prominent in crayfish from bush than pasture streams. Terrestrial invertebrates were recorded from 4% of stomachs, but there were no significant differences in relation to land use, season, or crayfish size class. Despite aquatic invertebrates making up 13 C and perhaps of microfloral origin, seems to be an important energy source for crayfish in both stream types.

Influence of fluctuating lake levels and water clarity on trout populations in littoral zones of New Zealand alpine lakes - Gavin D. James; Eric Graynoth (New Zealand Journal of Marine and Freshwater Research, 2002)
Brown trout (Salmo trutta Linnaeus 1758) and rainbow trout (Oncorhynchus mykiss Richardson 1836) populations in littoral zones of eight South Island, New Zealand alpine lakes were compared using gill and seine net sampling during summer. Lakes were selected to provide a matrix of lake level and water clarity variations and to assess how these variables influenced trout abundance (as reflected by catch rate), depth distribution, and size. Brown trout were small and in poor condition in three turbid lakes with shallow littoral zones and were scarce in one of these with a 14 m fluctuation. Although brown trout condition was generally higher in clear lakes, Lake Wanaka fish were an exception. Trout depth distribution was positively related to depth of the littoral zone. Brown trout were caught at most depths whereas rainbow trout showed variable depth preferences in different lakes. Rainbow trout catch rate, weight, and condition factor were unrelated to differences in depth of the littoral zone or lake level fluctuations, and it was concluded that spawning success and limnetic food supplies may be more important for this species. Spawning interactions may account for the different species composition between the stable clear Lake Wanaka, and the adjacent fluctuating clear Lake Hawea. Moderate and slow lake level fluctuations appear to have limited effects on trout in clear lakes, probably because trout are able to use deep littoral habitat and food supplies.

Seasonal effect on lactate dehydrogenase and citrate synthase in snapper ( Pagrus auratus) - S. A. Majed; R. M. G. Wells; B. H. Mcardle (New Zealand Journal of Marine and Freshwater Research, 2002)
The activities of two enzymes involved in metabolic energy production, lactate dehydrogenase (LDH) and citrate synthase (CS), were determined in the white trunk musculature of snapper, Pagrus auratus (Bloch & Schneider 1801), to determine whether the metabolic capacity reflects seasonal variations. LDH and CS activities for a population of wild fish were monitored on a monthly basis over a period of 1 year and correlated with body length and seasonal variation. Significant correlations were observed between enzyme activity and body length. Increased LDH activity may reflect energy demand for anaerobic burst swimming. In contrast, declining CS activity with increasing body length may indicate a reduction in energy generation. The seasonal variation of CS activity coincided with the somatic growth cycle, increasing from 1.18 U g −1 white muscle in winter to 1.79 in spring and 1.78 in late summer, whereas LDH activity did not show a clear seasonal pattern. This information could be useful for tracking metabolic capacity in field specimens using simple biochemical analysis.

Surface run‐off from mineralised road aggregate, Puhipuhi, Northland, New Zealand - D. Craw; D. Chappell; A. Black (New Zealand Journal of Marine and Freshwater Research, 2002)
Roads in the Puhipuhi area of Northland, New Zealand, have been surfaced with road aggregate derived from hydrothermally mineralised rocks, which contain iron sulphides (pyrite and marcasite). Oxidation of the iron sulphides results in localised acidification, typically to pH 3, on roads and in source quarries. This low pH is at least one pH unit more acidic than typical background pH of 4–5.5 in forested areas through which the roads pass. Regional background pH is near neutral, and this may be in part an anthropogenic result of development of farmland in the Puhipuhi area. Lower natural pH is partly because of variable degrees of mineralisation of the underlying rocks on the 100 m scale. Arsenic (As) is the best metallic indicator of mineralisation, and mineralised rocks commonly have As contents between 100 and 1000 ppm above a regional background of 5–20 ppm (fresh greywacke) and 0.2–5 ppm (basalt and clay‐altered greywacke). Road aggregates have As between 20 and 200 ppm, locally lower than naturally mineralised rocks and soils. Mineralised rocks have 1–100 ppm mercury (Hg) above regional background of 0.1–0.25 ppm (fresh greywacke) and 0.04 to 0.14 ppm (basalt and clay‐altered greywacke). Soils have up to 10‐fold variation in As and Hg within the soil profile, with high metal levels in the C horizon associated with iron oxyhydroxides. Base metals, copper (Cu), lead (Pb), and zinc (Zn) are generally near to regional background throughout the Puhipuhi area, including road aggregates. Neither As nor Hg are significantly mobilised in solution in run‐off from road aggregate, but the low pH signature of road run‐off can be traced for c. 50 m into forest soil, or more than 300 m in clay‐based watercourses. Sediments carried with the road run‐off may release As and Hg if they are transported into higher pH environments such as major rivers or farmland. The chemical effects of road run‐off are likely to be less than those from the natural mineralised rock occurrences that underlie many parts of the Puhipuhi area.

Demersal fish assemblages along the continental shelf and upper slope of the east coast of the South Island, New Zealand - Michael P. Beentjes; Brian Bull; Rosie J. Hurst; Neil W. Bagley (New Zealand Journal of Marine and Freshwater Research, 2002)
Data collected during five winter and three summer research trawl surveys in Pegasus Bay and Canterbury Bight (10–400 m), east coast of the South Island, New Zealand, were used to identify demersal fish assemblages from hierarchical cluster analysis and non‐metric multidimensional scaling. The environmental variables—depth, latitude, season, water temperature, sediment type, sea surface condition, and sea colour—were examined to determine their relationship to fish assemblages using multivariate redundancy analysis. Patterns of species richness were examined and described. Catch rates were generally higher in summer than winter (21 of 28 species) and higher in south Canterbury Bight in the depth range 30–200 m. Preferred depth was greater in winter than summer (21 of 28 species). Species richness declined with depth in winter. Four main demersal species assemblages were identified (inner shelf, outer shelf, shelf break, and upper slope) with minor changes in membership between summer and winter mostly as a result of a change in species preferred depth. Depth was the primary variable influencing fish assemblages with secondary effects of latitude, sediment, and bottom temperature.

Bob McDowall—his contribution to New Zealand's freshwater fish - Don Jellyman (New Zealand Journal of Marine and Freshwater Research, 2002)

Editorial board (New Zealand Journal of Marine and Freshwater Research, 2002)

Habitat preferences of giant kokopu, Galaxias argenteus - Martin L. Bonnett; Julian R. E. Sykes (New Zealand Journal of Marine and Freshwater Research, 2002)
The giant kokopu (Galaxias argenteus (Gmelin 1789)) is endemic to New Zealand, and is regarded as threatened. A perceived decline of the species has been attributed mostly to the loss and degradation of its habitat. To determine habitat requirements, information from the New Zealand Freshwater Fisheries Database, and from field surveys in the South Island were analysed. These indicated that five habitat features are important: in‐stream cover, deep water, low water velocity, proximity to the sea, and overhead shade/riparian cover. These features were important in two distinct regions surveyed and for both juvenile and adult fish. The effects of different types of riparian and in‐stream cover were examined, but it appeared that the presence of some form of cover was more important than its composition. The conservation and management of giant kokopu will probably continue to be based upon management of their habitat, and these processes will be enhanced by the knowledge of the species’ habitat requirements.

Growth, survival, and recruitment of juvenile shortfinned eels ( Anguilla australis) in a large New Zealand coastal lake - Eric Graynoth; Donald J. Jellyman (New Zealand Journal of Marine and Freshwater Research, 2002)
Annual changes in the size composition and relative abundance of juvenile shortfinned eels ( Anguilla australis Richardson) in Lake Ellesmere, New Zealand, were studied. Juveniles ( −1 (range 6.3–22.9 mm year −1 ), and are probably limited by the lack of food. Juvenile eels had high survival rates, exceeding 0.80 year −1 and were probably close to 1.0 year −1 . Recruitment into this shallow, turbid, brackish lake was variable and was correlated with the duration and timing of the lake's opening to the sea. The decline in growth rates and restricted recruitment in recent years could reduce commercial catches of migrating silver eels for the next 10–15 years.

Spatial and temporal variability in length of glass eels ( Anguilla spp.) in New Zealand - B. L. Chisnall; D. J. Jellyman; M. L. Bonnett; J. R. Sykes (New Zealand Journal of Marine and Freshwater Research, 2002)
The spatial and temporal trends in length and pigmentation of glass eels for the shortfinned eel (Anguilla australis (Richardson)) and the longfinned eel (A. dieffenbachii (Gray)), were investigated by electric‐fishing 13 New Zealand streams/rivers on both the east and west coasts, at 14‐day intervals between July and December, from 1995 to 1998. A total of 11 479 glass eels were individually identified, measured, and assigned a pigmentation stage. On the basis of pigmentation, 67% were described as “newly arrived”. Modal pigmentation stage advanced over the arrival season for both species, and on arrival, longfinned glass eels were usually more pigmented than shortfinned glass eels. For any given time, North Island glass eels were consistently more advanced in pigmentation than were their South Island counterparts. Few very early pigmentation stages were recorded from the North Island samples, probably because sample sites were above estuaries and harbours. Longfinned glass eels were generally longer than shortfinned glass eels from the same river. Length of both species declined during the arrival season. Regional differences in mean length provides some indication of arrival patterns—predominantly from the north in an anti‐clockwise dispersal around New Zealand. Recruitment also showed annual variation, which appeared to be influenced by the El Niño Southern Oscillation, with the arrival route appearing to be more strongly from the north‐west during the El Niño phase (persistent westerlies) and from the north‐east during the La Niño phase (more persistent north‐easterlies). The mean length of new arrivals increased in the north and in the south‐west between 1995 and 1997, and decreased in all regions between 1997 and 1998, which could have been the result of changes in the duration of migration. Possible reasons for this include spatial and temporal changes to spawning, and oceanic variations in production.

Effects of deposited sediment on invertebrate drift: An experimental study - Alastair M. Suren; Ian G. Jowett (New Zealand Journal of Marine and Freshwater Research, 2001)
The effect of deposited sediment on invertebrate drift was experimentally assessed by adding fine sediment to three of six cobble‐lined artificial channels. One invertebrate species, Deleatidium spp., was added to the channel after the addition of sediment, whereas other taxa had colonised the channel naturally before the addition of sediment. Invertebrate drift was collected from each channel after the added sediment had worked its way into the interstitial spaces of the cobbles. Drift was collected every evening and morning for 3 days, after which time benthic densities in the channels were assessed. The percentage of benthos in the drift was significantly higher from sediment‐treated channels than from untreated channels for Paracalliope fluviatilis, Oxyethira albiceps, Hydrobiosis sp., and chironomid larvae. Drift of these animals from sediment‐treated channels was more than double that from untreated channels, with an average of over 5% of the benthos drifting from the sediment‐treated channels per day. Although there was no difference in the percentage of Deleatidium in the benthos that drifted from treated or untreated channels, significantly more individuals drifted from treated channels. Deposition of fine sediment had no significant effect on chironomid emergence or diurnal drift patterns for the taxa in the experiment. Periphyton communities in sediment‐treated channels were characterised by reduced chlorophyll a and increased inorganic content. We could not determine whether increased drift caused by deposited sediment reflected decreases in suitable habitat, reductions in food quality of the algae, or both.

Anatomical and ultrastructural comparison of the eyes of two species of aquatic, pulmonate gastropods: The bioluminescent Latia neritoides and the non‐luminescent Ancylus fluviatilis - V. Benno Meyer‐Rochow; Marina V. Bobkova (New Zealand Journal of Marine and Freshwater Research, 2001)
Light‐adapted eyes of two freshwater gastropods with similar habitat preferences ( Latia neritoides (Gray 1850) and Ancylus fluviatilis (Müller 1774)) were compared with each other in relation to optics, anatomy, and ultrastructure. Individuals of L. neritoides not only possess significantly larger eyes than similarly sized A. fluviatilis , they also have a more voluminous layer of photorecep‐tive membranes and appear capable of discerning at least some crude shapes. The eye of A. fluviatilis , on the other hand, has a very shallow retina which is so closely apposed to the lens that it can be little more than an indicator of light and darkness. Both types of eye are generously endowed with screening pigment granules and exhibit no signs of light‐induced damage. Although the lenticular F‐values for L. neritoides (1.78) and A. fluviatilis (1.74) alone are hardly indicative of an adaptation to a dark environment, the greater amount of photic vesicles and the substantial development of muscle fibres in the eye of L. neritoides suggest that the latter can adjust its vision more rapidly to changing light levels than that of A. fluviatilis . Since L. neritoides (but not A. fluviatilis ) has the ability to secrete a bright green luminescent mucus, a faster accommodation system would serve the species well. There is, however, no proof that in Latia bioluminescence alone has been responsible for the development of a more capable eye. Most of the differences between the eyes of L. neritoides and A. fluviatilis can be explained by the distinctly greater nocturnal activity of L. neritoides in combination with the ability to produce bright light in the latter species.

Growth rates of five species of surf clams on a southern North Island beach, New Zealand - H. John Cranfield; Keith P. Michael (New Zealand Journal of Marine and Freshwater Research, 2001)
Growth rates of five species of surf clam were estimated on the Kapiti Coast, southern North Island, New Zealand. Length‐frequencies of sequential population samples were analysed by the computer program, MULTIFAN. Incremental growth of marked individuals was analysed by the computer program, GROTAG. The von Bertalanffy growth parameters k and L 8 estimated by MULTIFAN for Spisula aequilatera (Deshayes in Reeve, 1854) were 0.80 yr −1 and 52.1 mm; for Mactra murchisoni Deshayes in Reeve, 1854 were 0.60 yr −1 and 72.3 mm; and for M. discors Gray, 1837 were 0.35 yr −1 and 60.1 mm. MULTIFAN could not model growth of Paphies donacina (Spengler, 1793) and Dosinia anus (Philippi, 1848) from the population samples. The growth parameters estimated by GROTAG for D. anus were 0.53 yr −1 and 53.0 mm and for M. murchisoni 1.84 yr −1 and 72.4 mm. The growth rates of P. donacina, S. aequilatera , and M. discors were estimated for the size range of their incremental growth data and the estimates are usable for this limited size range only. Growth rates of each species varied with depth in the surf zone in the same way in the North and the South Island. The growth rate of two species was faster in the South Island and asymptotic size of all species was greater in the South Island.

Effects of sea urchin (Evechinus chloroticus) grazing in Dusky Sound, Fiordland, New Zealand - E. Villouta; W. L. Chadderton; C. W. Pugsley; C. H. Hay (New Zealand Journal of Marine and Freshwater Research, 2001)
Evechinus chloroticus (Val.) is known to be an important grazer of subtidal barren habitats in northern New Zealand but its role in structuring rocky reef communities at colder southern localities is poorly understood. The present study was prompted by a proposal for the establishment of an E. chloroticus fishery in Dusky Sound, Fiordland, New Zealand. To determine the ecological importance of E. chloroticus in Dusky Sound, sea urchins were experimentally removed from shallow fucoid fringe (upper zone), mid‐depth barrens (middle zone), and deeper algal meadow (lower zone), at eight sites and compared with a paired set of eight control sites. Two years of continuous removal of E. chloroticus resulted in conspicuous changes to the algal community at all depth zones examined. The density of fucoid algae (Carpophyllum spp., Sargassum spp., Cystophora spp., and Landsburgia quercifolia) increased mostly in the upper and middle zones, although smaller increases were also observed in the lower zone. Changes in cover of herbaceous, turfing and crustose algae observed in the middle and lower zones were larger than in the upper zone. Density increases of the kelp Ecklonia radiata were observed mainly in the lower zone, although still important in the middle zone. These results show that E. chloroticus can have a strong influence on the structure of algal assemblages in Dusky Sound hence the development of an E. chloroticus fishery in this area should be treated with caution.

Sedimentation, suspension, and resuspension in Tasman Bay and Beatrix Bay, New Zealand, two contrasting coastal environments which thermally stratify in summer - Max M. Gibbs (New Zealand Journal of Marine and Freshwater Research, 2001)
The influence of density stratification on sedimentation, suspension, and resuspension in Tasman Bay and Beatrix Bay, New Zealand, two contrasting coastal environments, was studied with specific reference to the implications for modelling aquaculture sustainability. Tasman Bay, an enhanced scallop (Pecten novaezelandiae Reeve) fishery, is a very large coastal indentation gently shelving to c. 20 m deep c. 10 km from shore and open to the Tasman Sea, whereas Beatrix Bay, an area of intense Greenshell™ mussel (Perna canaliculus Gmelin) aquaculture, is a small (22 km 2 × 30–40 m deep) enclosed embayment off the side of the nearby Pelorus Sound. Sediment trap arrays were used to determine the vertical fluxes of suspended solids and the associated chlorophyll component. Benthic chambers were used to investigate sediment nutrient regeneration. In summer, salinity gradients in both bays are minimal or non‐existent because of low inputs of fresh water and density stratification is mainly controlled by water temperature. The data from mid summer exhibited different spatial distribution patterns for detritus and phytoplankton biomass (as indicated by chlorophyll) in these two very different bays, although they had similar turbulent environments. The density discontinuity at the thermocline had a strong influence on settling of phytoplankton. There was evidence of upwards entrainment of suspended paniculate matter into the upper water column from the thermocline in Beatrix Bay. Benthic resuspension was estimated to contribute up to 90% of the suspended solids caught in sediment traps near the sea floor in both bays. The trapping rate of phytoplankton was thought to be dependent on species dominance. Possible mechanisms of resuspension included turbulence in the benthic boundary layer, and high velocities below the thermocline associated with internal seiches. The presence of a mid water column chlorophyll maximum in Beatrix Bay is discussed in terms of nutrient and light regimes at the thermocline, and species composition. In Tasman Bay, the chlorophyll maximum was thought to be caused by resuspension of benthic microphytes and their subsequent confinement in a thin layer (2–4 m thick) of high turbulence between the thermocline and the seabed.

Postulated responses of phytoplankton and bacteria to predicted increases of inorganic suspended sediments in oligotrophic lakes - Marc Schallenberg; Udo Friedrich; Carolyn W. Burns (New Zealand Journal of Marine and Freshwater Research, 2001)
We establish the relationships between concentrations of inorganic suspended sediments (ISS) on light, nutrients, phytoplankton, and bacteria in three oligotrophic lakes (four sites) and we use these relationships to predict the impacts of increasing concentrations of ISS on the biomass and productivity of phytoplankton and bacteria in the lakes. Increased concentrations of ISS contributed little available nutrient to the lakes. The relationships between ISS and underwater light attenuation differed among lakes because of variation in sediment size‐structure, and composition. Only at the site with the highest ISS concentrations and a relatively deep mixing depth, were phytoplankton apparently light‐limited and, thus, predicted to decline with increased ISS concentrations. In contrast to previously published studies, bacterial abundance and production were not highly correlated to suspended sediment concentrations in these lakes. However, bacterial biomass, productivity, and specific productivity were more strongly correlated to phytoplankton production. As a result of light limitation and stimulation of bacterial production, increases in ISS concentrations are not predicted to significantly shift the metabolic balance in the planktonic ecosystem of three of the sites towards greater heterotrophy. Where light limits phytoplankton production, increases in ISS are predicted to reduce the productivity of both phytoplankton and bacteria by direct inhibition of phytoplankton production, again without a large shift towards greater importance of the microbial loop. By reducing phytoplankton production and inhibiting larger cladoceran grazers, we predict that high concentrations of ISS will reduce available energy and its flow up the food chain.

Spatial variations in the levels of nutrients, chlorophyll a, and dissolved oxygen in summer and winter in Doubtful Sound, New Zealand - Barrie M. Peake; David J. Walls; Mark T. Gibbs (New Zealand Journal of Marine and Freshwater Research, 2001)
The influence of a strong surface low‐salinity‐layer (LSL) on the distribution of macro‐nutrients, chlorophyll a , and dissolved oxygen in a fiord was investigated in February and August 1994 in Doubtful Sound, New Zealand. Phosphate and nitrate levels were significantly lower in the LSL than in the underlying saline layer (SL) and increased with depth towards the open ocean suggesting exchange of open ocean water across the deep fiord sill and then vertical mixing with the LSL. Nitrate/phosphate ratios in the range 12.3–16.5 (summer) and 14.9–17.4 (winter) for the LSL compared with 9–10 for the SL for both seasons, may reflect significant differences in phytoplankton species and/or nitrogen cycling between the layers. Elevated silicate levels in the LSL decreasing towards the open ocean were attributed to conservative mixing of the freshwater discharge from the Tail Race with the SL. Biomass (chlorophyll a ) in the LSL was quite low even in summer and generally increased towards the open ocean but exhibited several local surface maxima perhaps related to variable zooplankton grazing and/ or light levels. Levels of dissolved oxygen were above saturation in the LSL and decreased with depth, but never to anoxic levels.

Prey spectrum of breeding sooty shearwaters ( Puffinus griseus ) in New Zealand - J. B. Cruz; C. Lalas; J. B. Jillett; J. C. Kitson; P. O'B. Lyver; M. Imber; J. E. Newman; H. Moller (New Zealand Journal of Marine and Freshwater Research, 2001)
Prey remains from sooty shearwater ( Puffinus griseus Gmelin, 1792) regurgitates, stomachs, and gizzards, were collected from four breeding colonies in southern New Zealand. We found a wide range of prey species (minimum 39 species of 35 genera), the most important of which were crustaceans (particularly euphausiid krill and hyperiid amphipods), cephalopods (notably arrow squid), fishes, and salps. Malacostracans (krill, amphipods, and decapods) were the predominant taxa of prey in both diversity and frequency of occurrence. Regurgitates were easily obtained from harvested chicks and provided the greatest range of prey remains (36 of the 39 species identified). However, these regurgitates comprised only 29% of the total number of samples collected. Fish, malacostracan, and salp prey ranged from 4 to 170 mm in size, whereas total lengths of squid ranged from 50 to 535 mm. Based on size and mass, the largest squid were undoubtedly scavenged, possibly in association with commercial fishers. The geographical distribution of prey species indicate that most sooty shearwaters breeding near Stewart Island forage in waters lying between the Subtropical and Polar Fronts. Our results suggest that the abundance of krill, the impact of fisheries and the influence of climate perturbations on prey species may play important roles in sooty shearwater breeding and survival.

Population dynamics and chemical ecology of New Zealand Demospongiae Latrunculia sp. nov. and Polymastia croceus (Poecilosclerida: Latrunculiidae: Polymastiidae) - Alan R. Duckworth; Christopher N. Battershill (New Zealand Journal of Marine and Freshwater Research, 2001)
For 3 years aspects of the population dynamics, growth, and bioactivity (measure of biologically active metabolite biosynthesis) of the Demospongiae Latrunculia sp. nov. and Polymastia croceus (Kelly‐Borges & Bergquist) were examined on a subtidal reef on the Wellington south coast, New Zealand. For both species, survival of adult sponges was high in all seasons, whereas juvenile sponges had poor survival. Recruitment of Latrunculia sp. nov. occurred in all seasons indicating that this species is reproductively active throughout the year. P. croceus recruited mostly in autumn, supporting previous work that found the sponge to be reproductively active in summer and early autumn only. For both sponge species, growth rates varied greatly between individuals and were unaffected by initial sponge size within the range examined. Sponges generally grew during winter and spring as the water temperature rose, and shrank during summer and autumn as the water temperature fell. This growth pattern may relate to seasonal variation in food abundance, and for P. croceus it may result also from seasonal differences in reproductive investment. After 2 years, Latrunculia sp. nov. and P. croceus had on average, halved and doubled in size, respectively. Latrunculia sp. nov. showed a seasonal pattern of bioactivity, being most active in spring possibly to prevent the surface overgrowth of fouling organisms. P. croceus had no seasonal pattern of bioactivity, but individuals were either very active or inactive. The bioactive metabolites in both species possibly aid in competitive interactions and prevent predation and biofouling.

Sedimentation of phosphorus fractions and temporal variation in the C:P ratio in La Concepción reservoir, southern Spain - Roberto García‐Ruiz; Gema Parra; Francisco Guerrero; Juan Lucena (New Zealand Journal of Marine and Freshwater Research, 2001)
The settling flux and content of organic carbon (C), organic matter, and different phosphorus (P) fractions were measured fortnightly during a 6‐month stratified period (from early April to early November) with sediment traps located at five different depths in La Concepcion, a mesotrophic and P‐limited reservoir in southern Spain. Characterisation of P fractions in the collected material was performed by a sequential extraction procedure. Sedimentation rates exhibited a distinct seasonal pattern, that allowed us to differentiate three periods: (1) a biogenic sedimentation period (BS), in which the sedimentation rates and total suspended matter concentration were lowest and the result of material of autochthonous origin; (2) a calcium carbonate precipitation period (CCP), in which there were high calcium concentrations in the settling seston; and (3) a rainfall period (R), in which the highest sedimentation rates occurred. Organic C, organic matter, and organic P content were highest in the settling material during the BS period and lowest during the R period. However, during the R period, inorganic‐P sedimentation rates were highest and the major P fraction was apatite‐P. Total organic, and inorganic (Fe‐ and Al‐bound and apatite) P, increased substantially, whereas total and organic C decreased with depth in the material collected by sediment traps during the BS and CCP periods. Consequently, the total C:P (C t :P t ) and organic C:P (C org :P org ) ratios decreased significantly with increasing depth of sediment traps.

Two species of benthopelagic calanoid copepods of the genus Neoscolecithrix Canu, 1896 s.s. from New Zealand and the segregation of Cenognatha n. gen. - Janet M. Bradford‐Grieve (New Zealand Journal of Marine and Freshwater Research, 2001)
Two species of benthopelagic calanoid Copepoda, Neoscolecithrix cf. magna (Grice, 1972) and N. ornata n. sp., are described from the upper slope off North Cape, New Zealand. Neoscolecithrix ornata is distinguished from other species of Neoscolecithrix Canu, 1896 s.s. that have a female leg 5 terminal segment with 4 spines (2 terminal and 1 on each border) principally by the transverse row of long, fine spines on the female genital double somite; and by the more squat terminal segment of leg 5 (length/width ratio about 3.7). This is the second time Neoscolecithrix has been recorded from New Zealand. A new genus, Cenognatha n. gen., is distinguished from Neoscolecithrix principally because: rostrum short (bearing 2 filaments); mandibu‐lar gnathobase masticatory margin with slender dorsal spinulose seta; maxilla endite 1 with 5 well‐developed setae, endite 3 without brush‐like sensory seta, endopod usually with 3 long worm‐like sensory setae and 5 brush‐like setae; posterodistal border of basis of legs 1–3 without spines; distal segment of female leg 5 and its basis subequal in length; male leg 5 of similar lengths on both sides (styliform on right), endopod present at least on 1 side, 1‐segmented and spine‐like on right.

Larval stages, developmental ecology, and distribution of Scyllarus sp. Z (probably Scyllarus aoteanus Powell, 1949) (Decapoda: Scyllaridae) - W. Richard Webber; John D. Booth (New Zealand Journal of Marine and Freshwater Research, 2001)
Phyllosomata and nistos of Scyllarus sp. Z taken from plankton around and offshore northern New Zealand and in the Tasman Sea are presumed to be those of S. aoteanus Powell, 1949, the most common Scyllarus species in this area. The full larval and postlarval development of this species are described. Three features are characteristic of Scyllarus sp. Z phyllosomata; a dorsal crest on the cephalic shield, dorsal thoracic spines, and a forked telson in middle stages persisting as two prominent spines outreaching the telson posterior margin in the final stage. Scyllarus sp. Z's closest affinities are with a group of Scyllarus species whose phyllosomata have forked telsons in middle stages and medium to strong posterolateral telson spines in the final stage. The nisto is low in profile but distinctive in its armature. Too few Scyllarus sp. nistos have been described to suggest any group to which that of Scyllarus sp. Z can be assigned. The spatial and temporal distribution of the larvae and postlarvae of Scyllarus sp. Z are also described. Although early larval stages and postlarvae are found close to New Zealand, mid‐ and late‐stage larvae are widely distributed, some well beyond the known latitudinal range of the adults. There is probably an extended egg‐bearing and hatching period as early stage larvae are caught in most months. Variable rates of development of the larvae and/or delayed metamorphosis, are also possible.

Intertidal communities in Doubtful Sound, New Zealand: Changes over time - Michelle C. Boyle; John B. Jillett; Philip V. Mladenov (New Zealand Journal of Marine and Freshwater Research, 2001)
Intertidal communities of Doubtful Sound, New Zealand, were surveyed in 1995 to establish the extent of changes since they were first surveyed 30 years earlier, before the Manapouri power scheme was completed in 1969. This scheme resulted in more than a 3‐fold increase of freshwater inflow to Doubtful Sound, through a tailrace to Deep Cove. Thickness of the low salinity surface layer exceeded the tidal range and was greater at high than low contemporary volumes of tailrace inflow. Intertidal habitats were mostly steep shores of solid rock, little more than 2 m in vertical extent. Freshwater run‐off, groundwater seepage, and aspect to sun were all major factors affecting the intertidal communities. Algae and lichens dominated shore communities. Normally common invertebrates were scarce, especially molluscan grazers. Major changes since the early 1960s included almost total disappearance of Hormosira banksii and exclusion of many other species notably Apophloea lyallii and Elminius modestus to outer reaches of the Sound.

Macrobenthic polychaete assemblages of the continental shelf and upper slope off the west coast of the South Island, New Zealand - P. K. Probert; G. B. Read; S. L. Grove; A. A. Rowden (New Zealand Journal of Marine and Freshwater Research, 2001)
Polychaete assemblages are described from replicate box‐core samples collected in summer 1983 at 18 stations on the continental shelf and upper slope (28–943 m) off the west coast of the South Island, New Zealand, south‐eastern Tasman Sea (c. 41–43°S, 169–172°E). Three main station groupings were identified by multivariate analysis: (1) inner shelf sandy stations characterised by Prionospio australiensis, Aricidea (Acesta) sp., Magelona cf. dakini, Paraprionospio aff. pinnata, Aglaophamus sp., Heteromastus filiformis , and Magelona sp.; (2) middle to outer shelf muddy stations characterised by Levinsenia cf. gracilis, Prionospio australiensis, Paraprionospio coora, Aglaophamus verrilli , and Auchenoplax mesos; and (3) upper slope sandy mud or mud stations characterised by Prionospio ehlersi . A combination of water depth and sediment clay content provided the best correlation with the biotic pattern. Spionidae was the most abundant family (49% of polychaete individuals), which may reflect the scope for opportunistic species in a shelf environment characterised by a high input of terrigenous sediment and episodic upwelling.

Survey of historical New Zealand shellfish samples for accumulation of gymnodimine - David J. Stirling (New Zealand Journal of Marine and Freshwater Research, 2001)
In 1994 a major biotoxin event occurred along the east coast of the South Island, New Zealand. Gymnodimine, a unique bioactive spiroimine, was isolated and characterised from Foveaux Strait dredge oysters ( Tiostrea chilensis = Ostrea chilensis ) collected during this outbreak. This study reports the results of liquid chromatographic‐mass spectrometric analysis for gymnodimine in 217 samples from eight species of shellfish over the years 1993–99. Of these samples 155, covering six species of shellfish, contained detectable gymnodimine with a range in concentration from 14.8 to 23 400 μg/kg. Gymnodimine‐containing shellfish occurred at 37 of the 63 sites sampled from around New Zealand . This study demonstrates that accumulation of gymnodimine is not limited to T. chilensis and can occur in other shellfish species over much of New Zealand. Gymnodimine is a possible cause of the numerous historical biotoxin screen‐positive results.

DNA identification of Pacific bluefin tuna ( Thunnus orientalis ) in the New Zealand fishery - P. J. Smith; L. Griggs; S. Chow (New Zealand Journal of Marine and Freshwater Research, 2001)
Muscle samples were collected from 69 specimens identified as Pacific bluefin tuna ( Thunnus orientalis ) (Temminck and Schlegel, 1844) in the New Zealand Exclusive Economic Zone (EEZ) between 1990 and 2000. Identifications before 1996 were based on body size and colour of the caudal keel; later identifications were mostly based on the shape of abdominal cavity. The tissue samples were tested with a diagnostic mitochondrial DNA marker that distinguishes southern bluefin Thunnus maccoyii (Castelnau, 1872) and Pacific bluefin tuna T. orientalis; 59 specimens were confirmed as T. orientalis and 10 as T. maccoyii . Specimens recorded as Pacific bluefin tuna by the shape of the abdominal cavity were correctly identified as T. orientalis , and this character can be used to identify large specimens landed on tuna vessels. Some specimens recorded as Pacific bluefin tuna on the basis of colour and size were T. maccoyii; and early records of T. orientalis in New Zealand waters, based on these characters, are unreliable. Unusual colour patterns were reported in some specimens of T. orientalis but not T. maccoyii . The Pacific bluefin tuna T. orientalis accounted for less than 0.3% of the bluefin tuna catch in the New Zealand EEZ during the 1990s.

Effects of protandric sex change on radula, pedal morphology, and mobility in Crepidula fecunda (Gastropoda: Calyptraeidae) - O. R. Chaparro; S. V. Pereda; I. Bahamondes‐Rojas (New Zealand Journal of Marine and Freshwater Research, 2001)
Protandrism was confirmed in Crepidula fecunda Gallardo 1979 by histological analysis of the gonad. Individuals were classified as immature (12 mm or less in shell length), male (13–26 mm), intersex (25–28 mm), and female (over 26 mm). There was an evident loss of mobility with growth— large females became completely sessile. The presence of epithelial glands in mobile individuals was associated with the need for lubrication during crawling, whereas the proliferation of subepithelial glands in sessile females was associated with adhesion. Mobility of immature and male individuals was related to grazing activities on biofilms, and in males was also associated with copulation. Grazing activity of motile individuals was carried out so that the radula teeth did not come into direct contact with the substratum, but rather harvested the biofilm surface. Sessile females used the radula to rasp the area under their shells, thus cleaning the substratum in preparation for oviposition. Since this process required that the radula enter into direct contact with the substratum, it suffered abrasion of radular teeth and loss of radular denticles, producing important alterations in its appearance in mature females. A complex interaction was observed between size, mobility, histological changes in the foot, activity, and tooth‐wear of the radula, which have been related to the sessile habit, sex change, and the oviposition process in this species.

First record of the crocodile shark, Pseudocarcharias kamoharai (Chondrichthyes: Lamniformes), from New Zealand waters - Andrew L. Stewart (New Zealand Journal of Marine and Freshwater Research, 2001)
Commercial tuna longline fishing targeting bigeye tuna, Thunnus obesus (Lowe 1839), on the Three Kings Rise, northern New Zealand, resulted in the bycatch of a single specimen of a mature male crocodile shark, Pseudocarcharias kamoharai (Matsubara 1936). This is the first record for the New Zealand Exclusive Economic Zone, and a major southern range extension of the species in the Indo‐Pacific.

Staggered nested designs to identify hierarchical scales of variability - Russell G. Cole (New Zealand Journal of Marine and Freshwater Research, 2001)
Staggered nested sampling designs are virtually unknown in biology, but are widely used in manufacturing because they are highly efficient. I used a staggered nested design to address variation in the abundance of an intertidal clam Austrovenus stutchburyi (Gray) at four spatial scales. The scales were addressed by sampling cells containing five samples spaced at 50, 5, 0.5, and 0.05 m from one another. Estimates of variation from staggered nested designs can be made via ANOVA and principal component methods. ANOVA and principal component methods estimated roughly equal variability among those four spatial scales of abundance, and at all but the smallest scales variances were estimated very imprecisely. Staggered nested designs are highly efficient, applicable to any nested design, and deserve to be investigated more widely.

Age, growth, and sexual maturity of two New Zealand endemic skates, Dipturus nasutus and D. innominatus - Malcolm P. Francis; Caoimhghin Ó Maolagáin; Darren Stevens (New Zealand Journal of Marine and Freshwater Research, 2001)
Rough and smooth skates ( Dipturus nasutus (Banks 1841) and/), innominatus (Garrick & Paul 1974)) were aged by counting growth bands on X‐rays of thick sections of vertebral centra. Band counts were imprecise, but there was no between‐reader bias. Age estimates were not validated. The oldest rough skate was 9 years old, but few were more than 6 years old. Females may live longer than males. The combined sexes von Bertalanffy growth curve was L r = 91.3 (1 ‐ e −0.16 [ t + 1.20 ]). Half the males matured by c. 52 cm pelvic length (PL) and 4 years, and females by 59 cm PL and 6 years. The oldest smooth skate in the sample was 24 years, but longevity probably exceeds that. Females appear to live longer than males. The combined sexes von Bertalanffy growth curve was: L t = 150.5 (1 ‐ e −0.095[ t + 1.06] ). Half the males matured by c. 93 cm PL and 8 years, and females by 112 cm PL and 13 years. Smooth skate are late maturing and long‐lived relative to other skates, whereas rough skate are early maturing with a moderate life span.

Birth demographics of bottlenose dolphins, Tursiops truncatus , in Doubtful Sound, Fiordland, New Zealand—preliminary findings - Patti A. Haase; Karsten Schneider (New Zealand Journal of Marine and Freshwater Research, 2001)
Bottlenose dolphins ( Tursiops truncatus Montagu) in Doubtful Sound (45°30′S, 167°00′E), New Zealand, live at the southern extreme of the species’ worldwide range. Demographics of this population were observed from 1994 to 1999. Sixteen of 18 live births occurred from December to February. This is a short birthing period for bottlenose dolphins; populations in tropical regions calve during 10–12 months of the year. Nine calves were born to a population of 65 animals in 1999, a birth rate (13.8%) twice that of the average for 1995–97 (5.6%). Average calving interval during the observation period was 3 years (SD = 1.15) with a range of 2–5 years. Apparent survival rate of calves to Year 1 was 80.0%. Birth rate, calving interval, and mortality of calves are comparable to other bottlenose populations worldwide. Parturition appears to become strongly seasonal with increasing latitude in bottlenose dolphin populations.

Promising signs of regeneration of blue cod and oyster habitat changed by dredging in Foveaux Strait, southern New Zealand - H. John Cranfield; Glen Carbines; Keith P. Michael; Alistair Dunn; Dean R. Stotter; Darren J. Smith (New Zealand Journal of Marine and Freshwater Research, 2001)
Epifaunal reefs in Foveaux Strait are oyster (Ostrea chilensis Philippi, 1845) habitat. One hundred and thirty years of oyster dredging has diminished the complexity and distribution of these reefs. Commercial densities of blue cod (Parapercis colias (Forster in Bloch and Schneider, 1801)) were discovered on epifaunal reef habitat in 1989 and became the focus of a major blue cod fishery. We document habitat changes that followed the closing of the oyster fishery in 1993 and interactions between the blue cod and oyster fisheries after the oyster fishery was reopened in 1996. Evidence from blue cod fishers and oyster surveys suggests that the benthic habitat of some oyster beds regenerated in the absence of dredging and that the relative density of blue cod, and then oysters, rebuilt to commercial levels. Benthic habitat was modified once more when oyster dredging restarted and the relative density of blue cod on oyster beds fell again. The observations suggest that rotational fishing of oysters could mitigate the effects of dredging on habitat and that marine protected areas could expedite habitat recovery. Increasing habitat complexity and blue cod density on a reef of oyster shells formed by an oyster fisher suggests that habitat enhancement might remedy effects of dredging. The questions raised by the observations could be answered by management experiments on the scale of the fisheries.

Toxicity in benthic freshwater cyanobacteria (blue‐green algae): First observations in New Zealand - Keith D. Hamill (New Zealand Journal of Marine and Freshwater Research, 2001)
Toxic cyanobacteria have been linked to dog deaths in the Waikanae River (1998) and Mataura River (1999 and 2000), New Zealand. These were Oscillatoria‐ like species which formed benthic mats. This is the first time in New Zealand that animal deaths have been linked to toxins from benthic cyanobacteria.

Spatial and temporal variation in the abundance and composition of ichthyoplankton in a large South Island, New Zealand river estuary - Darin L. Sutherland; Gerard P. Closs (New Zealand Journal of Marine and Freshwater Research, 2001)
Larval and juvenile fish drifting on ebb tides were collected from early summer to mid autumn at various locations in the Taieri River and Waipori River estuary, South Island, New Zealand. A total of seven species of fish were recorded, however only three species were regularly collected. These were the larval common bully (Gobiomorphus cotidianus McDowall), larval inanga (Galaxias maculatus Jenyns), and postlarval cockabully (Tripterygion nigripenne Valenciennes). Common bully densities were highest in mid January, with the highest densities being recorded drifting out of Lake Waihola. Inanga densities were highest in March and April, with the highest densities being recorded in the channels draining wetland areas where extensive tidal inundation of riparian vegetation occurred. Cockabully were recorded from February to April, mostly at more downstream sites. Inland penetration by marine species was considerable, with two marine species, clingfish (Trachelochismus pinnulatus Forster) and smooth leatherjacket (Parika scaber Forster), being recorded c. 12 km upstream in late summer.

New Zealand fiords: Researching, managing, and conserving a unique ecosystem (New Zealand Journal of Marine and Freshwater Research, 2001)

Upper‐slope fish communities on the Chatham Rise, New Zealand, 1992–99 - B. Bull; M. E. Livingston; R. Hurst; N. Bagley (New Zealand Journal of Marine and Freshwater Research, 2001)
Catch rate data for fish species caught in 200–800 m depths during summer trawl surveys of the Chatham Rise to the east of New Zealand in 1992–99 were explored to assess community structure and species associations and to identify changes that occurred within the time series of surveys. The community was dominated by hoki ( Macruronus novaezelandiae Hector), a Southern Hemisphere merlucciid hake, which was more abundant than all other species combined and occurred at 97% of the 1048 trawl stations. Three groupings offish species were identified on the basis of descriptive and cluster analyses, associated with the 200–350, 350–550, and 550–800 m depth ranges. Redundancy analysis showed that depth, latitude, and to a lesser extent longitude explained most of the variation in abundance and composition of catches. Spatial patterns in species diversity and fish density were investigated. Trends within the time series show a significant decline in the biomass of hoki and changes in biomass of several other abundant species. However, there was little change in diversity, density, or division into groupings. The changes in abundance may be related to increased fishing activity and/or other factors such as changes in catchability because of the rising bottom temperatures observed during the surveys.

Feeding ecology of the banded wrasse Notolabrus fucicola (Labridae) in southern New Zealand: Prey items, seasonal differences, and ontogenetic variation - Christopher M. Denny; David R. Schiel (New Zealand Journal of Marine and Freshwater Research, 2001)
Notolabrus fucicola Richardson, a large common labrid inhabiting shallow waters around New Zealand and southern Australia, were collected monthly (December 1996‐February 1998) around Kaikoura on the east coast of the South Island, New Zealand. Their diet, temporal variation in prey and gut fullness, and ontogenetic differences were examined. N. fucicola is a generalist predator, the major prey items being bivalves, amphipods, and crabs, which varied temporally in their diet. There were size specific changes in their diet. Small fish (100–180 mm) ate mostly amphipods and isopods, whereas larger fish (> 180 mm) ate mainly bivalves, crabs, and gastropods. There was a temporal variation in gut fullness but no significant difference between sexes.

Wind‐wave development across a large shallow intertidal estuary: A case study of Manukau Harbour, New Zealand - Murray J. Smith; Craig L. Stevens; Richard M. Gorman; John A. McGregor; Cameron G. Neilson (New Zealand Journal of Marine and Freshwater Research, 2001)
Locally generated wind‐waves in estuaries play an important role in the sediment dynamics and the transport of biota. Wave growth in estuaries is complicated by tidally varying depth, fetch, and currents. Wave development was studied at six sites along a transect across Manukau Harbour, New Zealand, which is a large intertidal estuary with a tidal range of up to 4 m. Three meteorological masts were also deployed across the measurement transect to measure wave forcing by the wind. A spatial variation in wind speed by up to a factor of 2 was observed which has a significant effect on wave development at short fetches. The wind variation can be explained by the extreme change in surface roughness at the upwind land‐water boundary. The tidally varying depth results in non‐stationary wave development. At the long fetch sites wave development is dictated by the tidally varying depth with peak frequencies continuing to decrease after high water, whereas wave height is attenuated by bottom friction. The non‐dimensional energy and peak frequency parameters commonly used to describe wave growth, clearly exhibit depth limiting effects, but with wider scatter than in previous studies in simpler environments. The peak frequency predictions of Young & Verhagen (1996a) fit our data well. However, the wide variability of energy limits the usefulness of standard growth prediction curves in such situations, and highlights the requirement for a validated, shallow‐water numerical model.

Short‐term impacts of nutrients, Daphnia , and copepods on microbial food‐webs of an oligotrophic and eutrophic lake - Carolyn W. Burns; Marc Schallenberg (New Zealand Journal of Marine and Freshwater Research, 2001)
Metazooplankton are potentially important links between classical food chains and pelagic microbial food‐webs of lakes. We determined the short‐term effects of nutrient enrichment and predation on the microbial food‐webs of oligotrophic Lake Manapouri and eutrophic Lake Hayes, New Zealand, in summer, by adding calanoid copepods ( Boeckella hamata Brehm) and cladocerans ( Daphnia carinata King) to in situ enclosures in the presence and absence of added nutrients (nitrogen, phosphorus). In Lake Manapouri, bacteria and phytoplankton, but not picocyanobacteria, increased in response to nutrients; Daphnia reduced the densities of phytoplankton, bacteria, heterotrophic nanoflagellates (HNF), and ciliates; and Boeckella lowered the densities of HNF and ciliates. In Lake Hayes, the growth of bacteria, HNF, and phytoplankton, including eukaryotic picoautotrophs, was enhanced by enrichment; Daphnia depressed the concentrations of picoautotrophs and HNF, whereas Boeckella decreased the density of ciliates. In both lakes, Boeckella removed ciliates at higher rates per unit biomass than Daphnia . Our study provides clear evidence of stimulation and inhibition of pico‐plankton by nutrients, and of potential consumer‐mediated control of microbial food‐webs by crustacean zooplankton.

Measuring reproductive condition in the Greenshell™ mussel Perna canaliculus - S. Buchanan (New Zealand Journal of Marine and Freshwater Research, 2001)
The annual reproductive cycle of Perna canaliculus (Gmelin) was investigated for 1 year by collecting monthly gonad samples from an intertidal population. Gonads of 50 animals were dissected and photographically recorded on video before being fixed for histological sectioning. The histological gonad sections were examined both qualitatively, using a classification and scoring system (S) and quantitatively, using image analysis technology. The quantitative measures used were the proportion of: (1) sections comprising follicles (FC); (2) sections comprising gametes (GC); and (3) the proportion of follicles comprising gametes (G/F). Significant consecutive monthly changes in the qualitative and quantitative measures indicated major spawning events. Gametogenesis occurred during winter with a spawning in August‐September. Gonad condition remained low during the spring and early summer until a development period between January and March. A second major spawning event occurred between March and April. There was a high degree of synchrony in reproductive status observed between the sexes. When comparing the four measurement methods using the f statistic as an index of power the GC measure was found to be the most reliable. A gonad visual grading system was developed for rapid assessment of gonad reproductive status and tested. Visual grades of pre‐recorded gonad samples were compared to the histological measures. Increasing visual grade correlated strongly with increases in all of the histological measurements. The visual grading was a good predictor of the spawning activity of female P. canaliculus .

Factors controlling litter input dynamics in streams draining pasture, pine, and native forest catchments - M. R. Scarsbrook; J. M. Quinn; J. Halliday; R. Morse (New Zealand Journal of Marine and Freshwater Research, 2001)
The effects of varying land use on the inputs of litter to streams were investigated in nine small Waikato, New Zealand, hill country streams between June 1995 and October 1997. Mass, timing, and composition of both vertical and lateral litter inputs were measured. Litter inputs to pasture streams were lower than those to streams in native or exotic pine forest. Litter inputs to native forest streams peaked in summer, with leaf material forming the dominant litter‐type throughout the year. The pine forest sites showed a winter minimum, with a pulse of reproductive litter (pollen heads) in spring. One pasture site, where riparian vegetation included willow and poplar showed an autumnal peak, with low inputs at other times of the year. Climate variables (air temperature, rainfall, and windrun) varied in their power of prediction of litter inputs. Mean air temperature showed a strong positive relationship with monthly litter input at the most intensively sampled native forest site. Annual litter inputs were positively related to canopy cover, although canopy‐type modified this relationship. At several sites lateral inputs of litter showed a positive relationship with the slope of the contributing area. Overall, lateral inputs were positively related to % unvegetated groundcover. In open pastures the combination of a lack of riparian trees, and the potential litter‐trapping capacity of pasture grasses, severely limits inputs of coarse particulate organic matter to streams.

Effects of sampling frequency and laboratory detection limits on the determination of time series water quality trends - Brett Stansfield (New Zealand Journal of Marine and Freshwater Research, 2001)
Time series trend analysis using the non‐parametric seasonal Kendall Sen Slope estimator and the seasonal Kendall trend test was conducted on a water‐quality data set (raw and flow adjusted) from part of the Wellington Regional Council's freshwater baseline water quality monitoring programme. The trend analysis was conducted a number of times to determine what effects changing the sampling frequency and detection limit may have on the overall result of the analysis. Results indicate that trends detected using a low detection limit are often not detected when a higher limit is adopted. This holds for upward and downward trends. Results also indicate that if the sampling frequency was changed from monthly to quarterly fewer trends were detected. The results also show that where the quarterly data shows a trend it is usually of a slightly different magnitude (slope) compared with the monthly data. This paper serves to illustrate the importance of considering detection limits of variables and sampling frequencies for state of the environment monitoring programmes.

Links between climate variation and year class strength of New Zealand hoki (Macruronus novaezelandiae) : An update - B. Bull; M. E. Livingston (New Zealand Journal of Marine and Freshwater Research, 2001)
Hoki (Macruronus novaezelandiae Hector) year class strength (YCS) varies substantially from year to year. We examined associations between YCS and climate variables including the Southern Oscillation Index (SOI), satellite sea surface temperatures (SSTs), synoptic weather patterns, wind speeds, and the depth of the west coast, South Island, New Zealand, mixed layer. We evaluated the predictions of a model developed 2 years ago to predict YCS of the western and eastern New Zealand hoki stocks from similar climate variables. New predictive models were developed using updated data. Strong year classes of the western hoki stock were associated with cooler SSTs, a negative SOI, and westerly or south‐westerly flow along the west coast of the South Island. We accordingly predict a moderately strong 1997 year class and weak 1998 and 1999 year classes for the western stock of hoki. The current model cannot predict eastern stock year class strengths with confidence.

Fiordland is a special place - Clive D. Roberts (New Zealand Journal of Marine and Freshwater Research, 2001)

Diel variation in spawning orange roughy (Hoplostethus atlanticus , Trachichthyidae) abundance over a seamount feature on the north‐west Chatham Rise - B. Bull; I. Doonan; D. Tracey; A. Hart (New Zealand Journal of Marine and Freshwater Research, 2001)
The diel variation in abundance of an orange roughy ( Hoplostethus atlanticus Collett) spawning aggregation on a deepsea seamount on the Chatham Rise known as “Graveyard” was studied using acoustics. A 4‐day survey was carried out using a Latin cube statistical design. The acoustic data was echo‐integrated and analysis of variance was carried out to estimate the effects of day, time of day, and transect path. The estimated biomass of the spawning aggregation did not display any significant diel variation. We conclude that this result validates the current practice of acoustically surveying orange roughy on this seamount without considering diel effects. The aggregation fluctuated in abundance over the survey period, suggesting that turnover offish was occurring. Differences in roughy biomass with transect orientation indicate the importance of randomised radial transects for these surveys.

Avoidance behaviour of freshwater fish and shrimp exposed to ammonia and low dissolved oxygen separately and in combination - Jody Richardson; Erica K. Williams; Christopher W. Hickey (New Zealand Journal of Marine and Freshwater Research, 2001)
The responses of common smelt ( Retropinna retropinna Richardson), inanga ( Galaxias maculatus Jenyns), common bully ( Gobiomorphus cotidianus McDowall), and shrimp ( Paratya curvirostris Heller) to ammonia and low dissolved oxygen (DO), separately and in combination, were measured in a fluvarium. Only common smelt avoided high or low ammonia (c. 8.5 and 2.0 g m −3 NH3, respectively) and low DO (c. 2 g m −3 ) alone and in combination. Shrimp avoided high ammonia and low DO+ammonia but not low DO on its own. Inanga and bullies showed no significant negative response to either contaminant; rather, inanga were strongly attracted to low ammonia and bullies to low DO. These results parallel those from toxicity experiments that show common smelt and shrimp are usually among the most sensitive native species to various contaminants. The consistent and appropriate avoidance behaviour shown by common smelt, in particular, suggests this species would be a good indicator organism for assessing the health of lowland waterways.

Partitioning of metals (Fe, Pb, Cu, Zn) in urban run‐off from the Kaikorai Valley, Dunedin, New Zealand - Luke M. Mosley; Barrie M. Peake (New Zealand Journal of Marine and Freshwater Research, 2001)
Urban run‐off from a catchment in Dunedin, New Zealand was sampled and chemically characterised (iron (Fe), lead (Pb), copper (Cu), zinc (Zn) in total and 0.4 μm) and their concentrations increased significantly at the beginning of storm run‐off. In contrast, the majority of Cu and Zn was found in the 0.4 μm fraction. The results indicate that Cu and Zn may be more bio‐available, and more difficult to remove by storm‐water treatment, than Pb. The pH level and the concentration of major ions (Ca +2 , Na + , Mg +2 , K + ), dissolved reactive phosphorus, and nitrate generally decreased during storm flows as a result of dilution by rainwater. Concentrations of total N and P often increased during the initial period of storm run‐off, which was likely because of wash‐off of particulate plant material.

Seasonal changes in ovarian activity of New Zealand turbot (Colistium nudipinnis) and brill (C. guntheri) - C. W. Poortenaar; R. W. Hickman; M. J. Tait; F. M. Giambartolomei (New Zealand Journal of Marine and Freshwater Research, 2001)
Seasonal changes in ovarian activity were investigated in New Zealand turbot Colistium nudipinnis (Waite 1910) and brill Colistium guntheri (Hutton 1873), collected by commercial trawlers along the west coast of the South Island of New Zealand. Both species demonstrated group synchronous oocyte development, with a capacity for multiple ovulations within a reproductive season. During a 17‐h trawl survey, ovulated turbot were caught between 1500 and 2030 h, indicating a daily spawning rhythm. The turbot and brill spawning seasons were prolonged (late autumn to mid summer). A protracted spawning season confers some advantages in aquaculture.

Folklore and chimerical numbers: Review of a millennium of interaction between fur seals and humans in the New Zealand region - Chris Lalas; Corey J. A. Bradshaw (New Zealand Journal of Marine and Freshwater Research, 2001)
The increase in numbers and range expansion of New Zealand fur seals ( Arctocephalus forsteri Lesson) in the New Zealand region has prompted many people to comment on their effects on the marine and coastal environments. Overall there are anomalies in the data describing the distribution and abundance of fur seals in the New Zealand region, and there is a need for a better understanding of the interactions with humans and the impacts on the New Zealand environment. The distribution resulting from the present pattern of re‐colonisation differs from the perception of their distribution before decimation by humans. We hypothesise that the pristine distribution was temperate rather than subantarctic. Previously published records which have documented changes in the abundance and distribution of the species are shown to be wanting. The most controversial management issue is interaction with commercial fisheries where we conclude that neither of the extreme options, culling of seals nor closure of some fishing grounds, is justified. Other issues addressed include tourism, te tikanga Maori o mahinga kai (the customary use of wildlife by Maori), and impact of fur seals on the coastal environment. This species offers a rare and exciting opportunity to test the theoretical processes of population expansion that can be investigated as a natural experiment. We suggest that the current management policy should remain unchanged until the current paucity of information on the degree of interaction between fur seals and humans has been addressed.

Ocean tides around New Zealand - Roy A. Walters; Derek G. Goring; Rob G. Bell (New Zealand Journal of Marine and Freshwater Research, 2001)
The distribution of amplitude and phase for eight ocean tidal constituents (M 2 , S 2 , N 2 , K 2 , K 1 , O 1 , P 1 , Q 1 ) is presented as tidal maps for the New Zealand area. The distribution was calculated using a barotropic tidal model driven by TOPEX/ Poseidon data on the outer ocean boundaries. The maps exhibit the known features of the tides in this area such as a complete rotation of the semi‐diurnal tides around New Zealand and the reduced spring‐neap variations on the east coast. They also point out several new features for which there are few or no observations, such as diurnal trapped waves and shelf waves. A comparison of the model results with observations shows that sea level errors are within 0.1 m in amplitude and 10° in phase for the largest constituents at all locations, including sites where the data are of low quality and where the geometry is not adequately resolved. For locations where the geometry is adequately represented and the observations are of high quality, sea level errors are within 0.02 m in amplitude and 7° in phase. These results represent the most accurate and highest resolution calculations of tides and currents yet attained for this area.

Diet composition and guild structure of mesopelagic and bathypelagic fishes near Macquarie Island, Australia - A. C. Gaskett; C. Bulman; X. He; S. D. Goldsworthy (New Zealand Journal of Marine and Freshwater Research, 2001)
Mesopelagic (200–1000 m) and bathypelagic (> 1000 m) fish near Macquarie Island, Australia, are important in the diets of seals, seabirds, and Patagonian toothfish. They also form important links between the productivity at shallow and deeper water depths. Here we analyse the diets of 23 fish species, 13 of which are from the family Myctophidae from 254 stomach samples. Crustaceans (particularly copepods, amphipods, and euphausiids) were the dominant prey in 18 species. Fishes were the dominant prey in five species. Further analysis showed that five of the 13 myctophid fishes had a low level of similarity in diet composition between individuals of each species, whereas the other eight species had significantly high levels of similarity. Cluster analysis and randomisation procedures suggested the existence of five trophic guilds among the Myctophidae.

A new species of benthopelagic copepod of the genus Tharybis (Calanoida: Tharybidae) from the upper slope, north‐eastern New Zealand - Janet M. Bradford‐Grieve (New Zealand Journal of Marine and Freshwater Research, 2001)
A new species of benthopelagic calanoid Copepoda is described from off North Cape, New Zealand. The species, Tharybis inaequalis n. sp. (Family: Tharybidae), is the first record of this genus from New Zealand. T. inaequalis females are distinguished from all other described Tharybis by the asymmetrical fifth legs (long and thin on the left and short and squat on the right) with a pair of subequal outer terminal spines and an inner articulated terminal spine that is about 1.5 times the length of the outer spines. Males are most like those of T. compacta and T. minor but the inner lobe on right leg 5 segment 3 is small and rounded and entirely directed into the midline; the left leg 5 exopod segment 3 also has several distal lamellae and in inner proximal spine. As in T. minor , male antennule segments XXII and XXIII are separate on the left and fused on the right.

Evidence for long‐term site fidelity of snapper (Pagrus auratus) within a marine reserve - Trevor J. Willis; Darren M. Parsons; Russ C. Babcock (New Zealand Journal of Marine and Freshwater Research, 2001)
Increases in the density of exploited species on unfished reefs logically implies that some individuals are at least temporarily resident, or show fidelity to a particular area. We tagged snapper ( Pagrus auratus (Bloch & Schneider 1801)) in the Leigh Marine Reserve, New Zealand using visible implant fluorescent elastomer tags, recoverable by diver visual sightings without the need to recapture the fish. Batch tagging of snapper ( n = 907) was done during an angling survey in June and December 1996, and individually coded tags were implanted by divers ( n = 117) in January 1999. Snapper tagged during both programmes were recovered on irregular intervals from 1997 to 2000. There were 71 recoveries of batch tags within 500 m of their tagging sites, and these recoveries were still being made >3 years after tagging: Of individually coded fish, 49 (42%) were seen, sometimes repeatedly over several months, close to their respective tagging sites. These observations included snapper as small as 23 cm fork length, contradicting the commonly held impression that only large snapper take up long‐term residency on reefs. This preliminary evidence suggests that some snapper exhibit site fidelity to areas only a few hundred metres wide, and in the absence of fishing may occupy the same area for years.

Age, growth, and commercial landings of yellowtail scad (Trachurus novaezelandiae) and blue mackerel (Scomber australasicus) off the coast of New South Wales, Australia - John Stewart; Douglas J. Ferrell (New Zealand Journal of Marine and Freshwater Research, 2001)
Size and age compositions of yellowtail scad ( Trachurus novaezelandiae Richardson 1843) and blue mackerel ( Scomber australasicus Cuvier 1832) were studied in the inshore purse‐seine fishery off the coast of New South Wales, Australia. Ages were assigned by counting annual marks in otoliths for both species. Sampling from two regions showed no geographical differences in the age compositions of catches for either species. The fishery for yellowtail scad was based on 2‐ and 3‐year‐old fish, but with significant numbers of fish up to 11 years. Seventy percent of the fishery for blue mackerel was based on fish aged 1 year, with the majority of the rest being in their first or third years. Maximum ages recorded in this study were 14 years for yellowtail scad and 7 years for blue mackerel. We found no major differences in the sizes of blue mackerel landed in either region sampled, but yellowtail scad were larger in the northern region than in the southern. Growth rates of blue mackerel were the same from both regions, but yellowtail scad sampled grew significantly faster in the northern region. The fishery for yellowtail scad off New South Wales is currently based on younger and smaller fish than other trachurid fisheries around the world. This, together with the observed spatial variation in growth and population structure, suggests that the fishery for yellowtail scad in New South Wales should be carefully monitored.

Patterns of abundance and population size structure of herbivorous fishes at the subtropical Kermadec Islands and in mainland New Zealand - Russell G. Cole (New Zealand Journal of Marine and Freshwater Research, 2001)
Patterns of abundance and population size structure for nominally herbivorous fishes were investigated at the subtropical Kermadec Islands in 1992 using both tape transect and timed‐count techniques. Timed counts were subsequently used to sample six localities in mainland New Zealand, including coastal offshore islands. Herbivorous fishes of all genera were most abundant in shallow water. Kermadec Islands had slightly greater species richness of herbivorous fishes than north‐eastern mainland New Zealand and abundances in timed‐transects also showed a clear decline from north to south, with the southern localities having extremely low abundances. Offshore island groups in northeastern New Zealand had assemblages that were dominated by one pomacentrid, and size‐frequency distributions that were dominated by one adult size class of that species, whereas size‐frequency distributions at mainland New Zealand and Kermadec Islands locations were platykurtic. At Leigh, herbivorous fishes were observed throughout the depth range sampled (0–15 m) but were much more common in shallow macroalgal‐dominated habitats. There were suggestive patterns of increasing size and decreasing abundance with increasing latitudes.

Effects of substrate and sedimentation on the abundance of upland bullies ( Gobiomorphus breviceps ) - I. G. Jowett; N. C. Boustead (New Zealand Journal of Marine and Freshwater Research, 2001)
Most indigenous New Zealand freshwater fish are benthic, and use substrate elements for shelter, cover, and nesting sites. Sedimentation can reduce the amount of interstitial space provided by the substrate, thus reducing the amount of available cover and potentially influencing fish abundance. To test the effects of sedimentation on fish density, upland bullies ( Gobiomorphus breviceps Stokell) were introduced into experimental channels with different substrate treatments. After an acclimatisation period, they were allowed to emigrate. The maximum fish density and relative habitat suitability was then determined by the number of fish remaining after 6 days. Bully numbers declined by over 50% after 6 days in the trials with no cover, whereas with 20 cobbles providing cover for 40 bullies, numbers reduced by only 10%. When sufficient fine sediment was added to fill the spaces under the cobbles, bully numbers reduced by more than 60%, regardless of the number of cobbles. However, when cobbles were raised above the fine sediment, the number of bullies remaining in the channels was similar to the number remaining with cobbles and no sediment. The overall effect of high levels of sedimentation on bully density was similar to that of providing no cover, with the effect diminishing as the level of sedimentation decreased.

Ocean temperature climate off North‐East New Zealand - Philip J. H. Sutton; Dean Roemmich (New Zealand Journal of Marine and Freshwater Research, 2001)
The ocean temperature field off the north‐east coast of New Zealand is studied to quantify the annual cycle and reveal the intra‐ and inter‐annual variability. The data used are repeat expendable bathythermograph (XBT) sections between Auckland and either Suva or Honolulu which have been collected quarterly since 1986. These sections give temperature measurements between the surface and 800 m and Auckland and 30°S from 1986 to August 1999. The mean and annual cycle are compared with those from the NOAA World Ocean Atlas (WOA98). The results are similar; however WOA98 lacks the horizontal resolution to fully discern the East Auckland Current and North Cape Eddy, while the XBT analysis lacks the temporal resolution to discern higher frequency intra‐annual signals. The temperature variability in the mixed layer is dominated by the annual cycle, which accounts for 80–90% of the variance. The amplitude of the annual cycle diminishes rapidly with depth, from 2.8°C at the surface, to c. 0.1°C at 180 m. The phase of the annual cycle is retarded with depth, with peak temperatures occurring in February at the surface and in June/July at 180 m. Removing the annual cycle from the time series reveals the more subtle inter‐ and intra‐annual variability. This variability is of the order of 1°C in the upper 50 m, decreasing to 0.3°C at 400–500 m. The surface layer was cold between 1991 and 1994 (c. 0.7°C cooler than average), and 0.7°C warmer than average in 1999. The deeper ocean shows a different signal, being up to 0.3°C cooler in 1990–92, 0.3°C warmer in 1998, and c. 0.2°C warmer than average in 1999. The inter‐annual mixed layer variability is highly correlated with the Southern Oscillation Index and also with inter‐annual terrestrial air temperature and wind measurements from northern New Zealand. In contrast, at higher intra‐annual frequencies, the mixed layer variability is not correlated with air and wind measurements. At these higher frequencies, the air temperature is better correlated with the sea surface temperature (SST) than with the bulk mixed layer temperature.

Erratum (New Zealand Journal of Marine and Freshwater Research, 2001)

Subantarctic oceanography around New Zealand: Preliminary results from an ongoing survey - Michele Morris; Basil Stanton; Helen Neil (New Zealand Journal of Marine and Freshwater Research, 2001)
An ongoing observational program focused on variability in the subantarctic currents and water masses around southern New Zealand was initiated in May 1998. This paper describes the preliminary results deduced from CTD (conductivity, temperature, depth) data collected during three hydrographic surveys, and moored current and temperature records between 1998 and 1999. An extensive archived data set has also been analysed to provide a hydrographic climatology of the region. The low‐frequency circulation within the subantarctic zone is described, revealing previously unreported flow features: persistent but weak anticyclonic and cyclonic circulations over the Campbell Plateau and a strong cyclonic flow around the western edge of the Bounty Trough. Flow within the Subantarctic Front (SAF) is strongly constrained by the New Zealand bathymetry; diverting to follow the south‐eastern flanks of the Campbell Plateau and crossing to the Bounty Plateau, before separating to join the basin‐scale circulation. The flow features deduced from recent data are consistent with the hydrographic climatology as well as mid‐depth float trajectories. Subantarctic Mode Water (SAMW) is observed year‐round over an extensive fraction of the subantarctic zone: along the equatorward side of the SAF, over the Campbell Plateau, and flowing within the cyclonic circulation around the Bounty Trough. There is a marked cooling and freshening of SAMW between the deep water along the western flanks of Campbell Plateau and waters further east, consistent with a blocking of the eastward flow carrying warm and salty SAMW by the plateau. Earlier ideas that a substantial volume of SAMW is formed over the Campbell Plateau by deep vertical mixing (Heath 1981) are not substantiated by our data, which include seasonal observations of the upper water column.

Estimating the East Auckland Current transport from model winds and the Island Rule - Basil R. Stanton (New Zealand Journal of Marine and Freshwater Research, 2001)
The Island Rule allows the wind‐driven ocean transport around New Zealand to be determined from wind stress over the South Pacific. The transport in the western boundary current can be derived from the difference between the island transport and the interior Sverdrup transport to the east. This method has been used to estimate the transport in the East Auckland Current (EAUC) using ECMWF and NCEP model wind‐stress data, which are compared with transports derived from TOPEX/Poseidon satellite altimetry and expendable bathythermograph (XBT) sections. The results suggest that the mean transport in the EAUC can be explained by the Sverdrup dynamics implicit in the model results. However the model estimates of interannual variability in the EAUC were generally unrealistic, and some of the reasons for this are examined and possible extensions to the model suggested.

Naturally low seston concentration and the net energy balance of the greenshell mussel ( Perna canaliculus ) at Island Bay, Cook Strait, New Zealand - Jonathan P. A. Gardner; Raymond J. Thompson (New Zealand Journal of Marine and Freshwater Research, 2001)
This paper describes an investigation of the physiological energetics of the New Zealand greenshell mussel, Perna canaliculus (Gmelin, 1791), which is aimed at determining if mussels are absent from many shores of Cook Strait as a consequence of a negative energy balance resulting from ambient low seston quantity and quality. Seston characteristics and mussel physiological functions were measured under ambient summer conditions at Island Bay, a site in Cook Strait. Estimates of total particulate matter (TPM in mg litre −1 ), particulate organic matter (POM in mg litre −1 ), and particulate organic carbon (POC in |ig litre −1 ) were low but of a similar magnitude to values reported for many comparable temperate regions. However, seston % organic matter (% OM) values were consistently low ( P. canaliculus , and as such probably play a major role in explaining the almost complete absence of mussels from many Cook Strait shores.

Differential UVB‐sensitivities of five New Zealand freshwater zooplankton species - Dirk Ludwig Wübben; Ekkehard Vareschi; Ian Hawes; Greg Bodeker (New Zealand Journal of Marine and Freshwater Research, 2001)
The ultraviolet (UV) sensitivity of five species of freshwater zooplankton (three Cladocera, two Copepoda) were investigated. The animals were exposed to varying levels of UV‐radiation in a sunshine‐simulator and the UV doses for 10 and 50% mortality (LD 10 , LD 50 ) were estimated using a dose‐response model. To place these doses in context they were compared with modelled clear‐sky surface UV irradiances in New Zealand. The cladocerans Daphnia carinata and Ceriodaphnia dubia were sensitive to levels of UVB irradiance of LD 10 = 18–25 kJ m −2 and LD 50 = 35–37 kJ m −2 . These sensitivities are consistent with published values for other cladocera. In contrast a third cladoceran, Bosmina meridionalis , exhibited no higher mortality over the full range of the cumulative UVB‐doses used (3–40 kJ m −2 ) than controls receiving no UV exposure. The copepod Boeckella delicata showed the highest UV‐sensitivity of all organisms tested (LD10 = 7 kJ m −2 , LD50 = 33 kJ m −2 ) whereas for Boeckella triarticulata , which was more heavily pigmented than B. delicata , no UV‐induced mortality was observed. Under natural conditions UV irradiances of up to 100 kJ m −2 day −1 can fall on the surface of New Zealand lakes. Although this is attenuated in natural waters, these data suggest that UVB irradiance may be a significant ecological variable to some zooplankton species.

Relationships between land use and stream invertebrate community structure in a South Island, New Zealand, coastal stream catchment - Matthew J. Hall; Gerard P. Closs; Ralph H. Riley (New Zealand Journal of Marine and Freshwater Research, 2001)
Macroinvertebrate community composition was compared across streams draining catchments dominated by either native bush, agricultural or urban land uses within the Water of Leith stream catchment near Dunedin, New Zealand. Land use was associated with differences in taxon richness and faunal composition of communities present in each stream. The mean abundance levels of Ephemeroptera, Plecoptera, and Trichoptera were highest in native bush catchments, and lowest in urban catchments. In contrast, the mean abundance of Oligochaeta exhibited the opposite pattern. Increasing dominance of the urban and agricultural streams by pollution tolerant taxa was reflected in the Macroinvertebrate Community Index and Quantitative Macroinvertebrate Community Index scores.

1998/99 national survey of pesticides in grdundwater using GCMS and ELISA - Murray E. Close; Michael R. Rosen (New Zealand Journal of Marine and Freshwater Research, 2001)
A total of 95 wells throughout New Zealand were sampled during summer 1998/99 and analysed for a range of pesticides using gas chroma‐tography‐mass spectroscopy (GCMS). Thirty‐three wells (35%) had pesticides including triazine metabolites detected, with 18 wells (19%) having two or more pesticides detected. Only one well (K38/ 0172) had pesticides detected at levels greater than the maximum acceptable value (MAV) for drinking water. There were 20 different pesticides detected, usually at very low concentrations, as well as two triazine metabolites. Fifty‐seven out of the 75 pesticide detections (76%) belonged to the triazine group, with only five of these (9%) being >1 mg m −3 and 74% of these being 3 . Three of the 18 non‐triazine pesticide detections (17%) were > 1 mg m −3 with all three detections being in Well K38/ 0172. About half (44%) of the non‐triazine pesticides were −3 . Apart from Well K38/0172, the highest levels of pesticides with respect to the MAV were seen for simazine and terbuthylazine, which were 16 and 44% of the MAV, respectively, with the remaining pesticides all below 4% of their MAV. This indicates that, although there were very low levels of pesticides present in 35% of the wells, there would be no significant health risk based on the pesticides analysed from drinking the groundwater investigated with the exception of Well K38/0172. There was a significant decrease in the detection limits for many pesticides for the 1998/99 survey compared to the two earlier surveys. When the detection limits for the earlier surveys were applied to the present survey there would have been a total of 10 wells out of the 95 sampled (11%) with pesticides detected. This compared with 7% of the 82 wells in 1990 and 13.6% of the 116 wells in 1994 with detectable pesticides, indicating that a similar percentage of wells have had detectable pesticides in each survey once correction for variable detection limits has been made. There was a significant difference between wells with and without pesticide detections for the following factors: wells with pesticide detections had shallower well screens, were screened nearer the water table, had lower pH values and higher nitrate levels. Samples for analysis using two enzyme‐linked immunosorbent assay (ELISA) atrazine test kits were collected at the same time as the other pesticide samples. The “normal” atrazine ELISA test kit only showed four positive detections, mainly because of a relatively high detection limit. The high sensitivity (HS) atrazine test kits detected pesticides in 20 of the 28 samples that were tested. Nineteen of the 20 detections had pesticide detections using GCMS, with the other eight samples having no pesticides detected using GCMS. The HS atrazine ELISA test kit appears to be a useful indicator of pesticide contamination for New Zealand groundwater systems at a relatively low level of detection. All the positive GCMS results that were tested gave positive test kit results and there was only one potential false positive result. This is probably because the majority of pesticides detected in groundwater in New Zealand are triazines, and the HS atrazine kit has cross reactivity with most triazines and related pesticides.

Biochemical‐genetic and meristic evidence that blue and copper moki (Teleostei: Latridae: Latridopsis ) are discrete species - P. J. Smith; C. D. Roberts; P. G. Benson (New Zealand Journal of Marine and Freshwater Research, 2001)
Specimens of blue moki Latridopsis ciliaris (Forster in Bloch & Schneider, 1801) from New Zealand were shown to differ from specimens of copper moki Latridopsis forsteri (Castelnau, 1872) using two genetic methods—allozymes and muscle proteins. Allozyme techniques revealed fixed differences between blue and copper moki at 4 out of 15 loci. There was a genetic distance of 0.31–0.34 between population samples of the two colour morphs. The two morphs were also distinguished by iso‐electric focusing of muscle proteins. Meristic characters, counted in the specimens studied with genetic markers, revealed diagnostic markers in tubed lateral line scales and scales in the lower transverse series. It is concluded that specimens of blue moki from New Zealand and copper moki from New Zealand and Tasmania are valid species.

Seasonal changes in plankton and nutrient dynamics and carbon flow in the pelagic zone of a large, glacial lake: Effects of suspended solids and physical mixing - Mark R. James; Marc Schallenberg; Mark Gall; Robert Smith (New Zealand Journal of Marine and Freshwater Research, 2001)
The abundance and distribution of phytoplankton and zooplankton were followed from January 1993 to March 1994 in Lake Coleridge, a deep oligotrophic alpine lake in the Canterbury high country of New Zealand. Our data suggest physical processes associated with deep mixing and inputs of suspended sediments combined to limit planktonic biomass, diversity, and determine vertical distribution. The lake was strongly stratified in summer with a surface mixed layer of 20 m gradually extending down to 100 m by May. Over 50 taxa of phytoplankton were recorded. Changes in vertical distribution of most planktonic groups coincided with changes in the depth of vertical mixing. Phytoplankton biomass increased through summer with a diatom‐dominated peak in autumn. Cell numbers however, peaked in spring and were dominated by small chlorophytes. Phytoplankton photosynthetic production was highest in autumn but specific growth rates were highest in summer as a result of greater light availability combined with warmer temperatures. We suggest that large inputs of suspended sediments and glacial silt, may have limited the spring phytoplankton peak which occurs in a number of other temperate lakes. Bacteria and pico‐phytoplankton biomass peaked in winter following the phytoplankton peak suggesting they were relying at least in part on scenescing phytoplankton cells for dissolved organic carbon. Diversity of ciliated protozoa was low (11 taxa), Cladocera were absent, and the only crustacean zooplankton found in significant numbers was Boeckella hamata . Ciliated protozoan abundance was low (maximum 4600 litre 1) and peaked in summer (January‐March). Copepod nauplii peaked in August and peaks in abundance of copepodites and adults followed in September and November‐January respectively. Only two generations occurred during the year. The peak in copepod biomass followed phytoplankton peaks but lagged 1–2 months probably as a result of slow growth rates and the time for response to phytoplankton peaks.

Hook up on snapper. By MarkKitteridge. Published in 2000 by Reed Publishing (NZ) Ltd, 39 Rawene Road, Private Bag 34 901, Birkenhead, Auckland 10, New Zealand (http://www.reed.co.nz). 127 p., limpbound. ISBN: 0–7900–0756–8. Price: NZ$29.95 (orders: info@reed.co.nz).Reed field guide to New Zealand freshwater fishes. By R. M.McDowall. Published in 2000 by Reed Publishing (NZ) Ltd, 39 Rawene Road, Private Bag 34 901, Birkenhead, Auckland 10, New Zealand (http://www.reed.co.nz). 224 p., hardback. ISBN: 0–78900–0725–8. Price: NZ$39.95 (orders: info@reed.co.nz). - Trevor J. Willis; Angus R. Mcintosh (New Zealand Journal of Marine and Freshwater Research, 2001)

Phytoplankton distributions around New Zealand derived from SeaWiFS remotely‐sensed ocean colour data - R. J. Murphy; M. H. Pinkerton; K. M. Richardson; J. M. Bradford‐Grieve; P. W. Boyd (New Zealand Journal of Marine and Freshwater Research, 2001)
Ocean colour data from the NASA Sea‐viewing Wide Field‐of‐view Sensor (SeaWiFS) was used to estimate chlorophyll a concentration around New Zealand on a monthly basis between September 1997 and May 2000. The performance of the SeaWiFS chlorophyll a algorithm (OC4v4) was investigated by comparing in situ measurements of the underwater light field with measurements of phytoplankton pigment concentration by High Performance Liquid Chromatography. The algorithm performed well for chlorophyll a concentrations below 0.6 mg m‐3 but overestimated by a factor of two or more at higher concentrations. The average chlorophyll a concentration for New Zealand Exclusive Economic Zone was calculated as an indication of the overall productivity of the region and varied between 0.26 and 0.43 mg m‐3 with no obvious relationship to the Southern Oscillation Index. New Zealand northern subtropical and Tasman Sea waters had a classical cycle of spring and autumn chlorophyll blooms consistent with production being co‐limited by nitrate and light. Subantarctic waters had a low‐magnitude annual cycle of chlorophyll abundance that peaked in early autumn, consistent with production being predominantly limited by a combination of iron and light. Chlorophyll was generally highest in the Subtropical Front where subtropical and subantarctic waters mix. A series of persistent warm‐core eddies along New Zealand's east coast was obvious in many images, manifest as regions of low chlorophyll concentration.

Radiocarbon age for estuarine shells from Lakelands, Lake Ellesmere (Te Waihora), New Zealand - Maree A. Hemmingsen (New Zealand Journal of Marine and Freshwater Research, 2001)
Shells of the estuarine species Mactra ovata from Lakelands, Lake Ellesmere, New Zealand give a 14C Radiocarbon age of 670 ± 67 B.P. Their occurrence presents a problem as currently Lake Ellesmere is a brackish lake, separated from the Pacific Ocean by Kaitorete Barrier, a mixed sand and gravel barrier. According to previous research this barrier has enclosed a water body behind it in the position of Lake Ellesmere for up to 8000 years. Since the mid Holocene, at least three fluctuations between lacustrine and estuarine conditions are thought to have occurred. These fluctuations are believed to be associated with the avulsion of the Waimakariri River, to and from Lake Ellesmere. This study adds to the previous research by providing a timeframe within which one of these estuarine events occurred.

Spawning pattern, length at maturity, and fecundity of the southern blue whiting ( Micromesistius australis ) in the south‐west Atlantic Ocean - M. Pajaro; G. J. Macchi (New Zealand Journal of Marine and Freshwater Research, 2001)
Southern blue whiting ( Micromesistius australis Norman, 1937) inhabits the waters of the Southern Hemisphere, and in the south‐west Atlantic Ocean is distributed over an area next to the Malvinas Islands. At present, this species is suffering over‐exploitation and its biomass has decreased drastically. The histological analysis of ovaries and the oocyte size frequency distribution of gravid females indicate that southern blue whiting is a batch spawner with determinate annual fecundity. The spawning season of M. australis in the south‐west Atlantic Ocean extends from August to October, with a main peak during September. Spawning females were recorded mainly in the waters south and south‐west of the Malvinas Islands, close to the 200 m isobath. Total fecundity of seven M. australis females ranged from 148 300 to 713 900 yolked oocytes (46–55 cm total length (TL)). The mean total fecundity was 477 700 (206 783 SD) oocytes for one 51 cm TL female. Mean relative fecundity was 706 (258 SD) oocytes per g female weight, ranging from 277 to 967. The percentage of sexually mature females for each total length class indicated 50% female maturity was reached at 37.8 cm. This value was similar to those reported for this species between 1980 and 1990.

Hatching of Boeckella hamata (Copepoda: Calanoida) resting eggs from sediments of a tidally influenced lake - Catherine J. Hall; Carolyn W. Burns (New Zealand Journal of Marine and Freshwater Research, 2001)
Boeckella hamata Brehm appears in the plankton of Lake Waihola, New Zealand, a tidally influenced lake, only at times of low salinity. To determine whether B. hamata hatches from resting eggs, allowing it to re‐colonise the lake after periods of higher salinity, sediments were analysed for the presence of eggs and incubated in the laboratory at 15°C. Copepod eggs at a density of 1.3 × 10 4 eggs m‐ 2 were recorded. Over a 4‐month period, 87 nauplii hatched. Of those identified, 98% were B. hamata and 2% Gladioferens pectinatus Brady. This is the first report of B. hamata resting eggs. We conclude that B. hamata in Lake Waihola can use resting eggs to re‐colonise the plankton when conditions are favourable.

Determining the internal structure of the ocean off north‐east New Zealand from surface measurements - Stephen M. Chiswell (New Zealand Journal of Marine and Freshwater Research, 2001)
The assumption that variability in the circulation around the east coast of the North Island of New Zealand can be described using satellite‐derived sea level and temperature and two empirical modes is tested. Potential errors are quantified if such an assumption is used to derive the internal fields from surface observations. Data from 303 CTD (conductivity‐temperature‐depth) casts made in the region between 1994 and 1999 are first tested against a much larger XBT (expendable bathythermograph) data set to show that they are representative of the expected variability, and then used to compute the empirical modes. The empirical modes are not baroclinic modes, but probably represent the lateral meanderings and variations in strength of the East Auckland Current, together with the presence of Rossby waves in this region. If surface temperature and height can be measured precisely, 60–70% of the variance in the internal temperature and velocity perturbations can be explained with the model. The standard deviation of reconstructed internal temperature errors is about 0.6° near the surface and less with depth. The standard deviation in velocity errors is 5 cm s‐1.

Observed and modelled tidal currents in the New Zealand region - Basil R. Stanton; Derek G. Goring; Robert G. Bell (New Zealand Journal of Marine and Freshwater Research, 2001)
Tidal currents derived from current meter measurements are compared with the output from a barotropic tidal model of the New Zealand region. For the semi‐diurnal constituents there was very good agreement for the M 2 tide and good agreement for the S 2 tide. For the diurnal constituents (K l , O l ) it was found that as the amplitude of the constituents decreased so did both the model/observation agreement and the accuracy of the observed tidal ellipse parameters. Consequently it was not possible to decide whether differences arose through shortcomings in the model or in the data. However, the overall performance of the model as a prognostic tool for ocean tidal current simulation appears to be good.

Influence of along‐shore advection and upwelling on coastal temperature at Kaikoura Peninsula, New Zealand - Stephen M. Chiswell; David R. Schiel (New Zealand Journal of Marine and Freshwater Research, 2001)
Thermistor data from around Kaikoura Peninsula, New Zealand, show that in the synoptic band, temperature fluctuations at 1 m are coherent with the along‐shore wind with a 90° phase difference. At 5 m, however, the coherence is not as high, and the phase relationship is in the opposite sense. Along this coast, wind‐driven advection of the coastal current and upwelling have opposite effects on temperature. A simple model is developed which has along‐shore advection and upwelling terms parameterised in terms of the wind and two unknown coefficients. Solving for the coefficients shows that at 1 m, temperature variability is determined by along‐shore advection, whereas at 5 m, temperature variability is determined principally by upwelling.

Evidence of summer parturition in shortfin mako (Isurus oxyrinchus) sharks from New Zealand waters - Clinton Duffy; Malcolm P. Francis (New Zealand Journal of Marine and Freshwater Research, 2001)
A litter of eight near‐term shortfin mako (Isurus oxyrinchus Rafinesque 1810) embryos is described from a 317.5 cm total length (TL) female caught off Hawke Bay, south‐east North Island, New Zealand on 5 February 1999. The embryos (3 males and 5 females) were 67.2–77.0 cm TL. Embryo length, condition, hepato‐somatic indices, and mass of yolk in their stomachs all indicate they were close to birth. This is the first shortfin mako litter reported from New Zealand and is outside the late winter‐early spring parturition period predicted from estimated embryonic and juvenile growth rates. Uterine width data from four mature non‐pregnant females and age‐+ length‐at‐capture data suggest parturition occurs from September to late February (late winter‐mid summer) but is infrequent after January. We suggest that shortfin makos have an extended parturition period, possibly year‐round, with peak parturition occurring in late winter‐spring.

Calorific content of New Zealand marine macrophytes - Miles D. Lamare; Stephen R. Wing (New Zealand Journal of Marine and Freshwater Research, 2001)
Calorific content was measured in 28 species of New Zealand macroalgae. Values ranged from 1.04 to 3.34 kcal g‐1 dry weight (wt), 3.03–5.18 kcal g‐1 ash‐free dry wt, and 0.13–1.75 kcal g‐1 wet wt. Seasonal variation in calorific content was measured in two of these species, Macrocystis pyrifera and Ulva lactuca , both of which showed clear changes in energy content over a 1‐year period. Factors affecting variation in calorific content between species and during the year are discussed, and the application of the current findings to ecological and aquacultural research on New Zealand seaweeds are considered.

Erupted upper teeth in a male sperm whale, Physeter macrocephalus - Nadine J. Gibbs; Edwin J. Kirk (New Zealand Journal of Marine and Freshwater Research, 2001)
An adult male sperm whale (Physeter macrocephalus L.) which stranded in Hawke's Bay, New Zealand, was found to have seven erupted teeth in its upper jaw—six on the left side, and one on the right side. Each upper tooth lay in the side of the pit into which the corresponding lower tooth fitted, and two bore a groove consistent with contact with a lower tooth.

Distribution of macrophytes in New Zealand streams and lakes in relation to disturbance frequency and resource supply—a synthesis and conceptual model - Tenna Riis; Barry J. F. Biggs (New Zealand Journal of Marine and Freshwater Research, 2001)
A conceptual model for the occurrence of common macrophyte species in different freshwater habitats in New Zealand is presented. The model is developed in two steps. First, a classification of freshwater habitats based on the level of disturbance frequency and resource supply in the habitats is performed. Second, a classification of common New Zealand freshwater macrophytes is made based on the appearance of relevant competitive species traits in different combinations of disturbance frequency and resource supply. From this we predict in which habitat each species is most competitive. We discuss how to test and refine the model, especially by gaining more knowledge about the presence and distribution of the plant species in relation to disturbance frequency, based on field and experimental studies. Benefits of a thorough predictive model in relation to the management practices and maintenance of macrophyte vegetation in lakes and lowland streams are discussed.

Mortality of post‐settlement abalone Haliotis iris caused by conspecific adults and wave exposure - J. Reyn Naylor; Paul E. McShane (New Zealand Journal of Marine and Freshwater Research, 2001)
Experimental studies of post‐settlement abalone (Haliotis iris Martyn) indicate that wave exposure and conspecific adults may be important sources of mortality. In aquarium studies, exposure of post‐settlement abalone to grazing by sea urchins (Evechinus chloroticus) and starfish (Patiriella regularis) , animals common in the subtidal habitat of H. iris , resulted in similar survival to control treatments (no grazers). However, in the presence of conspecific adults, the survival of post‐settlement juveniles was approximately half that of control treatments. The major cause of mortality was evidently pedal smothering by adults. Similar results were obtained in field studies in which survival of recently settled abalone was greater in the absence of conspecific adults. Field studies also revealed that the differences between two bays exposed to contrasting wave action were a significant source of variation in post‐settlement mortality. Survival of recruits was greater in the sheltered bay compared with the bay exposed to ocean swells.

Abundance, residency, and habitat utilisation of Hector's dolphins ( Cephalorhynchus hectori ) in Porpoise Bay, New Zealand - Lars Bejder; Steve Dawson (New Zealand Journal of Marine and Freshwater Research, 2001)
Theodolite tracking and boat‐based photo‐identification surveys were carried out in the austral summers of 1995/96 and 1996/97 to assess abundance, residency, and habitat utilisation of Hector's dolphins (Cephalorhynchus hectori van Beneden 1881) in Porpoise Bay, on the south‐east corner of the South Island of New Zealand. Data are consistent with the model of a small resident population that is visited occasionally by members of neighbouring populations. Mark‐recapture analysis of photographically identified individuals, along with data on the proportion of animals bearing identifying marks, indicates a local population of 48 dolphins (95% CI = 44–55) in 1996/97. Dolphins spent a large proportion of their time in a small area inside the bay. Dolphin sightings were more congregated in successive time periods from early morning to late afternoon. No pattern of diurnal movement into and out of the bay was observed.

Assessing the accuracy of drift‐dive estimates of brown trout ( Salmo trutta ) abundance in two New Zealand rivers: A mark‐resighting study - Roger G. Young; John W. Hayes (New Zealand Journal of Marine and Freshwater Research, 2001)
We compared raw drift‐dive counts of adult brown trout (Salmo trutta Linnaeus 1758) with population estimates calculated from mark‐resight techniques on two occasions in two back‐country rivers near Nelson, New Zealand. Trout were caught by angling and marked with colour‐coded dart tags between 1 and 7 days before drift dives were carried out. Drift‐dive counts in the Owen and Ugly Rivers were 57–66% and 21–43%, respectively, of the population estimates calculated using the mark‐resight techniques. Although underwater census is the cheapest and easiest way to census adult trout populations in clear‐water rivers, a large proportion of the trout population may not be seen in rivers with abundant in‐stream cover. Raw drift‐dive counts provide an index of relative abundance that is useful for monitoring changes in trout populations of specific river reaches over time. However, for comparisons between rivers more accurate population estimates are required. We recommend a combined approach of raw drift‐dive counts and the use of mark‐resight techniques to provide the best estimates of trout numbers. As many trout as possible should be tagged to improve the accuracy of mark‐resight studies.

Seasonal movements of short‐beaked common dolphins (Delphinus delphis) in the north‐western Bay of Plenty, New Zealand: Influence of sea surface temperature and El Niño/La Niña - Dirk R. Neumann (New Zealand Journal of Marine and Freshwater Research, 2001)
Movement patterns of small cetaceans are influenced by a great number of variables including prey availability, sea floor profile, thermocline, oxygen minimum layer, and sea surface temperature (SST). Presented here are data on short‐beaked common dolphins (Delphinus delphis L.) in New Zealand, showing a seasonal offshore‐shift in their distribution, which appears to be correlated with SST. D. delphis moved from a mean distance of 9.2 km (SD = 4.42) from shore in spring and summer to a mean distance of 20.2 km (SD = 3.86) from shore in autumn. During warmer La Nina conditions their mean distance from shore was further reduced to only 6.2 km (SD = 2.56), and offshore movement was delayed by a month. Worldwide, D. delphis can be found throughout a wide range of sea temperatures, and it is therefore unlikely that SST is the primary factor influencing their distribution. It is hypothesised, that SST influences the distribution of D. delphis prey, which in turn affects their seasonal movements.

Effects of the presence of subadult longfinned eels (Anguilla dieffenbachii) on cover preferences of juvenile eels ( Anguilla spp.) in replicate channels - G. J. Glova (New Zealand Journal of Marine and Freshwater Research, 2001)
The effects of the presence of subadult (420–875 mm total length (TL)) longfinned eels (Anguilla dieffenbachii Gray) on day‐time cover preferences of three juvenile size groups (small = (A. australis Richardson) and longfinned eels were tested in replicate channels provided with natural (macrophytes, cobbles, woody debris) and artificial (shade, plastic pipes) cover. Macrophytes, cobbles, and woody debris were the most frequently occupied cover by both species of juvenile eel, whereas overhead shade and plastic pipes were rarely used. In most instances, the subadult longfinned eels occupied the macrophytes, the cover type preferred by juvenile eels when tested in the absence of subadult eels. The small juvenile eels used the three natural cover types similarly between species, whereas the cover preferences of medium and large juvenile eels differed between species—whether tested in species unmixed or mixed situations, shortfinned eels preferred macrophytes and longfinned eels preferred cobbles. It is concluded that as juvenile eels increase in size in the wild, their cover preferences will be more restricted because of greater interaction with that of predatory subadult eels in the population.

Influence of reach geomorphology on hyporheic communities in a gravel‐bed stream - D. A. Olsen; C. R. Townsend; C. D. Matthaei (New Zealand Journal of Marine and Freshwater Research, 2001)
The surface sediment, subsurface sediment, and hyporheos were sampled by freeze‐coring at three sites of contrasting geomorphology in a New Zealand gravel‐bed stream. No differences in size class composition were detected among the subsurface sediments of the three sites but the forced pool‐riffle (a stretch of stream where the sequence of pool and riffles is controlled by in‐channel bedrock outcrops) had significantly finer surface sediments than the other sites. The hyporheos of all sites was dominated numerically by insects, including nymphs of Deleatidium and Oniscigaster , and chironomid larvae. Of the non‐insect taxa, Isopoda, Oligochaeta, and Acari were most common. No significant differences existed between total invertebrate density or taxon richness at the sites. Aoteapsyche was found only in the plane bed site, whereas Nesameletus was found only in the forced pool‐riffle. Psilochorema and Nematoda occurred at significantly lower densities in the forced pool‐riffle than in the plane bed or floodplain sites. For most taxa, local variation within a site was greater than that between sites. Total invertebrate density was highest near the sediment surface but no significant differences were found between the three sites in this or any other depth layer. Significant site‐depth interactions were obtained for three taxa ( Zelandobius , Ostracoda, and Oligochaeta) indicating that local geomorphology may result in differential depth distributions of hyporheic species.

Do potential predators induce an avoidance response in Daphnia carinata? - Amber C. Hendry; Carolyn W. Burns (New Zealand Journal of Marine and Freshwater Research, 2001)
Chemicals exuded by predators (kairomones) are known to induce the daytime descent of several species of Northern Hemisphere Daphnia . The vertical migration of New Zealand's native Dapknia carinata King has not been studied, however, and its response to kairomones is not known. We compared the behavioural responses of D. carinata to water from around two predatory fish, common bully ( Gobiomorphus cotidianus ) and inanga ( Galaxias maculatus ), an aquatic insect ( Anisops wakefieldi ), and several concentrations of trimethylamine (TMA), a fish‐mediated chemical. The responses of Daphnia were assessed in nine trials by comparing their vertical distribution in cylinders of water before and after exposure to water that had contained each predator, or TMA. D. carinata did not alter their vertical distribution in response to water from around Anisops . However, they descended when exposed to water from around inanga in 83% of trials and common bully in 67% of trials. They also descended in response to TMA in the range, 112.5–500 μ M. Analysis of these “fish waters” failed to detect TMA at ≥ 20 μ M , so that we cannot conclude that the behavioural cue from these fish is TMA.

Comparison of daily increment formation pattern between sagittae and lapilli of ling ( Genypterus blacodes ) larvae and juveniles collected off Argentina - S. Morioka; L. Machinandiarena (New Zealand Journal of Marine and Freshwater Research, 2001)
Daily growth increments in sagittae and lapilli of ling ( Genypterus blacodes (Schneider, 1801)) larvae and juveniles were investigated. Increment counts of sagittae and lapilli of wild fish were similar up to a length of c. 20 mm total length (TL) (≈50 days old), after which counts on sagittae were higher than for lapilli. Three individuals were kept alive and treated with Alizarin Complexone to determine whether increments formed on a daily basis. The number of increments visible in the lapilli and sagittae after the mark was close to that expected in two of the three fish. In the third fish, the agreement was good for the lapillus but the number of increments on the sagittae was higher than expected. It is believed that subdaily increments cause the overestimation of age in the sagittae. Consequently, the lapillus is considered to be a better structure for daily increment analysis than sagitta in larvae and juveniles of ling.

Bayesian assessment of the SNA1 snapper ( Pagrus auratus ) stock on the north‐east coast of New Zealand - M. N. Maunder; P. J. Starr (New Zealand Journal of Marine and Freshwater Research, 2001)
A statistical catch‐at‐age model was used in a Bayesian context to assess the SNA1 snapper ( Pagrus auratus (Bloch & Schneider, 1801)) stock off the east coast of the North Island of New Zealand. The analysis differs from previous assessments by starting at an exploited population size in 1970 and using a Bayesian framework to describe uncertainty in the estimates of current stock status and projections of future stock status. The model was fit to two tagging biomass estimates and to catch‐at‐age data. Annual recruitment multipliers were estimated by assuming a temperature‐recruitment relationship and fitting to pre‐recruit trawl survey data for the Hauraki Gulf‐Bay of Plenty combined substock (HG‐BoP) and as individual parameters for the East Northland substock (EN). The combined HG‐BoP substock is estimated to be below the biomass level that will support maximum sustainable yield, but will rebuild under current estimated removals. The EN substock is estimated to be above the biomass level that will support maximum sustainable yield and will remain above this level during the next 20 years assuming current estimated removals continue. The initial fishing mortality rate in 1970 is a very important parameter in the model because it is inversely related to the rate of stock rebuilding. Unfortunately the initial fishing mortality rate is not well determined by the data in either assessment.

Abundance, diversity, and structure of freshwater invertebrates and fish communities: An artificial neural network approach - Sebastien Brosse; Sovan Lek; Colin R. Townsend (New Zealand Journal of Marine and Freshwater Research, 2001)
Artificial neural networks (ANN) are models inspired by the structure and processes of biological cognition and learning. To illustrate the ecological applications of ANN, we present analyses of two complementary examples. ANN is first used to predict the diversity of macroinvertebrates, at the macrohabitat scale, in tributaries of a large river in New Zealand and, second, to predict the distribution and abundance of several fish species at the microhabitat scale in a French lake. The predictive abilities of the models were high, with correlation coefficients between observed and estimated values from 0.61 and 0.92. Moreover, the environmental variables found to be associated with invertebrate diversity and fish abundance were in accord with results of previous studies. The combination of ANN with a multivariate analysis offish community composition provided both for accurate prediction of fish assemblages and effective visualisation of their relationships with environmental variables. On the basis of these studies in different locations (New Zealand streams, French lake), involving various population and community attributes, we conclude that ANN is an appropriate tool for both prediction and explanation of ecological relationships at various spatial scales (microhabitat and macrohabitat), and for a range of aquatic ecosystems (lakes and rivers), organisms (invertebrates and fish), and ecological descriptors (abundance, Shannon diversity index, and community composition).

Aspects of the structure and variability of the low‐salinity‐layer in Doubtful Sound, a New Zealand fiord - Mark T. Gibbs (New Zealand Journal of Marine and Freshwater Research, 2001)
The concurrent actions of fresh water input from the Manapouri power station and the extreme precipitation in the catchment of Doubtful Sound, south‐western New Zealand, results in the maintenance of a surface low‐salinity‐layer (LSL). Although the role of the LSL in controlling subtidal and inter‐tidal assemblages in Doubtful Sound has been documented, little is presently known about the characteristics of the LSL itself. The work presented here aims to elucidate particular aspects of the structure and variability of this ecologically important feature. Synoptic hydrographic data collected during the Doubtful Sound Monitoring Program (DSMP) shows that the LSL is robust and maintained throughout all seasons. Furthermore, hourly salinity and temperature data acquired from four sites within Doubtful Sound show that the major source of variability in the LSL lies in the weather bands although the surface temperatures also exhibited a seasonal component. Time‐series analyses of these data revealed that large perturbations in the LSL were associated with the combined actions of the local wind stress and precipitation. In addition, analysis of data from moored quantum PAR (photosynthetically active radiation) sensors revealed the important influence of the LSL on the subsurface light field.

Effects of desiccation on stream epilithic algae - Thorsten D. Mosisch (New Zealand Journal of Marine and Freshwater Research, 2001)
The effect of desiccation on epilithic algae was studied in two subtropical rainforest streams in south‐east Queensland, Australia. Diatom‐dominated algal assemblages on stream‐collected cobbles were subjected to desiccation periods of 15 and 30 days, followed by re‐immersion in the streams for 15 and 30 days. Algal assemblages in the two streams showed different responses to the desiccation and re‐immersion treatments, most likely the result of differences in the physical and chemical characteristics of the two stream ecosystems. Following the re‐immersion treatments, chlorophyll a was significantly reduced in one stream, with no significant changes recorded in ash‐free dry mass. In the second stream, epilithon ash‐free dry mass had increased significantly by the end of the re‐immersion period, while no significant effects of desiccation were measured. Results indicated that, at least in one stream studied, diatom assemblages on the experimental cobbles were not able to withstand short periods of desiccation (15 days) and did not recover after 30 days of re‐immersion in the streams. The results obtained here showed that desiccation must be considered an important factor controlling epilithon communities in streams.

Factors regulating the downstream migration of mature eels ( Anguilla spp.) at Aniwhenua Dam, Bay of Plenty, New Zealand - Jacques A. Boubée; Charles P. Mitchell; Benjamin L. Chisnall; Dave W. West; Eddie J. Bowman; Alex Haro (New Zealand Journal of Marine and Freshwater Research, 2001)
The downstream migrations of mature longfinned eels ( Anguilla dieffenbachii Gray, 1842) and shortfinned eels ( Anguilla australis Richardson, 1848) were investigated at Aniwhenua Dam on the Rangitaiki River between 1992 and 1998. Migrants were mostly females over 1000 mm total length (TL) with otoliths indicating rapid growth rates. Migrations, which occurred on a few nights each autumn, generally began once water temperatures began to decline and ended when temperatures dropped below c. 11 °C. Rainfall and flow increases were found to be key factors triggering migration events. Rainfall exceeding a cumulative total of 40 mm over 3 days accounted for 60% of migrant eels arriving at Aniwhenua. It is proposed that such rainfall triggers could be used as predictors to instigate mitigation activities that would allow mature eels to proceed uninjured past barriers such as hydro‐electric dams.

Effects of turbidity on the migration of juvenile banded kokopu ( Galaxias fasciatus ) in a natural stream - Jody Richardson; David K. Rowe; Joshua P. Smith (New Zealand Journal of Marine and Freshwater Research, 2001)
Laboratory experiments have shown that the juvenile migratory stage of banded kokopu ( Galaxias fasciatus (Gray 1842)) is more sensitive to turbidity than other native fish species and avoids turbidity levels of >25 nephelometric turbidity units (NTU). Field trials using juvenile fish collected from the Tarawera River and Hays Stream, New Zealand, were used to test the results from these laboratory experiments by measuring the effects of turbidity on the migration direction and rate for banded kokopu in a natural stream setting. In the stream setting, neither the migration rate nor the migration direction were affected at turbidity

New species of Spongia (Porifera: Demospongiae: Dictyoceratida) from New Zealand, and a proposed subgeneric structure - Steve de C. Cook; Patricia R. Bergquist (New Zealand Journal of Marine and Freshwater Research, 2001)
This paper is the fifth in a series revising the taxonomy of New Zealand dictyoceratid sponges (phylum Porifera, subclass Ceractinomorpha, order Dictyoceratida). Six new species of the genus Spongia are added to New Zealand's known fauna. The use of subgenera within the genus Spongia is discussed, and two new subgenera are proposed. The genus Hippospongia is revised, and an emended generic diagnosis is proposed.

Diel patterns of mysid drift (Crustacea: Mysidacea) in the Taieri River estuary, New Zealand - Darin L. Sutherland; Gerard P. Closs (New Zealand Journal of Marine and Freshwater Research, 2001)
Drifting mysids were sampled to determine diel activity, and whether mysid numbers vary with respect to inflowing and outflowing tides. Samples of drifting mysids were collected at the mouth of the Taieri River, New Zealand, over one 24‐h cycle using five replicate conical drift nets in January 1999. One‐night and 1‐day ebb and flood tide were each sampled. Four species of mysid Tenagomysis macropsis, T. novae‐zealandiae, T. robusta , and an apparently undescribed species of Gastrosaccus sp., were collected over the sampling period. One species, T. robusta , has not previously been collected from estuarine or riverine systems. The undescribed Gastrosaccus sp. was the most abundant of the four species. All four species were more abundant at night, with T. robusta and Gastrosaccus sp. being considerably more abundant in the drift on outflowing tides. In contrast, roughly equal numbers of T. macropsis and T. novae‐zealandiae were observed drifting in and out of the estuary at night.

Eddy energetics in the subtropical front over the Chatham Rise, New Zealand - Stephen M. Chiswell (New Zealand Journal of Marine and Freshwater Research, 2001)
The Chatham Rise, which rises to a depth of 400 m immediately to the east of New Zealand, appears to constrain the latitudinal movement of the Subtropical Front (STF). Data from current meters moored over the Chatham Rise are used to estimate the spatial variation of mean and turbulent kinetic energies and Reynolds stresses in and around the STF. Mean currents over 8 months are to the east, and are stronger south of the rise. Mean speeds at 250 m south of the rise are as high as 15 cm s −1 compared to 4.5 cm s −1 north of the rise. In contrast, the eddy kinetic energy is higher to the north at 8.2 J m −3 compared to 3.3 J m −3 to the south. Short‐term current meter moorings over the crest of the rise show no coherence over length scales of 15 km for periods less than 10 days. At 250 m depth, Reynolds stresses are positive north of the rise, and negative south of it, suggesting an export of momentum away from the STF.

Burial limits to the emergence of aquatic plant propagules - Tony M. Dugdale; Mary D. de Winton; John S. Clayton (New Zealand Journal of Marine and Freshwater Research, 2001)
The sediment depth limits to germling emergence were determined for five common New Zealand submerged plants. A significant trend was observed of declining emergence with increasing burial depth. Emergence from small oospores (13–16 μg) of Nitella pseudoflabellata A. Br. and Nitella leptostachys A. Br. was limited to the surface sediment ( Potamogeton ochreatus Raoul seed (1460 (μg) emerged from Chara corallina Willd. oospores (148 μg) emerged from burial depths of at least 50–75 mm, while Chara globularis Thuill. oospores (50 (μg) were able to emerge from the maximum tested depth of 100 mm. The observation that burial limits to emergence by Chara species were at least twice that of the much larger P. ochreatus seed is at odds with theory that the size of propagule reserves act to determine emergence ability. However, it is in keeping with suggested energy efficiency of shoot extension in the macroalgae versus vascular species. Results indicate that assessment of submerged seed banks should concentrate on the upper 50 mm of sediment which contains most “ecologically active” propagules.

Distributional expansion of Carpophyllum flexuosum onto wave‐exposed reefs in north‐eastern New Zealand - Russell G. Cole; Russ C. Babcock; Victoria Travers; Robert G. Creese (New Zealand Journal of Marine and Freshwater Research, 2001)
The native fucalean macroalga Carpophyllum flexuosum (Esper) Grev. has recently occupied many reefs on wave‐exposed coasts in north‐eastern New Zealand. At recently colonised sites, C. flexuosum occurs mainly on coralline‐dominated areas with moderate densities of sea urchins ( Evechinus chloroticus ). At these sites, stipes of C. flexuosum are shorter, with more branching, reduced laminae, and increased stipe weights compared to those at sheltered sites. Survivorship of tagged individuals was less on wave‐exposed than on sheltered reefs. On sheltered shores, small C. flexuosum suffered moderate mortality, but large individuals suffered little mortality from any source. All individuals transplanted from sheltered to wave‐exposed shores died or became moribund as stipes, whereas those which survived transplanting from wave‐exposed to sheltered shores assumed a morphology more characteristic of sheltered sites. Population modelling suggested that the existence of stands of C. flexuosum on wave‐exposed shores is dependent on regular recruitment, though it is not clear whether populations are maintained by recruitment from within or without. The establishment of C. flexuosum on wave‐exposed shores is correlated with decadal scale decreases in wave energy. We predict that the patchiness of recruitment of C. flexuosum in space and time (and the ubiquity and reproductive characteristics of the dominant laminarian Ecklonia radiata ) and its susceptibility to wave action will prevent the fucalean from inducing long‐term changes of assemblage organisation.

Parioglossus (Teleostei: Gobioidei: Microdesmidae) in New Zealand - R. M. McDowall (New Zealand Journal of Marine and Freshwater Research, 2001)
The genus Parioglossus is known widely across the Indo‐West Pacific from tropical western Pacific islands (Fiji, Vanuatu, New Caledonia), through eastern subtropical to tropical Australia, in south‐east Asia and north to Japan, and west across the Indian Ocean to Madagascar. It is hitherto not recorded from New Zealand, but is here reported from a stream near North Cape in far northern New Zealand, and another draining a wetland on Great Barrier Island in the north‐east of the country. New Zealand specimens do not conform completely to any published descriptions of Parioglossus , but this seems likely to reflect inadequacies in the published descriptions. The fish appear closest to the eastern Australian P. marginalis . Typical habitat is unclear, though simple testing of euryhalinity suggests an ability to inhabit marine, brackish, and possibly fresh waters. Whether the species has been long present in New Zealand waters, undiscovered, has dispersed to New Zealand across the Tasman Sea in ocean currents, or was brought to New Zealand in ballast water discharged from ships, is not known. Parioglossus is one of several species newly discovered in New Zealand waters, for which various explanations are possible.

New Zealand stream invertebrates: ecology and implications for management. Edited by Kevin J.Collier and Michael J.Winterbourn. Published in 2000 by The New Zealand Limnological Society, Christchurch, New Zealand. 415 p. ISBN 0–473–06679–3. Price: NZ$49.95 (within New Zealand), AUS$45.00 (Australia), US$40 (other countries). Available from: Book Sales, New Zealand Limnological Society, c/‐ NIWA, P.O. Box 11 115, Hamilton, New Zealand.Trout and salmon: ecology, conservation and rehabilitation. By D. TrevorCrisp. Published in 2000 by Fishing News Books, an imprint of Blackwell Science, Osney Mead, Oxford OX2 OEL, United Kingdom. 212 p. ISBN 0–85238–256–1. Price: £39 (email: fnb@blacksci.co.uk). - Andrew J. Boulton; D. Scott (New Zealand Journal of Marine and Freshwater Research, 2001)

Size‐specific clearance, excretion, and respiration rates, and phytoplankton selectivity for the mussel Perna canaliculus at low levels of natural food - M. R. James; M. A. Weatherhead; A. H. Ross (New Zealand Journal of Marine and Freshwater Research, 2001)
Clearance, respiration, and ammonia excretion rates, and phytoplankton selectivity were measured for the Greenshell™ mussel Perna canal‐iculus (Gmelin) in Beatrix Bay, Marlborough Sounds, New Zealand. Functional equations were developed describing the relationship between body size (length and weight) and clearance and metabolic rates for this species feeding on natural food assemblages in New Zealand waters. Relationships with shell length were described by allometric power curves but the relationship with chlorophyll a concentrations in the water for a particular size of mussel suggested there was a threshold between 0.2 and 0.3 μg Chi. a litre −1 and an exponential decline in clearance rate from c. 0.5–0.6 μg Chi. a litre −1 with increasing chlorophyll concentrations. Under these field conditions ingestion rate would increase linearly with increasing chlorophyll concentrations up to c. 0.5 μg Chi. a litre −1 then remain constant at higher chlorophyll levels. Food levels, as measured by chlorophyll a or particulate carbon, were very low (generally a litre −1 and 300 μg C litre −1 ) throughout the study and this was reflected in low ingestion rates, despite clearance rates of up to 8.6 litre mussel 1 h −1 . P. canaliculus generally appears to be non‐selective, at least for phytoplankton in the size range 5–100 μm, but there was some evidence that larger diatoms and dinoflagellates were cleared more efficiently by larger mussels. Some of our observations on food levels and feeding rates help explain the low mussel growth and condition experienced in the Pelorus Sound during 1996–97.

Chemotherapy of the ciliate Trichodina sp. on juvenile turbot {Colistium nudipinnis ) with notes on the susceptibility of fish with abnormal pigmentation - B. K. Diggles (New Zealand Journal of Marine and Freshwater Research, 2000)
Turbot ( Colistium nudipinnis (Waite, 1910)) fingerlings reared from a single batch of eggs during the 1998 breeding season were examined by histopathology during a routine health assessment. Fish exhibiting pigment abnormalities such as brown coloration, extensive ambicoloration, or hypo‐melanisation of the ocular surface were significantly smaller, and had a significantly higher prevalence of kidney lesions and the ciliate Trichodina sp. on the gills than did normally pigmented fish. This suggests that abnormally pigmented fish grew more slowly and were more susceptible to disease. Additional fish were exposed to 12 different chemotherapeutic bath treatments to determine the most effective methods of removing Trichodina sp. Treatments which removed 100% of Trichodina sp. while providing 100% survival offish included 200 ppm formalin for 30 min, 200 ppm formalin for 1 h, fresh water for 30 min, and 25 ppm formalin + 0.08 mg/litre malachite green for 24 h. The recommended treatment against Trichodina sp. for use in a commercial situation is 200 ppm formalin for 30 min. The significance of these findings to culture of turbot in New Zealand are discussed.

Geochemical signatures of discharge waters, Macraes mine flotation tailings, east Otago, New Zealand - D. Craw; M. Nelson (New Zealand Journal of Marine and Freshwater Research, 2000)
The stream catchment containing the tailings dam complex at the Macraes mine, east Otago, New Zealand has three chemically distinct water types. ( 1) Natural groundwater has pH beween 6 and 8, and sulphate levels locally elevated to 30 ppm. The total carbonate/calcium (Ca) ratio is c. 2, consistent with carbonic acid dissolution of basement schist calcite. Sodium (Na) is strongly elevated over chloride, and these levels are dominated by water‐rock interaction. (2) Decant pond waters lie on two tailings dams, one of which was inactive between 1993 and 1998. Their pH is strongly alkaline (8–9). Sulphate, Na, chloride, and Ca contents are higher than groundwater and these levels have risen steadily over time. Carbonate content is lower than groundwater. Arsenic (As) and iron (Fe) contents are high and variable; arsenic in the active tailings pile is commonly 5–15 ppm. (3) Mixtures of tailings water and natural groundwater (c. 1:1) form from seepage from the upper part of the main tailings pile only and mix beneath the main tailings dam to emerge down stream of the dam. The mixture pH (6.3) is slightly lower than that of the groundwater (mainly >7) whereas the sulphate content is high (>1500 ppm) because of the water component of the tailings. There is no resolvable time lag on the 1‐month scale between discharge of tailings water into the dam and emergence at the foot of the dam. Two distinct water types are identifiable in this setting. Chimney drain discharge is collected in pipes and discharged from those pipes. The tailings component of this water is chemically little different from that which left the tailings. Subsurface flow travels unconfined beneath the tailings dam and interacts chemically with the dam aggregate. Attenuation of Na and chloride, and addition of Ca, carbonate, and magnesium (Mg) occurs. Nearly all dissolved As and copper (Cu) was extracted from the subsurface flow during passage through the dam, whereas some As and all Cu is extracted from the chimney drain discharge. A small volume of a mixture of tailings water and groundwater has continued down stream of the tailings dam complex for c. 50 m in the basement schist as a contaminant plume which took c. 2 years to travel that distance in fractures within the schist. This contaminated water is chemically similar to that of the subsurface flow, and has high sulphate content but no detectable As or Cu.

Detecting a response to weak sea breezes in the New South Wales coastal ocean - Mark T. Gibbs (New Zealand Journal of Marine and Freshwater Research, 2000)
Current meter data from the coastal ocean at Sydney, south‐eastern Australia, were analysed to seek evidence of a response to the prevailing summer sea breeze. A response to the sea breeze was found in the currents. This is significant since the magnitude of the sea breeze was small by comparison with winds associated with large‐scale pressure systems and the East Australian Current. Responses were determined by analysing short periods (3–5 days) of sea breeze activity as opposed to the whole 2‐month data set. The correlations between the alongshore nearshore diurnal‐period currents and the local wind stress during the sea breeze periods were significantly higher than the correlations during non‐sea‐breeze periods. Despite the stronger correlations the sea breeze could only account for around one‐quarter of the variance in the diurnal‐period currents. However, the detection of the response to the sea breeze is significant since the sea breeze has never previously been identified as a process for forcing alongshore nearshore currents on this shelf.

Revised estimates of natural mortality for the Foveaux Strait oyster ( Ostrea chilensis ) - Alistair Dunn; H. John Cranfield; Ian J. Doonan; Keith P. Michael (New Zealand Journal of Marine and Freshwater Research, 2000)
We present revised estimates of the instantaneous natural mortality rate of recruited (legal sized) Foveaux Strait dredge oysters ( Ostrea chilensis , Philippi, 1845) for the years 1974–86. A mark‐return experiment was analysed, assuming constant rate of fishing (and hence sampling) over 6 months of the year (i.e., the period of the fishing season). The natural mortality between 1974 and 1986 of recruited oysters increased from 0.02 to 0.19 year 1 for a sample of oysters released in 1974, and from 0.01 to 0.20 year ‐1 for those released in 1973. We explored possible causes for the observed increases including the impact of indirect fishing mortality, rising disease mortality ahead of the Bonamia sp. epidemic of 1986, and systematic mis‐reporting in returns of living and dead tagged oysters. We find no direct evidence for any of these, and hence speculate that the observed increase in natural mortality of the tagged individuals is associated with senescence.

Quantification of the maximal swimming performance of Australasian glass eels, Anguilla australis and Anguilla reinhardtii , using a hydraulic flume swimming chamber - Shane A. Langdon; Adrian L. Collins (New Zealand Journal of Marine and Freshwater Research, 2000)
The swimming performance of Australasian glass eels Anguilla australis Richardson and Anguilla reinhardtii Steindachner was measured within an hydraulic flume over a range of water velocities. Individual swimming performances were characterised as either maximum sustained, steady prolonged, rapid prolonged, or burst. The maximum sustained swimming speeds for A. australis (mean total length (MTL) = 54.2 mm) and A. reinhardtii (MTL = 51.2 mm) were 29 and 32 cm s ‐1 respectively. The maximum burst speeds for A. australis and A. reinhardtii were 79 and 75 cm s ‐1 respectively. Regression analysis revealed two points of inflection corresponding to definite changes in the level of swimming effort occurring at 35 and 64 cm s ‐1 for A. australis , and 42 and 63 cm s ‐1 for A. reinhardtii . Observed differences in the swimming performance of these two species was not significant ( P 0.05). To allow free passage for migrating glass eels in Queensland's regulated rivers, this study recommends that mean and maximum fishway velocities not exceed 30 and 75 cm s ‐1 respectively, and/ or fishway cells be designed to incorporate elements specifically designed to permit glass eel passage.

Population genetic structures of two New Zealand corophiid amphipods and the presence of morphologically cryptic species: Implications for the conservation of diversity - Kareen E. Schnabel; Ian D. Hogg; M. Ann Chapman (New Zealand Journal of Marine and Freshwater Research, 2000)
We evaluated the population genetic structures (allozyme variation) of Chaetocorophium lucas i (Hurley 1954) Karaman 1979 and Paracoro‐phium excavatum (Thomson 1884) Stebbing 1899 (Amphipoda: Crustacea) from the North Island and South Island of New Zealand. Individuals of C. lucasi were found in both freshwater and estuarine habitats, whereas P. excavatum was restricted to estuarine sites. Allele frequencies showed significant inter‐ and intra‐specific differences among populations of both C. lucasi and P. excavatum. C. lucasi appears to be a single species, albeit with considerable genetic differentiation among populations (FSX = 0.51). However, P. excavatum revealed even greater levels of genetic differentiation among populations (F ST = 0.81), and may consist of at least three genetically distinct species. Geographic distance, perhaps dictated by prevailing ocean currents and overland dispersal routes, best explained observed patterns of differentiation among populations of both species. From a conservation perspective, the presence of morphologically cryptic species suggests that current taxonomic inventories of aquatic amphipods may be grossly underestimated.

New Zealand's National River Quality Network - R. G. Death; I. M. Henderson; M. K. Joy; M. R. Scarsbrook; J. M. Quinn; I. K. G. Boothroyd (New Zealand Journal of Marine and Freshwater Research, 2000)

Timing and habitat of koaro ( Galaxias brevipinnis ) spawning in streams draining MtTaranaki, New Zealand - Richard M. Allibone; Dean Caskey (New Zealand Journal of Marine and Freshwater Research, 2000)
A spawning site of Galaxias brevipinnis Giinther was located in a New Zealand stream for the first time. It was at the edge of a riffle and only partially submerged. The habitat used for spawning matched that described for G. brevipinnis in Australia. Spawning was estimated to have occurred between late April and early May and the eggs hatched in late May. The species of fish spawning was identified by rearing the eggs through to identifiable juveniles and by DNA sequencing of one individual.

Reproduction in the intertidal limpet Cellana ornata in southern New Zealand - R. A. Dunmore; D. R. Schiel (New Zealand Journal of Marine and Freshwater Research, 2000)
The reproductive cycle of the abundant intertidal limpet Cellana ornata (Dillwyn 1817) was examined over 19 months, covering two breeding periods, on a rocky intertidal platform in southern New Zealand. A gonad index was calculated, and histological sections were used to count the numbers of mature and immature eggs present. Fecundity was estimated using counts of eggs before and after spawning. To determine any variation between sites, the gonad index of limpets at a second site dominated by boulders was examined over 6 months during the second breeding period. C. ornata had a single spawning period annually during summer, with greatest gonad sizes in January‐February. There were significant differences in peak gonad indices between two breeding seasons on the platform. Within the second breeding period, both the timing and magnitude of peak gonad development differed between sites, with lower reproductive output at the boulder site. Fecundity increased with increasing size, but individuals are probably capable of reproducing after their first year on the shore. The life history of this species is discussed in comparison to other limpets in New Zealand.

Sediment facies and pathways of sand transport about a large deep water headland, Cape Rodney, New Zealand - Terry M. Hume; John W. Oldman; Kerry P. Black (New Zealand Journal of Marine and Freshwater Research, 2000)
Cape Rodney is a large headland that protrudes 3–4 km into deep water in the Hauraki Gulf and separates the Mangawhai‐Pakiri and Omaha littoral cells. Detailed swath mapping of seabed sediments around Cape Rodney was carried out using by side‐scan sonar and ground‐truthed by SCUBA, grab sampling, and video. Despite the barrier imposed by the headland two pathways of sand transport around the headland, separated by the topographic high of Leigh Reef, have been identified. One lies close to the headland, where sand from the beach and nearshore of the Mangawhai‐Pakiri embayment is driven by waves and currents along a 500‐m‐wide pathway in c. 20–25 m depth around the headland to the vicinity of Leigh Harbour. The other lies in 50 m water‐depth seawards of Leigh Reef. Here fine sand, sourced from the nearshore of the Mangawhai‐Pakiri embayment and driven offshore from the tip of the headland, is transported back and forth by tidal currents in 50 m water depth on the floor of the Jellicoe Channel. The sand bodies along both these pathways are thin and so sand leakage from the Mangawhai‐Pakiri embayment is thought to be small. Transport at these depths is dependent on both tide and wave generated currents and episodic occurring during storm events. The sediment facies associated with little sand transport about a headland in deep water is one of thin and discontinuous and patchy sand cover between rocky areas and over coarser megarippled substrate. Ocean swell, tidally driven phase eddies that spin up on both sides of the headland, and bathymetry all play a role in shaping those facies.

Wind wave characteristics at Lake Dunstan, South Island, New Zealand - Jonathan C. Allan; Robert M. Kirk (New Zealand Journal of Marine and Freshwater Research, 2000)
Information on wave statistics, seasonal characteristics, and their distribution about lacustrine shorelines is virtually non‐existent. The absence of such data limits the effective management of lake shores where issues of shoreline erosion are no less significant than on open ocean coasts. Results from instrumentally measured waves during seven storm events in 1995 are presented for the Clutha Arm of Lake Dunstan, South Island, New Zealand. The significant wave height ranged from 0.07 to 0.57 m with a mean of 0.28 m, whereas the maximum wave reached 1.05 m. Peak spectral wave periods ranged from 1.7 to 3.6 s with a mean of 2.46 s. The largest and most destructive waves are observed along the southern shore of the Clutha arm where fetch lengths are at their maximum. These waves exhibit the longest and widest range of periods and are generally the steepest waves, making them highly erosional at the shore. Correlations of waves with those predicted by NARFET, a deepwater wave‐hindcasting computer model, revealed reasonable predictions of the wave height ( R = 0.77–0.81), particularly for sites exposed to longer fetches, while the correlations with the wave period were lower ( R = 0.56–0.69). Wave hindcasting indicates that the wave regime in the Clutha Arm is bi‐directional, with most waves arriving from the north or south. Findings from Lake Dunstan have important implications for larger lakes located throughout New Zealand, where considerably larger waves can be expected to occur during severe storm events.

Neophrynichthys heterospilos , a new species of fathead sculpin (Scorpaeniformes: Psych rol utidae) from New Zealand - Keith L. Jackson; Joseph S. Nelson (New Zealand Journal of Marine and Freshwater Research, 2000)
A second species of Neophrynichthys is described from 20 specimens collected from the Campbell Plateau, south of South Island, New Zealand. It differs from its sole congener, N. latus , in having 25–26 pectoral rays (versus 22–24), cirri on head more than twice as large, half as few (c. 50 versus >100), and generally absent from the mid‐region behind the eyes (versus being relatively dense), and in spotted colour pattern covering much less than 50% of the dorsal surface of the head (versus >50%). This new species is the sixth psychrolutid known from New Zealand. The genus Neophrynichthys is formally diagnosed by two synapomorphic characters unique among psychrolutids: having light spots on a dark ground colour and having an open fourth and fifth infraorbital, fifth and sixth cranial arch, medial extrascapular, and posterior tabular of the pterotic.

Larval development of Boccardia knoxi , a shell‐infesting spionid polychaete - Sean J. Handley (New Zealand Journal of Marine and Freshwater Research, 2000)
Larvae of Boccardia knoxi (Rainer) were reared in the laboratory after dissection from brood capsules extracted from the outer shell and perio‐stracum of Cookia sulcata and Haliotis iris collected from Tasman Bay, New Zealand. All the eggs within each brood capsule developed into embryos. The dissected larvae had provisional setae and fed on phytoplankton. Larval development is described through to metamorphosis.

New Zealand wave climate from satellite observations - Andrew K. Laing (New Zealand Journal of Marine and Freshwater Research, 2000)
Wave data derived from radar altimeters carried on four satellite missions are combined into a wave climatology for New Zealand waters. These data provide extensive observations of wave conditions around New Zealand, where the paucity of measurements has previously hindered definition of the wave climate. The data span the period 1985 to the present with the exception of a 2‐year gap in 1989–91. The spatial distribution of the long‐term mean of significant wave heights (SWH) indicates a strong latitudinal variation in the south‐west Pacific, with values of over 4 m at latitudes of 50–60°S and under 2.5 m towards the tropics. The shadowing of New Zealand is quite marked; a result of the dominant contribution of south‐westerly wave events. The annual range of the mean SWH also varies over the region; within 0.6 m in the north and 1.3 m in the south. A principal component analysis of the monthly anomalies in mean SWH identifies spatial patterns of variation. Some components vary with the local wind more than others suggesting that some anomalies are associated with wind sea and some with swell. Some patterns also appear to vary with the Southern Oscillation Index and can be related to the wind anomalies associated with El Nino events. Frequency distributions of SWH are also determined, and it is noted that in the north of the region the spatial pattern of the high waves differs considerably from the means.

Influence of the small intertidal seagrass Zostera novazelandica on linear water flow and sediment texture - Wiebke M. Heiss; Abigail M. Smith; P. Keith Probert (New Zealand Journal of Marine and Freshwater Research, 2000)
The influence of a small intertidal seagrass, Zostera novaz.elandica (Setchell), on tidal current velocities and sediment texture was studied at Harwood, Otago Harbour, New Zealand. Tidal current velocities were substantially reduced inside the Z. novazelandica patch compared to velocities above the patch (3.7 times greater) and outside it (2.5 times greater), causing a low‐flow environment among the 12‐cm‐tall seagrass. Current velocities combined over one tidal cycle occupied a much wider range outside ( 1.2‐A.b cms ‐1 ) and above ( 1.9–7.1 cm s ‐1 ) the seagrass patch than inside (0.1–1.8 cm s ‐1 ) indicating slower and less variable water flow. Suspended mud ( novazelandica may reduce water flow and accumulate finer sediment sizes to a lesser extent than larger subtidal seagrass species.

Distribution and movements of brown ( Salmo trutta ) and rainbow trout ( Oncorhynchus mykiss ) in Lake Otamangakau, central North Island, New Zealand - M. Dedual; I. D. Maxwell; J. W. Hayes; R. R. Strickland (New Zealand Journal of Marine and Freshwater Research, 2000)
The post‐spawning movements and distribution of 15 brown trout ( Salmo trutta Linnaeus 1758) and 21 rainbow trout ( Oncorhynchus mykiss Richardson, 1836) were monitored weekly between August 1996 and March 1997 in the hydro‐electric reservoir, Lake Otamangakau, New Zealand, using radio‐telemetry. The most frequently used areas were the vicinity of the main inflow and the channel running through the main body of the lake. After spawning, brown trout regained rapidly their usual habitat. Rainbow trout were using the inlet intensively before recolonising the main channel of the lake. Brown trout made greater use of the weedy parts of the lake and littoral margins, had a more confined home range, and were less mobile than rainbow trout. Rainbow trout occupied the main body of the lake by day, and moved nearer the surface, and closer to the margins, at night. High lake levels allowed brown trout to exploit wetland margins of the lake.

Neolepas osheai sp . nov., a new deep‐sea vent barnacle (Cirripedia: Pedunculata) from the Brothers Caldera, south‐west Pacific Ocean - John S. Buckeridge (New Zealand Journal of Marine and Freshwater Research, 2000)
Neolepas osheai sp. nov. is described from collections made at depths of 1200–1700 m within the Brothers Caldera, a site of hydrothermal venting and active volcanism in the southern portion of the Havre Trough. N. osheai sp. nov. is similar to other Neolepas in that it is hermaphroditic, has very specialised cirri, and occupies a “deep water” hydro‐thermal vent habitat. It differs from other species in its trophic structures and the nature of the peduncle. This new record increases the number of described Neolepas species to four, three of which are living. The other, a fossil, is however tentatively ascribed to the genus and is known in rocks of Early Jurassic age. All are from the Southern Hemisphere.

Seasonal, interannual, and decadal variability of storm surges at Tauranga, New Zealand - W. P. de Lange; J. G. Gibb (New Zealand Journal of Marine and Freshwater Research, 2000)
A database of storm surge events was constructed for two sites in south‐eastern Tauranga Harbour, New Zealand, for the period 1960‐mid 1998. Storm surge events were defined as occasions when the residual level between the predicted high tide level and recorded water level exceeded 10 cm. The residual was determined at high tide only (every 12.4 h), with 954 storm surge events found over the 38.4‐year period analysed. The magnitude and frequency of storm surge events varied considerably between 1960 and 1997, withamarked shift evident c. 1976. The period from 1976 to 1997 corresponded to a reduced storm surge frequency and magnitude, compared to the period 1960–76. Wavelet analysis of 125 years of wind storm annual frequencies showed strong fluctuations at inter‐decadal periods. Therefore, it is suggested that the frequency of storm surges varies in response to a coherent inter‐decadal oscillation in surface temperature over the Pacific Ocean, known as the Inter‐decadal Pacific Oscillation (IPO), that reversed phase c. 1976. The El Nino Southern Oscillation (ENSO) also affected the number of days exceeding the storm surge threshold per year, with La Nina events being associated with more storm surge days. The presence of significant decadal variations indicates that annual exceedence probability distributions may misrepresent the storm surge hazard. The available data indicates that there are extended periods when the IPO increases the hazard, and others when the hazard is decreased. Existing analyses of storm surge hazard for the Bay of Plenty have largely been based on data obtained during a period of reduced hazard. Conditions that were associated with larger and more frequent storm surges during 1960–76 may be expected to prevail again over the next few decades.

Intraspecific burrow plasticity of an intertidal population of Callianassa filholi (Crustacea: Decapoda: Thalassinidea) in relation to environmental conditions - Katrin Berkenbusch; Ashley A. Rowden (New Zealand Journal of Marine and Freshwater Research, 2000)
Burrow morphology and intraspecific burrow plasticity in relation to environmental conditions were examined for an intertidal population of Callianassa filholi Milne‐Edwards, 1878 in southeastern New Zealand. Multivariate analysis of burrow features revealed no significant differences in burrow morphology between seasons. However, dissimilarities between burrows from different seasons could be identified and included differences in lateral extent, total length, and volume of burrows. These size parameters each showed low values in winter, coinciding with low seawater temperature and high organic content of the sediment. There was no significant relationship between any of the three size parameters and sediment grain size or shore height of the burrow, but lateral extent and total length of the burrow were significantly related to organic content of the sediment, decreasing with increasing organic content. Furthermore, there was a significant positive relationship between seawater temperature and total length of the burrow. Data from the present study imply that intraspecific variation in burrow morphology for callianassids is dependent on environmental variables, which has consequences for the construction of useful burrow models.

Diadromy and longitudinal patterns of upstream penetration of freshwater fish in Taranaki, New Zealand - Michael K. Joy; Ian M. Henderson; Russell G. Death (New Zealand Journal of Marine and Freshwater Research, 2000)
Diadromous fish species dominate the New Zealand freshwater fish fauna and make up 15 of the 17 native fish species found on the Taranaki Ring Plain. Trajectories of occurrence in relation to elevation and distance from the sea are described for 11 diadromous and 2 non‐diadromous species using data from the New Zealand Freshwater Fish Database and data collected over the summer of 1997/ 98. Distinctive distributions were found for most of the species related to their differing migratory strategies and abilities. The species were ranked based on components of these trajectories to compare their penetrative ability. Comparison of the ranking methods used revealed they produced similar results. The ranking of the 11 diadromous species in Taranaki relative to each other revealed similar rankings to those for the same species from the West Coast of the South Island. The non‐migratory native fish, Cran's bully ( Gobiomorphus basalis ), was not found on the western side of the mountain. This distribution is thought to be the result of the local extinction of non‐migratory species in high gradient or unstable streams.

Age, growth, and movements of giant bullies (Gobiomorphus gobioides) in the Kakanui River estuary, South Island, New Zealand - D. J. Jellyman; P. M. Sagar; G. J. Glova; J. R. E. Sykes (New Zealand Journal of Marine and Freshwater Research, 2000)
The giant bully, Gobiomorphus gobioides (Valenciennes), is widespread throughout New Zealand, but remains one of our least known freshwater fish. During a study of seasonal fish abundance and movements in the Kakanui River estuary, South Island, New Zealand, giant bullies captured mainly in fyke nets were measured and tagged. Growth rates and movements were calculated for the 19 fish recaptured. Growth rates corresponded with mean growth rates back‐calculated from otoliths— scales were considered to overestimate age, and no age classes were evident from length‐frequency distributions. Seasonal changes in condition were associated with spawning during spring‐summer.

Habitat stability and interspecific associations among invertebrate assemblages in New Zealand streams - Russell G. Death (New Zealand Journal of Marine and Freshwater Research, 2000)
To explore whether biotic interactions may be more common in benthic invertebrate communities in stable compared with unstable New Zealand streams, interspecific associations of invertebrate stone assemblages were examined in 10 streams of similar geomorphological character but differing stability. More significant correlations were found than expected by chance at most sites. Stable sites had more negative and positive associations than the unstable sites, although in most instances there were similar numbers of positive and negative correlations. The variance ratio test indicated an overall positive association when all taxa were considered. However, negative associations occurred between a significant number of taxa and were more common at stable sites. Although it remains to be seen whether the negative associations are a result of competition, it does seem biotic interactions are more common in the stable streams than in the flood prone ones as predicted by the harsh‐benign hypothesis.

Pseudo‐nitzschia multistriata (Bacillariophyceae) in New Zealand - Lesley L. Rhodes; Janet Adamson; Chris Scholin (New Zealand Journal of Marine and Freshwater Research, 2000)
Pseudo‐nitzschia multistriata (Takano) Takano has been observed in seawater samples from the North Island and from the northern waters of the South Island, New Zealand, with blooms of >1.0 × 10 6 cells litre ‐1 being recorded in December 1997 (austral summer), and minor blooms occurring in both summer and winter 1998 and 1999. The species is notable for its sigmoid form, and for its cross‐reactivity with oligonucleotide probes targeted at P. australis Frenguelli ribosomal RNA. The species is non‐toxic, and for biotoxin monitoring purposes needs to be discriminated from the highly toxic P. australis . It falls in the “delicatissima” complex of Pseudo‐nitzschia H. Peragallo species, and electron microscopy shows a close resemblance to P. delicatissima (Cleve) Heidin, except for the lack of a central larger interspace.

Habitat use and longitudinal distribution patterns of native fish from a near pristine Stewart Island, New Zealand, stream - W. Lindsay Chadderton; Richard M. Allibone (New Zealand Journal of Marine and Freshwater Research, 2000)
Distribution, abundance, and habitat preferences of native fish were investigated down the length of a relatively pristine, medium‐sized, fourth‐order stream on Stewart Island, New Zealand. A limited fish fauna was recorded (six species), including three threatened large galaxiid species (Galaxias argenteus, Galaxias fasciatus , and Galaxias brevipinnis) , which have restricted distributions on mainland New Zealand. Results indicated that these large galaxiids occupy diverse habitats including pools and backwaters within the mainstems of this stream. Their extensive distributions and wide habitat usage were attributed to factors such as the intact catchment vegetation, unmodified stream channel, and the absence of introduced fishes, particularly salmonids. Results suggest that some native species have been excluded from mainstem habitats elsewhere in New Zealand. It was also evident that interactions among the native species influenced habitat use; G. brevipinnis avoided backwaters, runs, and pools in reaches occupied by G. fasciatus and Anguilla dieffenbachii; whereas G. fasciatus appeared to avoid habitats occupied by G. argenteus and A dieffenbachii . Maximum densities and biomass of galaxiids and eels occurred in deepwater habitats (>0.75 m). Furthermore the fish inhabiting these deeper waters were larger and more likely to be female. These findings have significant implications for the design and application of sampling protocols for native New Zealand fishes and for the protection of their habitats. If deeper waters are not sampled then species, sex, and size biased data may result.

Polychaetes & allies: the southern synthesis. Fauna of Australia Volume 4A. Polychaeta, Myzostomida, Pogonophora, Echiura, Sipuncula. Edited by Pamela L.Beesley, Graham J. B.Ross, and Christopher J.Glasby. Published in 2000 by CSIRO Publishing, P. O. Box 1139, Collingwood, Vic 3066, Australia (http://www.publish.csiro.au/). 477 p., hardback. ISBN: 0–643–06571–7. Price: A$185.00 (email: sales@publish.csiro.au). - Geoffrey B. Read (New Zealand Journal of Marine and Freshwater Research, 2000)

Summer spatial patterns of the fish community in a large, shallow, turbid coastal lake - G. J. Glova; P. M. Sagar (New Zealand Journal of Marine and Freshwater Research, 2000)
Several water quality parameters, marginal vegetation, and the fish community in Lake Ellesmere, a large, shallow, turbid lake situated on the east coast of the South Island, New Zealand, were sampled along selected transects in late summer to determine species spatial patterns. Thirteen species offish were caught, with seven of them comprising major populations, although only four of these were adequately sampled by the method used—they included inanga ( Galaxias maculatus ), common smelt {Retropinna retropinna ), shortfinned eel ( Anguilla australis ), and common bully ( Gobiomorphus cotidianus ). Inanga were almost exclusively confined to areas on the western side of the lake which has a convoluted shoreline with a variety of small embayments with scattered vegetation along the margins. Common smelt occupied both marginal and offshore areas, but they too were more abundant along the margins particularly on the western side. Both the common bully and shortfinned eel were widespread and abundant in the lake, although their abundance and biomass were higher within the vicinity of the lake outlet, major inflowing tributaries, and other marginal habitats. All three species of flounders of the genus Rhombosolea were poorly represented in our samples. However, in commercial catches they were reasonably abundant, with the sand flounder ( R. plebeia ) and yellowbelly ( R. leporina ) being more common in offshore than inshore catches, whereas the black flounder ( R. retiaria ) showed no difference in the catches between areas. Our overall findings are consistent with the hypothesis that bottom‐dwelling species (eels, bullies, flounders) are more widely distributed than free‐swimming forms (inanga, common smelt), which were largely confined to areas sheltered from prevailing winds. The highly turbid nature of the lake, primarily because of re‐suspension of fine bottom sediments by frequent winds, is considered an important factor in the distribution of the fish fauna.

Diet of southern Buller's albatross ( Diomedea bulleri bulleri ) and the importance of fishery discards during chick rearing - Gavin D. James; Jean‐Claude Stahl (New Zealand Journal of Marine and Freshwater Research, 2000)
Southern Buller's albatrosses ( Diomedea bulleri bulleri Rothschild) are frequently associated with fishing vessels off southern New Zealand, and may depend substantially on discards from fishing vessels, particularly trawlers, during chick rearing. To test this hypothesis, the diet was determined from 188 chick regurgitations collected at The Snares (May 1996, July 1996 and 1997) and Solander Island (May and July 1997). Fish (mostly discards but also some small species obtained naturally) was the dominant prey category, occurring in 92% of samples, and forming 65% by weight of solid food consumed. Salps (Pyrosoma sp. and lasis zonaria ) were the most abundant prey items (44% of all items), and second most important by frequency of occurrence (78%) and weight (24%). Cephalopod remains (mostly arrow squid ( Nototodarus spp.) and Histioteuthis atlantica ) occurred in 53% of samples, but contributed only 17% by number and 7% by weight. Other dietary items included crustaceans (chiefly Munida gregaria, Nectocarcinus antarctica , and Lepas anatifera ), bird feathers, and flotsam. Fishery discards were present in 70% of samples, constituted 60% of the diet by weight, and comprised 91% of the weight of all fish consumed. Discard composition was dominated by Gadiformes (mostly hoki ( Macruronus novaezelandiae ) and macrourids) in 1996, and by jack mackerel ( Trachurus sp.) in 1997. Breeders at The Snares took more discards in July 1997 (68 g per sample) than May or July 1996 (31 and 28 g respectively), those at Solander Island took more in May (56 g) than July 1997 (29 g). In May 1996, the diet of birds at The Snares tended to be biased towards fish (both discards and natural prey) after long foraging trips, but towards cephalopods after short trips. Sexual differences in diet and discard consumption tended to be more pronounced amongst samples from The Snares. The high, and apparently increased proportion of fish in the diet, strongly suggest that discards from fishing operations have a beneficial effect on the population of southern Buller's albatrosses breeding on The Snares.

Preliminary observations on breeding and rearing the seahorse Hippocampus abdominalis (Teleostei: Syngnathidae) in captivity - C. M. C. Woods (New Zealand Journal of Marine and Freshwater Research, 2000)
A small‐scale preliminary investigation into the breeding and rearing of the seahorse Hippocampus abdominalis Leeson, 1827 in New Zealand was conducted using 12 wildbroodstock. These broodstock were maintained in a hatchery for breeding and the breeding behaviours exhibited by these were observed and described. Over a period of 6 months a total of 12 broods of juveniles were produced. These were then raised on a diet consisting mainly of enriched Artemia for a period of 1 year. After this period juveniles had reached a mean ± 1 SE total length of 110.73 ±0.13 mm, mean ± 1 SE wet weight of 3.07 + 0.23 g, and were reproductively mature. The mean + 1 SE survival per brood after 1 year was 10.57 ± 3.49%.

Effect of brine shrimp size on the consumption rate, growth, and survival of early stage phyllosoma larvae of the rock lobster Jasus edwardsii - Lennard J. Tong; Graeme A. Moss; Megan P. Paewai (New Zealand Journal of Marine and Freshwater Research, 2000)
Stages I, III, and V phyllosoma larvae of the rock lobster Jasus edwardsii (Hutton) were fed daily with 40, 80, 160, or 320, 1‐mm brine shrimps ( Artemia salina ) while controls were fed either 4, 8, or 16, 2–3‐mm brine shrimps. Stage I larvae fed 1‐mm brine shrimps moulted in the same time as the controls. Stage III and V larvae fed 160,1 ‐mm brine shrimps or less took significantly longer to moult than the controls but those fed 320, 1‐mm brine shrimps were not significantly different. There was no difference in the survival rates, which ranged between 70 and 100% for all stages. The consumption rate increased significantly as the initial density of 1‐mm brine shrimps increased.

Distribution of the New Zealand crayfish Paranephrops zealandicus in relation to stream physico‐chemistry, predatory fish, and invertebrate prey - Nisikawa Usio; Colin R. Townsend (New Zealand Journal of Marine and Freshwater Research, 2000)
Summer distributions of the crayfish Paranephrops zealandicus White, and of potential predators and prey, were investigated in 30 pools along a stream in Otago, New Zealand. Environmental variables were regarded as independent and invertebrates as dependent variables for young‐of‐the‐year (YOY) and adult crayfish. YOY and adults were negatively associated with trout presence and suspended solid concentrations, and positively with wood cover. Adults were further negatively associated with current velocity and positively with depth, leaf cover, and percentage sand. In contrast, YOY were positively associated with coarse substrates. The results are consistent with hypotheses that crayfish are vulnerable to sedimentation and trout predation. Furthermore, coarse substrate and cover may be important because they provide shelter from predation and cannibalism. Deep habitat, however, may act as a refuge from terrestrial predators and/or provide detritus storage for adult crayfish. Densities of adults were negatively associated with those of Megaleptoperla , Tanypodinae, and Scirtidae, but positively with Chironominae. The negative relationships are probably consequences of bioturbation and predation by crayfish. However, the positive relationship with Chironominae indicates that any pre‐dation/bioturbation effect may be outweighed by crayfish shredding leaves and enhancing food supply for these collector invertebrates. The effects of crayfish may propagate into lower trophic levels both directly and indirectly.

Preliminary performance assessment of an underwater line setting device for pelagic longline fishing - Declan O'Toole; Janice Molloy (New Zealand Journal of Marine and Freshwater Research, 2000)
Baited branchlines were set from a tuna longlining vessel using an underwater setting device and their sink patterns compared with those of baited branchlines that were hand‐thrown. Using a paired /‐test at an hypothesised mean difference of 2 m, at a point 100 m astern of the vessel, baited branchlines set using the device were significantly deeper than those that were hand‐thrown. Baited branchlines set using both methods showed a high variation in then‐sink patterns; on some sets they sank faster than others. The underwater setting device has potential to reduce seabird bycatch substantially with minimal intrusion on the normal operation of a longline fishing vessel. It delivers baits underwater (removing the visual cue of a hand‐thrown baited hook to seabirds) and immediately places baited hooks outside the diving range of some vulnerable albatross species ( Diomedea spp., Phoebastria spp., Thalassarche spp., and Phoebetria spp.).

Reduced abundance of banded kokopu ( Galaxias fasciatus ) and other native fish in turbid rivers of the North Island of New Zealand - David Rowe; Murray Hicks; Jody Richardson (New Zealand Journal of Marine and Freshwater Research, 2000)
Laboratory experiments demonstrated that migrant juvenile banded kokopu ( Galaxias fasciatus Gray) were more sensitive to suspended sediment (SS) than other native fish species. If juvenile migrants avoid waters made turbid by SS and their recruitment to adult habitats up stream is reduced, then adult abundance may decline in turbid rivers. To test this, we compared the abundance of diadromous native fish between turbid and clear rivers. The duration (% time) for which SS concentrations exceeded 120 mg litre ‐1 (a critical level from laboratory experiments) during the migration season (August‐December) was estimated for over 150 New Zealand river sites. Turbid rivers were defined as those where SS concentrations exceeded 120 mg litre ‐1 for over 20% of the time and clear rivers as those where SS concentrations exceeded 120 mg litre ‐1 for less than 10% of the time. Eight turbid rivers and seven clear ones were identified where sufficient data on SS and native fish populations existed to permit a comparison. The mean occurrence of banded kokopu was reduced by 89.5% in turbid rivers and, although other diadromous fish species were also less common, banded kokopu was most affected. Densities of adult banded kokopu were also significantly lower in optimal stream habitats in three turbid compared with three matched clear rivers. We therefore concluded that the abundance of adult banded kokopu was reduced in turbid rivers and propose that this is because of reduced recruitment of juveniles in turbid rivers.

Erratum (New Zealand Journal of Marine and Freshwater Research, 2000)

Variability in low tide populations of tuatua, Paphies donacina , in Pegasus Bay, Canterbury, New Zealand - I. D. Marsden (New Zealand Journal of Marine and Freshwater Research, 2000)
Paphies donacina (Spengler, 1793) populations were surveyed at 11 low tide sites on surf beaches along Pegasus Bay, Canterbury, New Zealand, during summer 1998. Random sampling was not feasible. At the non‐random sites chosen the average number of tuatua per 5 m of shoreline ranged between 0.1 and 62. Total wet weight biomass m ‐2 was highest at the southern sites in the Bay. There were site‐related differences in length frequency distributions of tuatua populations. Northern populations included a wide length range and southern populations were dominated by larger bivalves. Average shell length increased significantly with distance south, being close to 40 mm at Waikuku and 80 mm at Taylors Mistake. The shell length: width and weight relationships were similar for tuatua collected over the whole geographic range. Average dry weight condition index varied significantly between sites (ANOVA F= 23.3, d.f. = 10, 329) depending on the length distribution of the contributing population. Where populations included a wide length range the condition index was positively correlated with shell length but in populations dominated by larger bivalves there was either no relationship or a negative relationship with shell length. Juvenile tuatua were found at average densities between 81 and 1200 m ‐2 at all sites except Taylors Mistake. The mean length of recruits ranged from 2.2 to 3.1 mm and shell length was independent of both juvenile and adult density. These results are discussed in relation to the environmental and other factors thought to influence population structure and recruitment of tuatua in Pegasus Bay.

Redescription of the rare slickhead Mirognathus normani (Salmoniformes: Alepocephalidae) with the first record from the western South Pacific - Yuri I. Sazonov; Peter R. Last (New Zealand Journal of Marine and Freshwater Research, 2000)
The rare and inadequately‐defined abyssal slickhead, Mirognathus normani Parr (F. Alepocephalidae), is redescribed based on Atlantic material and the first specimen collected from the Pacific Ocean.

Assemblage structure, spatial patterns, recruitment, and post‐settlement mortality of subtidal bivalve molluscs in a large harbour in north‐eastern New Zealand - R. G. Cole; P. J. Hull; T. R. Healy (New Zealand Journal of Marine and Freshwater Research, 2000)
Infaunal bivalve molluscs on the flood tidal delta of Tauranga Harbour, north‐eastern New Zealand, were surveyed twice over a 6‐month period, with the aim of assessing shellfish resources, assessing the magnitudes of temporal and spatial variability in abundances, and identifying potentially important processes. The surveys identified a total of 31 bivalve taxa from 27 sites. Species richness per site ranged between 0 and 9, and varied greatly in space and time, as did two other measures of diversity. Extremely high densities of bivalves (>20 000 m ‐2 ) were encountered at several sites. Densities of several abundant species varied greatly in time, as a result of recruitment pulses. The abundances of the three species that dominated the fauna ( Paphies australis, Tawera spissa , and Ruditapes largillierti ) had characteristic spatial scales on the order of 200 m. Comparisons of size frequency distributions for individual sites suggested that mortality or emigration in the first year of benthic life was high. Substantial populations of bivalves occur on Centre Bank, and the most abundant of these are greatly influenced by events early in their lives.

Stable isotope composition of modern bryozoan skeletal carbonate from the Otago Shelf, New Zealand - Stephen F. Crowley; Paul D. Taylor (New Zealand Journal of Marine and Freshwater Research, 2000)
The oxygen (δ 18 O) and carbon (δ 13 C) isotope ratios of 10 species of living Bryozoa collected from the Otago Shelf, New Zealand were analysed to assess the extent to which isotopic equilibrium (relative to inorganic equilibrium isotope fractionation) is attained during the precipitation of skeletal calcium carbonate. The data reveal that whereas eight species of Bryozoa synthesise skeletal carbonate in apparent oxygen isotope equilibrium with respect to environmental conditions, two species ( Celleporina grandis and Hippomonavella flexuosa ) yield δ 18 O calcite values which indicate significant disequilibrium oxygen isotope fractionation during calcification. Sufficient data are available from one species ( C. grandis ) to demonstrate that disequilibrium is probably related to kinetic factors associated with diffusion‐controlled transport of HCO 3 ‐ to the site of calcite precipitation. Carbon isotope signatures indicate significant departures from inorganic isotope equilibrium in all but one bryozoan species ( Hippomenella vellicata ). Although greater uncertainties are associated with estimates of the isotopic composition of total dissolved inorganic carbon (δ 13 C SDIC ), the data suggest that two factors—kinetic fractionation and incorporation of respiratory CO 2 —are important in controlling carbon isotope disequilibrium. Where bryozoan species exhibit evidence for disequilibrium in both oxygen and carbon isotope systems ( C. grandis, H. flexuosa ), it is likely that kinetic factors are primarily responsible for observed departures from carbon isotope equilibrium. In contrast, the probable explanation for those species which display evidence for carbon isotope disequilibrium only, is that skeletal carbonate is precipitated from a DIC pool modified by the incorporation of respiratory CO 2 . Differences between the carbon isotope composition of skeletal elements from the same species and co‐existing species living in the same community suggests that significant variations may occur in the extent to which marine DIC and respiratory CO 2 are utilised during calcification. Additional studies of carbon pathways associated with calcification are required to assess the relative effects of kinetic, metabolic, and environmental factors on the carbon isotopic composition of bryozoan skeletal carbonate.

Effects of channel morphology on temporal variation in invertebrate community structure in two North Island, New Zealand rivers - R. T. Fowler; R. G. Death (New Zealand Journal of Marine and Freshwater Research, 2000)
Abundance and species composition of benthic invertebrate communities were investigated in two rivers of contrasting channel form, the Tukipo and Waipawa, in the Southern Hawke's Bay, New Zealand. Monthly collections between December 1995 and December 1996 yielded a total of 89 taxa from the two sites; Deleatidium spp. numerically dominating the braided Waipawa whereas Pycnocentrodes spp., Pycnocentria funerea, Aoteapsyche spp., and Elmidae were most common in the constrained Tukipo. Although disturbance frequency was similar between rivers, the streambed substrates were smaller, and hence less stable in the Waipawa. Number of taxa, total abundance, and community composition changed through time in both rivers. The Waipawa community changed least throughout the year; perhaps because of greater numbers of rare taxa at the Tukipo whereas greater resilience of taxa and community dominance by the mobile generalist Deleatidium spp. in the Waipawa lead to greater constancy. At a broader taxonomic scale, invertebrate communities of the Waipawa were also more similar to communities in two South Island braided rivers (Ashley and Rakaia) than the Tukipo. Thus, although braided river communities may show some similarities throughout New Zealand, the community of the constrained channel was clearly different both in taxonomic composition and temporal change of that composition.

Effects of artificially controlling levels of Lake Taupo, North Island, New Zealand, on the Stump Bay wetland - Prisca Eser; Michael R. Rosen (New Zealand Journal of Marine and Freshwater Research, 2000)
The Stump Bay wetland is part of the South Taupo wetland, situated on the southern coast of Lake Taupo in the central North Island, New Zealand. The water level of Lake Taupo has been artificially controlled since 1941. The present study found that surface and subsurface water levels in the wetland are closely related to each other. These water levels are influenced mainly by rainfall and evapotranspiration (which is seasonal) in areas that are greater than c. 100 m landward from the lake edge, but by the lake level for areas in close proximity to the lake. The wetland is a discharge and/or through‐flow area, and the general flow direction is towards the lake. The time lag for a groundwater rise in the eastern part of the wetland after rainfall was found to be 24 h. The artificial regulation of the lake level has led to a 2 cm rise in annual mean lake levels since 1950. However, when means are calculated for each month separately, the artificially controlled lake level is up to 20 cm higher in the summer than the pre‐controlled summer levels. Significantly higher summer lake levels since 1941 are likely to have caused the observed increase in water levels in the Stump Bay wetland area. Further increases in lake levels are likely to decrease areas of native shrub communities and encourage spreading of the exotic shrub Salix cinerea . Lowering in lake levels may decrease areas of native low‐stature vegetation, but the spreading of native shrub communities may be curbed by competing S. cinerea .

Development and application of a predictive model of riverine fish community assemblages in the Taranaki region of the North Island, New Zealand - Michael K. Joy; Russell G. Death (New Zealand Journal of Marine and Freshwater Research, 2000)
A predictive model of fish community composition using a reference condition approach is proposed for the Taranaki region of New Zealand. The model is used to quantify the effects of barriers on the migration of native fish in the region. Occurrence records of fish in streams without migratory barriers (reference sites) obtained from the New Zealand freshwater fish database were used to establish trajectories of occurrence for each of 12 fish species with altitude. The relative occurrence per site for each of the species was calculated and used as the probability of the presence of that species in that altitudinal range. Comparison of these probabilities with the fauna actually found at a test site expressed as an observed over predicted ratio (O/P) is then used to compare sites to quantify barrier effects on fish communities. In a similar way this process can be used to monitor the effectiveness of fish passes, where present on dams. Independent data from 85 sites sampled over the summer of 1997/98 were used to test the predictive model. As an example of a typical use of the methodology, the effect of a single hydrodam on fish communities is illustrated.

Leaf litter characteristics affect colonisation by stream invertebrates and growth of Olinga feredayi (Trichoptera: Conoesucidae) - John M. Quinn; Brian J. Smith; Gregory P. Burrell; Stephanie M. Parkyn (New Zealand Journal of Marine and Freshwater Research, 2000)
The influences of leaf characteristics on stream invertebrate communities were investigated to improve the basis for selecting plants for riparian management to enhance stream invertebrate abundance and biodiversity. Invertebrate colonisation of leaves of five native and five exotic riparian plants were compared over 4 months in field experiments in a New Zealand pasture stream and adjacent channels, and laboratory experiments were carried out on the leaf preferences and effects on growth of the larvae of Olinga feredayi . Plastic strips and leaves enhanced average invertebrate species richness on tiles in streamside channels by 35 and 68%, and density by 50 and 140%, respectively, indicating that both food and physical habitat contribute to leaf pack effects of increased invertebrate abundance and species richness. Densities of total invertebrates and collector‐browsers on leaf packs after 15 days in the streamside channels were positively correlated with leaf % leaching and microbial respiration, and negatively correlated with leaf carbon: nitrogen (C:N) ratio and toughness. Filter‐feeding invertebrates showed opposite relationships. Growth of O. feredayi larvae on conditioned leaves was negatively correlated with initial leaf C:N ratio, and positively correlated with colonisation preferences of larvae presented with a range of conditioned leaves. These findings provide improved guidance as to which riparian plants to select to optimise the benefits of litter inputs for stream invertebrates.

The Wairarapa Coastal Current - Stephen M. Chiswell (New Zealand Journal of Marine and Freshwater Research, 2000)
A new name is proposed for the relatively cool, fresh, northwards‐directed flow along the Wairarapa coast of New Zealand. Data from two research cruises plus historical hydrocast dam are used to show that the water within this current is modified subtropical water with sources likely to be the Southland and D'Urville currents. This current has previously been known as the Canterbury Current or as an extension of the Southland Currer t, but because of its source and location, a better name is the Wairarapa Coastal Current. One‐month‐long current meter records made off the Wairarapa coast show flow continuously to the north during February 1998. Volume transports within the Wairarapa Coastal Current in February 1998 were c. 1.6 Sv off Cape Palliser, diminishing northwards as the current becomes entrained into the East Cape Curren:.

Toxic marine epiphytic dinoflagellates, Ostreopsis siamensis and Coolia monotis (Dinophyceae), in New Zealand - Lesley Rhodes; Janet Adamson; Toshiyuki Suzuki; Lyn Briggs; Ian Garthwaite (New Zealand Journal of Marine and Freshwater Research, 2000)
Ostreopsis siamensis and Coolia monotis (Ostreopsidaceae) are newly recognised additions to New Zealand's toxic marine microflora and occur epiphytically on seaweeds throughout subtropical New Zealand. O. siamensis “blooms” during summer, becoming freely motile; it tolerates temperatures of 15–25°C and salinities of 28–34 ppt. C. monotis also occurs in sediments in Nelson/ Marlborough and Stewart Island, at 10–30°C and salinities of 20–34 ppt. O. siamensis from Rangiputa, Northland, produced activity equivalent to ≤0.3 pg cell~’ of palytoxin as measured using a haemolysis‐neutralisation assay, and cell extracts killed mice by intraperitoneal injection. Extracts of oysters fed with O. siamensis did not kill mice. C. monotis , from Rangiputa, produced compounds in extracts of cells and of culture supernatant which were also toxic to mice and which are currently being characterised. C. monotis caused positive sodium channel activity in neuroblastoma assays; O. siamensis was cytotoxic, and irreversibly suppressed cell firing in hippocampal brain slices. Lectin probes differentiated the two species, suggesting differential sugar moieties at their cell surfaces.

Thermal tolerances of two stream invertebrates exposed to diumally varying temperature - Timothy J. Cox; J. Christopher Rutherford (New Zealand Journal of Marine and Freshwater Research, 2000)
For two key New Zealand freshwater invertebrates (the mayfly Deleatidium autumnale and the snail Potamopyrgus antipodarum ) the upper thermal tolerances were measured in the laboratory under both constant and diumally varying temperatures. At constant temperature 50% mortality in 96 h ( const LT 50 ) occurred at 24.2 ± 0.9°C for mayflies and 31.0 ± 0.6°C for snails: values similar to previously published estimates (Quinn et al. 1994). For diurnally varying temperatures (daily amplitude 10°C) 50% mortality occurred when the daily mean temperature was 21.9 ± 0.7°C (mayflies) and 28.6 ± 0.4°C (snails) which is c. 10% (2.5 ± 1.3°C) lower than the const LT 50 . Conversely, 50% mortality occurred when the daily maximum temperature was 26.9 ± 0.7°C (mayflies) and 33.6 ± 0.4°C (snails) which is c. 10% (2.5 ± 1.3°C) higher than the const LT 50 . Many published temperature limits for stream organisms are derived from constant temperature experiments. Our results indicate that such limits should be applied to a temperature midway between the daily average and the daily maximum of a diurnal profile.

Glossary of aquatic habitat inventory terminology. Compiled by Neil B.Armantrout. Published in 1998 by American Fisheries Society. 150 p. ISBN 1–888569–11–5. Price: US$33.00 (available from: APS Publication Fulfillment, P. O. Box 1020, Sewickley, PA 15143, United States).Studying temperate marine environments— a handbook for ecologists. Edited by MichaelKingsford and ChristopherBattershill. Published in 1998 by Canterbury University Press, Private Bag 4800, Christchurch, New Zealand (email: m.bradstock@cup.canterbury.ac.nz). 344 p., limpbound. ISBN 0–908812–54‐X. Price: NZ$49.95. - Neil Deans; Robert G. Wear (New Zealand Journal of Marine and Freshwater Research, 2000)

Influences of leaf toughness and nitrogen content on in‐stream processing and nutrient uptake by litter in a Waikato, New Zealand, pasture stream and streamside channels - John M. Quinn; Gregory P. Burrell; Stephanie M. Parkyn (New Zealand Journal of Marine and Freshwater Research, 2000)
The factors influencing in‐stream disintegration and uptake of dissolved nutrients by leaves were investigated to improve the basis for selecting plants for riparian management. Leaves from five introduced and five New Zealand native plants were studied in 12 streamside channels and a natural stream. Fallen, air‐dried leaves were tethered in packs attached to tiles in the channels and stream, and measured for mass loss, nitrogen and phosphorus uptake, toughness (by penetrometry), respiration rates, carbon: nitrogen (C:N) ratios, and macroin‐vertebrate communities after 7, 15, 28, 56, 126, and 226 days. Initial leaching over 2 days reduced mass by 8–32%, and microbial respiration could account for up to 23–93% (median = 43%) of dry mass (DM) lost over the first 56–126 days. First order mass loss rates (k, day ‐1 ) varied 14‐fold, from ‐0.0028 day ‐1 for Knightia excelsa to ‐0.039 day ‐1 for Juglans nigra , and were correlated most strongly with leaf toughness after 7 days in stream water ( r = ‐0.84). Leaf packs in Mangaotama Stream, that were more rapidly colonised by invertebrates and exposed to frequent flow disturbances, had 3‐ to 5‐fold higher mass loss rates than those in the streamside channels. The 12‐fold variation amongst leaf species in mean uptake rate of dissolved reactive phosphorus (DRP), and the 6‐fold variation in mean nitrate uptake were correlated with k ( r = ‐0.78 and ‐0.92 for DRP and NO 3 ‐N, respectively), respiration after 7 days ( r = 0.80 and 0.84) and toughness after 2 days of leaching ( r = ‐0.77 and ‐0.82). These findings improve the basis for selecting riparian plant species to optimise in‐stream nutrient retention and invertebrate food supply in streams with different abilities to retain litter fall. For example, riparian plants with soft, N‐rich, leaves are recommended to enhance the detrital energy base of streams where frequent spates flush leaf litter down stream, whereas a wider variety of plants and leaf types will be suitable for riparian planting for this purpose along highly retentive streams.

First record of pre‐settlement juvenile bluenose, Hyperoglyphe antarctica , from New Zealand - C. A. J. Duffy; A. L. Stewart; R. Yarrall (New Zealand Journal of Marine and Freshwater Research, 2000)
Epipelagic juvenile bluenose, Hyperoglyphe antarctica (Carmichael 1818), are recorded from New Zealand for the first time. Two specimens were collected beneath flotsam nearNga Motu/Sugar Loaf Islands, west coast North Island in September 1996, and at least 20 were found inside a piece of trawl net drifting east of Cape Kidnappers, east coast North Island in September 1997. Live specimens between 65 and 87.3 mm standard length were cryptically coloured and were able to change their body colour from dark coppery‐bronze to blue. Freshly dead specimens lacked the thick mucous coat found in juveniles of other Hyperoglyphe species known to associate with jellyfish. We suggest that H. antarctica recruitment may be higher along the lower east coast North Island because of retention of flotsam‐associated juveniles in the East Cape and Wairarapa Eddies, and that juveniles spawned off south‐east Australia may reach New Zealand in the Tasman Current.

New Zealand's National River Water Quality Network: Long‐term trends in macroinvertebrate communities - Mike R. Scarsbrook; Ian K. G. Boothroyd; John M. Quinn (New Zealand Journal of Marine and Freshwater Research, 2000)
Aquatic macroinvertebrates were sampled annually at 66 sites of the National Rivers Water Quality Network (NRWQN) from 1989 to 1996. At each site, temporal trends in number of taxa, total abundance, Macroinvertebrate Community Index (MCI), the quantitative version of MCI (QMCI), number and percent of Ephemeroptera, Plecoptera, and Trichoptera, Shannon's Diversity Index (H'), Jaccard's similarity index, and Bray‐Curtis similarity index were analysed using non‐parametric Spearman rank correlations. Sixty‐nine significant ( P 0.10) trends were found out of a total of 594 analyses. There were 27 positive trends (i.e., showing increases in invertebrate community measures through time) and 42 negative. MCI and Jaccard's Index exhibited the greatest number of trends (13), and Shannon's diversity the least (1). A number of sites (8) showed a significant trend of decreasing taxa richness, particularly pollution‐sensitive Ephemeroptera, Plecoptera, and Trichoptera (EPT). However, MCI values, which are strongly linked to numbers of EPT taxa, had the highest number of positive trends (12), with only one site showing a negative trend. Overall the trend in MCI scores was particularly strong for “baseline” sites, and less so for “impact” sites. The percentage of baseline sites with MCI scores indicative of clean water increased from 3% in 1989 to 46% in 1996. At two sites trends in MCI and number of EPT taxa gave conflicting signals. Regional patterns were apparent, with trends in MCI in particular being more common in the east and lower half of the North Island, and the lower half of the South Island than in other areas. Observed trends in some macroinvertebrate community measures, particularly MCI, coincided with reported general improvements in water quality.

Predicting the effects of time‐varying temperatures on stream invertebrate mortality - Timothy J. Cox; J. Christopher Rutherford (New Zealand Journal of Marine and Freshwater Research, 2000)
Stream managers often need to predict the impacts of high and time‐varying temperature on key stream invertebrates. A simplified model has been developed and calibrated using mortality observations made at constant temperature for two important New Zealand stream invertebrates: the snail Potamopyrgus antipodarum and the mayfly Deleatidium autumnale . A close fit was obtained for Deleatidium but Potamopyrgus showed evidence of acclimation during the 96‐h tests. The model successfully predicted the mortality observed when temperature varied diurnally by ±5°C in seven experiments but over‐estimated mortality in the eighth. The experiments used to calibrate and test the model were performed on test animals collected in winter (April‐June) and acclimated at 16–17°C. The model was less successful at predicting mortality on Deleatidium collected in summer (December‐January) and/or acclimated at 21–22°C. The likely reason is that the model, calibrated using winter data, does not account for summer acclimation.

Features of 3‐dimensional barotropic and baroclinic circulation in the Hauraki Gulf, New Zealand - K. P. Black; R. G. Bell; J. W. Oldman; G. S. Carter; T. M. Hume (New Zealand Journal of Marine and Freshwater Research, 2000)
Predominant features of barotropic and baroclinic circulation and mixing in the Hauraki Gulf on New Zealand's north‐east coast are described using measurements and 3‐dimensional numerical model simulations. Circulation in the Hauraki Gulf is strongly 3‐dimensional with a primary dynamical balance between surface wind stress and the associated pressure gradients against the land. This leads to persistent up/downwelling and surface manifestations in sea surface temperature patterns which are shown to vary systematically and markedly with wind direction and stratification intensity. A high degree of correspondence between a baroclinic numerical model and measured temperature and nitrate concentrations indicated that many of the observed spatial patterns could be largely explained by the interaction of the wind and tidal circulation with the unique morphology of the Gulf. After strong southeasterly winds, local responses operated in conjunction with the regional “capping” mechanism described by Sharpies (1997) of downwind surface water intrusion from the shelf into the Gulf. However, the morphology acts to enhance local upwelling causing bottom waters to be injected into the surface layers which disrupts the “cap”. The headlands and islands play an additional vertical mixing role by presenting bathymetric variability leading to the formation of upwelling jets in the core of eddies forming during ebb and flood tides. By introducing bottom waters into the upper water column and acting to over‐turn the water body, up/downwelling is an important mechanism for mixing and biological productivity which could vary systematically within the Gulf in response to seasonal and interannual variability in the upwelling patterns. Persistent south‐east winds above a threshold of 10–12 m s ‐1 were found to initiate breakdown of seasonal temperature stratification in the Gulf, with complete breakdown after 3 days during a cyclone with 8–23 m s ‐l winds. Vertical eddy diffusivity increased from 0.0015 to 0.04 m 2 s ‐1 as the cyclone strengthened.

Macroscopic intersexuality in salmonid fishes - M. T. Kinnison; M. J. Unwin; F. Jara (New Zealand Journal of Marine and Freshwater Research, 2000)
The occurrence of individual salmonids with macroscopically identifiable, simultaneous male and female gonads is an uncommon reproductive disorder. Individual specimens have been described, but no larger synthesis of the condition has been made. We first describe two simultaneous in‐tersexual Pacific salmon ( Oncorhynchus spp.) specimens, encountered during rearing operations in New Zealand and Chile, confirming that the phenomenon occurs beyond the natural range of the genus. A review of these and other isolated specimens within the Salmonidae ( Oncorhynchus, Salmo, Salvelinus, Coregonus, Thymallus ) suggests that the disorder takes at least two distinct anatomical patterns, which we call lobular and mosaic. These are consistent with differences in either the degree or onset time of aberrant development from protogynous or neutral gonadal primordia. The disorder has a low natural incidence (one in several thousand), but the extensive use and study of salmonids makes it likely that natural macroscopic hermaphrodites will be encountered regularly. Isolated specimens have been attributed to environmental contamination, but their widespread occurrence suggests they are primarily a natural phenomenon.

Inundated floodplain gravels in a stream with an unstable bed: Temporary shelter or true invertebrate refugium? - C. D. Matthaei; C. R. Townsend (New Zealand Journal of Marine and Freshwater Research, 2000)
At near‐peak flow of a large flood in a New Zealand stream, we took 10 Surber samples in calm, shallow areas of an inundated flood plain. The next day, when discharge was still high enough to cause bed movement in the main channel but the flood plain had dried out again, we collected 10 sediment samples in the dry flood plain. Invertebrate taxon richness in during‐flood samples was 83% of that found in the main channel after a period of stable flow, and total invertebrate densities were 10% of densities during stable conditions. Taxon richness, total densities, and densities of the four taxa most common in the benthos of the river were significantly lower in the dry flood plain than in during‐flood samples, implying that many invertebrates left these patches during drying. Nevertheless, mean total invertebrate densities in the dry flood plain were still 37% of during‐flood values. We conclude that inundated floodplain gravels provided temporary shelter for lotic invertebrates during the flood, but several animals were trapped as the flood plain dried, and those that managed to return to the baseflow channel were still exposed to bed‐moving shear stresses. We doubt that floodplain gravels can act as true invertebrate refugia in our study river, primarily because of the unstable nature of its sediments.

Source and transport of trace metals in the Hatea River catchment and estuary, Whangarei, New Zealand - Jenny G. Webster; Kevin L. Brown; Kerry S. Webster (New Zealand Journal of Marine and Freshwater Research, 2000)
A survey of Cu, Pb, Zn, Cr, and As concentrations in bed sediment, fresh waters, storm waters, and suspended particulate matter (SPM) has been undertaken in the Hatea River catchment, Whangarei, New Zealand. The most recently deposited sediment in the Hatea River estuary has elevated levels of Cu, Pb, and Zn, derived from tributaries draining the more densely‐populated western side of the catchment, city stormwater drains, and Cu‐bear‐ing antifoulants used in the marina. All trace metals were transported in both “dissolved” and particulate form in the freshwater tributaries. However, an estimated loading of metal transported by the lower Hatea River under different flow regimes indicated that trace metals were predominantly conveyed by coarse (>0.45 μm) SPM during the periods of highest river flow. Of the trace metals studied, Pb showed the strongest association with coarse SPM and the greatest potential for accumulation in estuarine sediment, demonstrating little tendency to be leached from sediment under simulated estuarine conditions.

Review of New Zealand bullseyes (Perciformes: Pempheridae) - Randall D. Mooi (New Zealand Journal of Marine and Freshwater Research, 2000)
The known pempherid fauna of New Zealand comprises two species: Pempheris adspersa Griffin, endemic to the north‐eastern shores of North Island; and P. analis Waite, found in the Kermadec Islands as well as Norfolk Island, Lord Howe Island, and the east and west coasts of Australia. Pempheris adspersa differs from P. analis in having: some interorbital scales cycloid (versus all interorbital scales ctenoid), usually 3 or more predorsal scales cycloid which often form a mesial line of cycloid scales (versus rarely 4 or fewer predorsal scales cycloid), lateral‐line scales 56–68 but rarely more than 66 (versus 63–77, rarely fewer than 65), and scales below lateral line 18–24 but rarely more than 22 (versus 22–27). A principal components analysis differentiates the two species with only slight overlap. Reports of P. compressa from New Zealand are erroneous; descriptions of P. compressa and P. adspersa have been confused in the literature. Pempheris compressa differs from P. adspersa in having: anal fin dusky along entire length (versus tips of first 4–5 anal‐fin rays black), gular region scaled (versus unsealed), segmented anal‐fin rays 35–40 (versus 29–35), head depth 36–41 % of standard length (SL) (versus 31–38%), and body depth 44–52% of SL (versus 38–46%). A principal components analysis clearly differentiates the two species.

Links between climate variation and the year class strength of New Zealand hoki ( Macruronus novaezelandiae ) Hector - Mary E. Livingston (New Zealand Journal of Marine and Freshwater Research, 2000)
Hoki ( Macruronus novaezelandiae ) Hector year class strength (YCS) varies substantially from year to year. In this study, potential links between hoki YCS estimates for western and eastern stocks, and time series of the Southern Oscillation Index (SOI), satellite sea surface temperatures (SST), synoptic weather patterns, depth of the mixed layer (western stock only), and wind speeds are explored. The results indicate that favourable recruitment in the western stock is correlated with a negative SOI and associated conditions such as lower SSTs, early onset of deep water mixing and synoptic weather patterns that result in a higher incidence of southwest (SW) flow. Favourable recruitment in the eastern stock appears to be correlated with periods of westerly flow, particularly from the SW, but also the north‐west (NW). Regression studies showed that when inter‐correlation was minimised, 95% of the variation in YCS of the western stock was explained by four variables—SOI in autumn, the onset of winter mixing, SST in spring, and NW spring weather patterns. In the eastern stock, 88% of the variation in YCS was explained by SW and NW winter weather patterns and the average speed of SW winds in winter through Cook Strait. Although the underlying mechanisms are not proven, the climate variables which appear to be linked to favourable recruitment for both western and eastern stocks, also favour upwelling and the physical transportation of larval hoki from the spawning grounds into their respective inshore nursery areas.

Analysis of relationships between maximum depth limits of aquatic plants and underwater light in 63 New Zealand lakes - A‐M. Schwarz; C. Howard‐Williams; J. Clayton (New Zealand Journal of Marine and Freshwater Research, 2000)
Data from 63 New Zealand lakes were analysed to determine latitudinal and other patterns in the relationship between water clarity and the maximum recorded depths for submerged aquatic macrophytes (Z c ). Vascular plants were encountered at Z c in 25% of the 63 lakes investigated. Characean algae extended to greater depths and occurred at Z c in 71% of the lakes, with a maximum depth of 34.4 m. There was a difference between North and South Island lakes, in values of Z c predicted from water clarity, that was not consistent with their latitudinal displacement. In clear North Island lakes, Z c was predicted to be less than in lakes of similar water clarity in the South Island and to reach an asymptotic maximum depth of 21 m. In contrast, the relationship between water clarity and Z c in South Island lakes was linear, with Z c of more than 30 m in some lakes at c. 2% of subsurface irradiance. Although the availability of light explained depth limits in most South Island lakes, other factors (e.g., grazing impact from freshwater crayfish) appear to be contributing to the shallower Z c in clear North Island lakes.

Synthesis of extreme wave climate for the Canterbury Bight, New Zealand - G. H. Macky; A. I. McKerchar; A. K. Laing; G. S. Carter; A. M. Chater (New Zealand Journal of Marine and Freshwater Research, 2000)
Numerical models of the marine wind field and wave generation offer a technique for estimating the severity of extreme wave events. Measured and modelled waves in the Canterbury Bight, New Zealand, were used to examine the hypothesis that extreme conditions can be more confidently estimated by modelling the wave climate over a decade than by analysing shorter measured records. The meteorological conditions causing high waves in the Canterbury Bight were examined by inspecting wind measurements at Christchurch Airport and wave buoy measurements made in 1983–85 near the Rakaia River mouth. Although the arrival of high waves was sometimes associated with wind changes at the airport, peak wave heights generally occurred at least several hours after such wind changes and were associated with south‐westerly or southerly winds in the Bight and a depression south‐east of the South Island. Wave conditions at the buoy site for 1980–89 were modelled using marine winds obtained from a global circulation model, running a wave generation model for the seas around New Zealand, and then applying a refraction model. The decade modelled included two El Niño events and one La Niña event, and the ocean wind climate should therefore have been reasonably representative of the long‐term range of conditions. The model results were verified against the buoy measurements. Estimates of extreme wave heights were then made from 10 years of modelled record and also the measured buoy record. Application of the Gumbel distribution to the monthly maxima gave a significant wave height of 9.5 m for the wave event with an annual exceedance probability of 1 in 50. Model predictions indicate that the most severe waves arrive in the Bight from due south. Estimates of extremes from the measurements and model hindcast were close, indicating that the hindcast represents a population of events similar to those measured.

Transport and attenuation of bacteria and bacteriophages in an alluvial gravel aquifer - L. W. Sinton; M. J. Noonan; R. K. Finlay; L. Pang; M. E. Close (New Zealand Journal of Marine and Freshwater Research, 2000)
The relative attenuation of rhodamine WT dye, two strains of Escherichia coli, Bacillus subtilis endospores, and the F‐RNA bacteriophage MS2 in an alluvial gravel aquifer was investigated in two tracing experiments at Burnham, near Christchurch, New Zealand. A simulated concentration curve was fitted to the observed breakthrough curves using the contaminant transport model AT123D, by optimising hydraulic conductivity (K), longitudinal dispersivity (α x ), and a removal constant (λ) (which includes die‐off and physical removal processes) with the Parameter Estimation (PEST) optimisation routine. When comparing the parameters, the hydraulic conductivity was converted to velocity (V). The V ranking was E. coli 2690 > B. subtilis endospores > rhodamine WT in Experiment 1 and E. coli J6–2 > phage MS2 > rhodamine WT in Experiment 2. These rankings are consistent with the concept of pore size exclusion, whereby larger particles are preferentially transported in the larger interconnected pores where water velocities are higher. The longitudinal dispersivity (α x ) rankings were consistent with pore size exclusion in Experiment 1, and broadly consistent in Experiment 2. Of the two parameters, V is considered to provide the more reliable result, because it is easier to determine peak position in time than peak height. Little useful information could be derived from the λ values in our study, because of high levels of uncertainty associated with determining peak heights, particularly in Experiment 1. Overall, the curve fits were better in Experiment 2, because of a greater number of bores and observations. Although this complicated between‐experiment comparisons, an overall retardation (R) ranking of rhodamine WT > phage MS2; B. subtilis endospores > E. coli J6–2 > E. coli 2690 is broadly consistent with pore size exclusion. Overall, our study showed that the application of the AT123D model to the observed velocities of the tracer curves demonstrated an effect consistent with pore size exclusion.

Sensitivity of aquatic life stages of Xanthocnemis zealandica (Odonata: Zygoptera) to azinphos‐methyi and carbaryi - Sonke Hardersen; Steve D. Wratten (New Zealand Journal of Marine and Freshwater Research, 2000)
The susceptibility (48‐h LC 50 values) of aquatic life stages of Xanthocnemis zealandica McLachlan to azinphos‐methyi and carbaryi was investigated. The LC50 values of azinphos‐methyi did not correlate with instar. The most susceptible stage was instar 7 (LC 50 value: 26.6 ppb), and the least susceptible were instars 2 (LC50 value: 50.2 ppb) and 13 (LC 50 value: 45.1 ppb). In contrast, LC 50 values for carbaryi were positively related to larval instar (instar 2: LC 50 value: 156.6 ppb; instar 13: LC 50 value: 760 ppb). Damselfly eggs were exposed to insecticide solutions (azinphos‐methyi: control, 0.04, 0.4, 4, and 40 ppb; carbaryi: 0.6 b and 6, 60, and 600 ppb) and hatching success evaluated. Only carbaryi at 600 ppb reduced hatching success significantly. Although the investigation on eggs was carried out at a higher temperature than the LC 50 experiments it can be concluded that the egg stage is more resilient to both insecticides than the larval stages.

Three recently recorded Ostreopsis spp. (Dinophyceae) in New Zealand: Temporal and regional distribution in the upper North Island from 1995 to 1997 - F. H. Chang; Y. Shimizu; B. Hay; R. Stewart; G. Mackay; R. Tasker (New Zealand Journal of Marine and Freshwater Research, 2000)
Three species of epiphytic dino‐flagellates— Ostreopsis siamensis, O. lenticularis , and O. ovata have recently been found on both the east and west coasts of the upper North Island, New Zealand. The morphological differences of all three Ostreopsis spp. have been studied with both light and scanning electron microscopes. Detailed studies of the inner face of the thecal wall of Ostreopsis siamensis revealed two types of trichocyst pores: small, simple pores and large multipore structures. The multipore structures apparently have not been previously reported. Surveys conducted during the period from November 1995 to April 1997 showed that all three Ostreopsis spp. were fairly widespread in northern New Zealand, and all three species were found to occur south of 35°S latitude. Cell concentrations of Ostreopsis spp. in summer were substantially higher than in early spring. There was also a clear regional difference in distribution; cell concentrations of the dominant species, O. siamensis , were greatest in Rarawa and Tokerau on the north‐east coast. Other less abundant epiphytic species recorded during the same period included Prorocentrum lima, P. compressum , and Coolia monotis . These species were generally more sporadic in distribution than Ostreopsis spp.

Variability of water masses through the Mernoo Saddle, South Island, New Zealand - Andrew G. P. Shaw; Ross Vennell (New Zealand Journal of Marine and Freshwater Research, 2000)
The Mernoo Saddle is situated c. 100 km east of Banks Peninsula, Canterbury, New Zealand at 44°S 174°E. The Saddle separates the South Island of New Zealand from an underwater ridge known as the Chatham Rise. The Rise acts as a partial barrier to the flow of the subantarctic surface water mass (SAW) and the subtropical surface water mass (STW), which are part of the global Subtropical Front extending around the Southern Ocean. This study examined the variability of the water masses flowing through the Mernoo Saddle using a 3‐year data set of Advanced Very High Resolution Radiometer (AVHRR) Sea Surface Temperature (SST) imagery. This investigation revealed that SAW extended north through the western edge of the Mernoo Saddle for most of the year, however in winter and early spring a southward extension of STW was observed.

Microphytobenthic communities of subtidal locations in New Zealand: Taxonomy, biomass, production, and food‐web implications - Paul A. Gillespie; Paul D. Maxwell; Lesley L. Rhodes (New Zealand Journal of Marine and Freshwater Research, 2000)
Diatom mats dominated by large sig‐moid, raphid species of the genus Gyrosigma (Naviculaceae) and, in some instances, the tube‐former, Berkeleya rutilans (Naviculaceae) were observed in the semi‐enclosed coastal waters (depths 6–20 m) of Tory Channel, Marlborough Sounds, New Zealand. The latter species, not previously observed in New Zealand, is generally associated with intertidal environments where light intensities are relatively higher than subtidal locations. Its presence imparted a filamentous nature to the mat that may play a role in maintaining the integrity of the sediment/water interface. Sediment chlorophyll a concentrations ranged from c. 20 to 200 mg m ‐2 . Microphytobenthic (MPB) contributions to the total (benthic + planktonic) chlorophyll a equated to 92, 89, and 84% at depths of 8, 16, and 20 m, respectively. Oxygen production in intact cores often exceeded consumption (e.g., by up to 2.5 mmol m‐2h ‐1 ) under near‐m situ conditions of light (8–30 μmol m ‐2 s ‐1 ). The feeding strategies of major components of the benthic macroinvertebrate fauna were used to identify possible pathways for utilisation of MPB production. MPB communities of more exposed subtidal locations in Tasman Bay were generally less dense and comprised of different species dominated by Pleurosigma amara and/or Paralia marina . We conclude that microalgal communities inhabiting the soft sediments in these regions can provide an important contribution to the benthic food web.

Induced spawning and early ontogeny of New Zealand freshwater eels {Anguilla dieffenbachii and A. australis ) - P. Mark Lokman; Graham Young (New Zealand Journal of Marine and Freshwater Research, 2000)
Knowledge on the reproductive biology of New Zealand freshwater eels ( Anguilla australis Richardson and A. dieffenbachii Gray) is limited to changes associated with gametogenesis in the adults; details pertaining to embryonic and larval development are not available, but are of obvious benefit for a better understanding of the eel life history and for artificial propagation programmes, whether for aquaculture or conservation purposes. Therefore, eels were artificially matured and eggs fertilised with sperm from either species to investigate early ontogeny. Only eggs from A. australis hatched successfully after c. 45 h of incubation at room temperature, yielding larvae of c. 2.5 mm in length. Larvae survived for up to 5 days, by which time they had attained a length of 5.3 mm. Scanning electron microscopy of 1‐ and 2‐day‐old larvae revealed the presence of prominent free neuromasts on the head and along the flanks. Although hatching of New Zealand eels was achieved for the first time, it is strongly recommended that hormone treatment be initiated immediately following capture, well before ovarian atresia starts.

Anisakis (Nematoda) in some New Zealand inshore fish - D. A. Wharton; M. ‐L. Hassall; O. Aalders (New Zealand Journal of Marine and Freshwater Research, 1999)
The prevalence, intensity, abundance, and density of Anisakis larval infection of four species of New Zealand fish and one species of squid were determined. In order of intensity of infection these were: barracouta (Thyristes atun) , tarakihi (Nemadactylus macropterus) , red cod (Pseudophycis bachus) , red gurnard (Chelidonichthys kumu) , and arrow squid (Nototodarus solanii) . Some data on infections in monkfish (Kathetostoma giganteum) are also presented. There was no evidence of postmortem migration of larvae in red cod, red gurnard, or barracouta. The larvae did excapsulate postmortem and the excapsulation was less in fish kept on ice. The majority of larvae were associated with the visceral organs and membranes (98.5% or more of the total worm burden). However, a proportion of all fish species examined had small numbers of larvae in the fillets and these may pose a risk to human health.

New species of dictyoceratid sponges from New Zealand: Genus Ircinia (Porifera: Demospongiae: Dictyoceratida) - Steve de C. Cook; Patricia R. Bergquist (New Zealand Journal of Marine and Freshwater Research, 1999)
This paper is the third in a series revising the taxonomy of New Zealand dictyoceratid sponges (phylum Porifera, class Ceractinomorpha, order Dictyoceratida). Only one species of Ircinia has previously been described from New Zealand, Ircinia novaezealandiae Bergquist, 1961. Six new species of Ircinia are added to New Zealand's known fauna. The genus Ircinia contains in excess of 40 published species worldwide, although the integrity of some of these is uncertain, often because of poor diagnoses. The diagnoses of new species reported here provide a model for the morphological descriptions of future species. The subdivision of Ircinia is also considered.

Stock structure of southern blue whiting ( Micromesistius australis) in New Zealand waters - Stuart Hanchet (New Zealand Journal of Marine and Freshwater Research, 1999)
Data on the reproduction, growth, and morphometric characteristics of southern blue whiting (Micromesistius australis Norman) were examined to determine its stock structure in New Zealand waters. Consistent differences in the size distribution of fish, and in the timing of spawning were found between spawning grounds on the Bounty Platform, Pukaki Rise, Auckland Islands Shelf, and Campbell Island Rise. Significant differences in morphometric characteristics were found between fish from the Bounty Platform, Pukaki Rise, and Campbell Island Rise and significant differences in growth rates were found between the Bounty Platform and Campbell Island Rise. The results provide strong evidence that fish return to spawn on the grounds to which they first recruit, and suggest that the four areas should be assessed and managed as separate stocks.

A new deep sea barnacle, Tetrachaelasma tasmanicum sp. nov. (Cirripedia: Balanomorpha) from the South Tasman Rise, South Pacific Ocean - John S. Buckeridge (New Zealand Journal of Marine and Freshwater Research, 1999)
A new deep sea balanomorph, Tetrachaelasma tasmanicum sp. nov., is described. This new record is based on numerous disarticulated plates, from dredge samples around deep‐sea seamounts on the South Tasman Rise. This is the deepest known occurrence of the Balanomorpha, and the first record of Tetrachaelasma from the Pacific realm. An overview of the biogeography, including aspects of the palaeontology of deep sea balano‐morphs is provided. A map showing station localities and a list of deep sea cirripedes recovered from the South and East Tasman Rise during the 1995 Rig Seismic cruise, are included.

Summer distribution patterns of the backswimmer, Anisops wakefieldi (Hemiptera: Notonectidae), in a New Zealand pond - John J. Gilbert; Carolyn W. Burns; Caroline C. Gilbert (New Zealand Journal of Marine and Freshwater Research, 1999)
The relative abundance of different‐sized Anisops wakefieldi in a small, fishless pond was determined from sweep‐net samples taken along one open‐water and two shoreline transects at noon on two dates, and at noon and midnight on a third date. During the day, large individuals occurred only along the shore, whereas smaller ones occurred both along the shore and in open water. At night, large individuals also occurred in the open water. The diurnal size‐class segregation suggests that young individuals migrate into less preferred, open water to avoid interference and cannibalism from larger individuals. The shoreline may be preferred during the day because it provides greater food resources or a refuge from visually feeding avian predators. Laboratory experiments in containers with floating aquatic plants at one end complemented the field data. When alone, both small and large A. wakefieldi sought cover during the day and moved into open water at night. During the day, the presence of large individuals induced small ones to move into open water. The results of this study on a notonectid population are consistent with some earlier ones in demonstrating that interactions between large and small size classes may lead to pronounced spatial segregation of size classes, and show for the first time that spatial distributional patterns during the day and night may be very different.

Minimal impact from long‐term dredge spoil disposal at a dispersive site in Tasman Bay, New Zealand - Rodney D. Roberts; Barrie M. Forrest (New Zealand Journal of Marine and Freshwater Research, 1999)
The effects of dredge spoil disposal on contaminant concentrations and benthic macrofauna were examined at a shallow marine disposal site used for c. 20 years. The site had received c. 50 000 m 3 yr ‐1 of maintenance dredgings annually, from the Port of Nelson. Port sediments were contaminated to varying degrees with some trace metals, organo‐chlorine pesticides, polychlorinated biphenyls, and polycyclic aromatic hydrocarbons. They showed mildly elevated toxicity in laboratory bioassays, and their macrofauna was dominated by small‐bodied polychaetes. Despite this, there was very little indication of impact in the spoil disposal area. The disposal area, spoil spreading zone and control sites were all similar in terms of sediment contaminants, sediment toxicity, neogastropod imposex, and macrofauna. The lack of discernible impact is probably because of the dynamic sedimentary environment in the disposal area, which disperses dumped dredgings and mixes them with ambient sediment.

Water quality of a lowland stream in a New Zealand dairy farming catchment - Robert J. Wilcock; John W. Nagels; Harvey J. E. Rodda; Michael B. O'Connor; Bruce S. Thorrold; James W. Barnett (New Zealand Journal of Marine and Freshwater Research, 1999)
A small stream in a predominantly dairying catchment in the Waikato region of New Zealand was monitored for 2 years at three sites. Total nitrogen (TN) concentrations were up to 7.09 g m ‐3 in winter, with the bulk comprising nitrate nitrogen (NO ‐ 3 ‐N). During summer NO ‐ 3 ‐N was near zero and TN mostly comprised organic nitrogen. Maximum concentrations of total phosphorus (TP) and dissolved reactive phosphorus (DRP) were 1.64 and 0.555 g m ‐3 , respectively, and peaks coincided with spring and autumn applications of phosphorus fertiliser. Ammoniacal nitrogen concentrations exceeded 1 g m ‐3 on several occasions and mean concentrations at the three sites were 0.165–0.272 g m ‐3 . Faecal coliform and enterococci bacteria concentrations were 64–26000 and 7–23000 cfu per 100 ml, respectively. Specific yields of TN and NO ‐ 3 ‐N (35.3 and 30.7 kg ha yr ‐1 , respectively) were much greater than any previously reported for New Zealand pasture catchments, whereas TP and DRP yields (1.16 and 0.54 kg ha yr ‐1 , respectively) were more in accord with other studies. Greater use of land treatment of liquid wastes will reduce stream inputs of faecal organisms, NH 4 ‐N and P.

Water and sediment chemistry of a wetland treating municipal wastewater - Catherine Chagué‐Goff; Michael R. Rosen; Mirjam Roseleur (New Zealand Journal of Marine and Freshwater Research, 1999)
The effects of wastewater discharge in an artificially confined wetland, Turangi land treatment facility, New Zealand, were investigated by measuring the changes in water and sediment chemistry in the land treatment facility. Analysis of surface water shows that the treatment facility is effective at removing BOD 5 (85%), but not NH 4 ‐N, SO 4 , PO 4 ‐P, and total suspended solids. Surface flow measurements indicate that the effluent flows through the confined wetland in less than a day. The retention time is too short to allow exchange between wetland vegetation and effluent, thus preventing efficient contaminant removal. The change in land use c. 30 years ago associated with the construction of the land treatment facility is reflected in a change in stratigraphy and sediment chemistry. Elevated sulphur and zinc concentrations in sediments are attributed to sewage effluent discharge, and indicate that soil uptake is taking place.

Shore‐level induced variations in condition and feeding of the mussel Perna canaliculus from the east coast of the South Island, New Zealand - Islay D. Marsden; Mark A. Weatherhead (New Zealand Journal of Marine and Freshwater Research, 1999)
Mussels (Perna canaliculus) (Gmelin, 1791) collected from mid and low tide rocky platforms along the east coast of the South Island of New Zealand differed in dry weight condition index between shore levels. Mussel condition was c. 15% lower at mid tide level than the low tide level and there was greater variation between shore level than between sites. Feeding experiments were conducted at 15°C with mussels collected from mid and low tide levels using Isochrysis galbana as the food. Clearance rate depended upon body size, shore level, and season. During summer clearance rates of mid and low tide mussels were similar. However in winter, increased filtration rates were recorded in mussels from the mid tide level compared with those from the low tide. In addition, for mussels from both shore levels, winter rates were higher than those recorded in the summer. Nitrogen excretion by mussels also showed seasonal and shore level differences. High values for ammonia excretion of mussels collected from the mid tide during winter suggests they utilise metabolic reserves to maintain their basal metabolism. Although our results suggest that increased filtration rates for mid tide mussels might compensate for reduced feeding time, in the winter, larger mussels from the mid tide level would be unlikely to obtain sufficient energy for maintenance or growth. Large mussels were infrequent in the mid tide population, where the mean length was 62.5 mm compared with 75.1 mm from the low tide. It is concluded that nutrient limitation, as a result of reduced feeding time can act as a significant stress factor limiting the growth potential of mussels settled at the mid tide level.

Further feral poeciliid fish in New Zealand fresh waters, with a key to species - R. M. McDowall (New Zealand Journal of Marine and Freshwater Research, 1999)
The poeciliid fish, Phalloceros caudimaculatus (commonly referred to as the “caudo”), is recorded from the wild for the first time, occurring in stock‐water troughs on a farm near Kamo in Northland, New Zealand. The populations in the stock troughs reputedly came from a nearby stream c. 10 years ago, although a preliminary search has failed to reveal them to be there now. Presence of an additional exotic fish in New Zealand fresh waters is a matter for concern, and requires management. To facilitate recognition off. caudimaculatus , and its distinction from other poeciliids present here, a diagnosis is provided to enable identification, together with notes on natural history, and a key for the identification of the five species of Poeciliidae now known from natural waters in New Zealand.

El Niño and decadal effects on sea‐level variability in northern New Zealand: A wavelet analysis - Derek G. Goring; Robert G. Bell (New Zealand Journal of Marine and Freshwater Research, 1999)
Sea‐level data from two sites in northern New Zealand, along with the Southern Oscillation Index (SOI), are analysed for interannual and decadal variability using wavelets. The analysis shows, using statistically significant wavelet power, there is a significant relationship between mean sea level (MSL) and SOI. However, the relationship is highly variable, both in magnitude and in the range of time‐scales over which it occurs. This non‐stationarity necessitates the use of techniques such as wavelets for analysis. An interdecadal response in MSL around northern New Zealand has been isolated, with shifts occurring in 1950 and the late 1970s. This behaviour in MSL appears to coincide with shifts in the Pacific Decadal Oscillation, thought previously to be largely centred in the North Pacific. A strong correlation between SOI and sea surface temperature (SST) is also demonstrated. This relationship appears to be stable in magnitude (a large change in SOI produces a large change in SST) and to occur over the same range of time‐scales. More SST and MSL data are required for other parts of New Zealand to determine whether these findings apply elsewhere.

Propeller scars on and known home range of two orca (Orcinus orca) in New Zealand waters - Ingrid N. Visser (New Zealand Journal of Marine and Freshwater Research, 1999)
Two orca (Orcinus orca , Linnaeus, 1758), photo‐identified as part of an ongoing study in New Zealand waters, have a series of deep scars in their dorsal lumbar‐caudal regions which suggests they were caused by propellers. One of the animals, first noted to have the scars in 1982, is considerably smaller than an adult of similar age. The known home range of these orca are presented. A third orca hit by a boat is presumed dead.

New and rare tropical and subtropical fishes from northern New Zealand - Malcolm P. Francis; Craig J. Worthington; Peter Saul; Kendall D. Clements (New Zealand Journal of Marine and Freshwater Research, 1999)
Five fish species (Platax teira, Abudefduf vaigiensis, Chromis flavomaculata, Coris dorsomacula , and Aluterus scriptus) are recorded from New Zealand for the first time, and five species (Forcipiger flavissimus, Chromis vanderbilti, Chrysiptera rapanui, Parma kermadecensis , and Thalassoma lutescens) are newly recorded from mainland New Zealand. Five other species that have been reported previously in the popular press, or by name only, are confirmed as members of the New Zealand fauna (Carcharhinus longimanus, Etelis carbunculus, Istiophorus platypterus, Acanthocybium solandri , and Aseraggodes bahamondei) . New observations of 20 previously reported tropical and subtropical species are also presented. Many of the fishes were observed in autumn 1996, 1998, and 1999, indicating recruitment or immigration when sea surface temperature (SST) was higher than average. Major influxes of tropical and subtropical fishes apparently occur during warm summers, although some warm periods were not accompanied by influxes, and a few tropical and subtropical fishes arrived when SST was average or below average. The most likely upstream source of reef fish larvae is Norfolk Island, and the principal transport mechanism is probably the East Auckland Current. The discovery in north‐eastern New Zealand of single individuals of Parma kermadecensis and the yellow form of Chrysiptera rapanui , both previously regarded as Kermadec Islands endemics, provides evidence for occasional larval transport from the Kermadecs to north‐eastern New Zealand.