Population structure and relative abundance of blue cod ( Parapercis colias ) off Banks Peninsula and in Dusky Sound, New Zealand - Michael P. Beentjes; Glen D. Carbines (New Zealand Journal of Marine and Freshwater Research, 2005)
Estimates of blue cod ( Parapercis colias ) relative abundance and population structure were made from potting surveys of Banks Peninsula and Dusky Sound, New Zealand in 2002. Five inshore and two offshore strata around Banks Peninsula, and five strata between the inner fiord and the open coast of Dusky Sound were surveyed. In Banks Peninsula the overall mean catch rate (all fish) was 2.13 kg/pot per h (range 0.04–4.74) and coefficient of variation (CV) was 10.8%. Blue cod from inshore strata were significantly smaller than those from offshore strata, catch rates were lower, and the sex ratio was skewed towards males (inshore 2.2:1, offshore 0.74:1). In Dusky Sound the overall mean catch rate was 2.69 kg/pot per h (range 1.28–8.42), CV was 6.3%, highest catch rates were on the open coast, and overall sex ratio was 0.78:1 (male:female). Blue cod in the 1940s from throughout New Zealand were on average larger than blue cod in Banks Peninsula and Dusky Sound during this survey. Low relative abundance and small size of blue cod from the more accessible inshore areas, is consistent with fishing pressure causing a reduction in size and probably abundance, particularly in Banks Peninsula inshore strata. In Banks Peninsula, sex ratios in inshore areas are skewed towards males, possibly a result of fishing pressure. The results support other studies on protogynous fish species in which the removal of the larger final sex fish (males), promotes sex inversion. The plasticity of the sex inversion means that blue cod may be capable of restoring optimal sex ratios in the natural state, but may over‐compensate with size specific anthropogenic removal of large numbers of individuals that would otherwise inhibit the sex inversion process.

Gymnodinoid genera Karenia and Takayama (Dinophyceae) in New Zealand coastal waters - Miguel F. de Salas; Lesley L. Rhodes; Lincoln A. Mackenzie; Janet E. Adamson (New Zealand Journal of Marine and Freshwater Research, 2005)
New Zealand has been subject to massive blooms of gymnodinoid dinoflagellates over the last decade and in some instances marine biota mortalities. Respiratory problems for people impacted by aerosols from these blooms have occurred. However, because of the difficulty in definitively identifying gymnodinoid dinoflagellates, the identities of the causative organisms have not always been established with certainty. This paper documents the occurrence of several newly described species in the genera Karenia and Takayama in New Zealand's coastal waters as determined by analysis of DNA sequence data. The species include Karenia umbella de Salas, Bolch & Hallegraeff, Takayama helix de Salas, Bolch, Botes & Hallegraeff, and T. tasmanica de Salas, Bolch & Hallegraeff, which are known to have caused fish kills in Tasmanian (Australia) waters in the past. Liquid chromatography‐mass spectrometry analyses of mass cultures of these dinoflagellates have been negative for neurotoxic brevetoxins. The species designation of several unidentified gymnodinoid species (designated Gymnodinium sp.) isolated from New Zealand waters and maintained in the Cawthron Collection of Micro‐algae were also identified on the basis of their DNA sequences.

Effects of forest harvesting and woody debris removal on two Northland streams, New Zealand - Brenda R. Baillie; Kevin J. Collier; John Nagels (New Zealand Journal of Marine and Freshwater Research, 2005)
The short‐term effects of Pinus radiata forest harvesting to the stream edge followed by stream‐cleaning (removal of woody debris from the stream channel), on instream light levels, stream temperature, dissolved oxygen concentrations, and aquatic invertebrates were assessed in streams draining partly (25% clear‐cut) and totally (100% clear‐cut) harvested catchments, compared with nearby indigenous forest and mature pine plantation reference sites. There were marked increases in in‐stream light levels and water temperatures following forest harvest and stream‐cleaning at both sites. In‐stream light levels increased from 8–13% to 60–90% and maximum monthly water temperatures increased on average by 5.6°C in the partly harvested and 3.6°C in the fully harvested catchment. Dissolved oxygen levels decreased at both sites shortly after harvest (94%‐71% saturation in the partly harvested catchment; 72%‐37% saturation in the totally harvested catchment), increasing to 75% and 81%, respectively, 1 year later. Although aquatic invertebrate mean density and taxa richness increased at both sites following harvest, the relative abundance of sensitive mayfly, caddisfly, and stonefly species decreased and community composition changed to one dominated by Chironomidae (midges) or Mollusca. Impacts relative to pre‐harvest conditions were not as marked in the totally harvested catchment, possibly because of pre‐existing elevated stream temperatures and high levels of sand and silt. Any downstream protection provided by the forested headwaters of the partly harvested catchment was soon lost after the stream entered the clear‐cut area, although these forested headwaters may provide a potential source of aquatic invertebrates for re‐colonisation in the future as water quality and habitat recover. Our results suggest that: (1) pre‐existing constraints on habitat quality can influence the magnitude of harvesting impacts; and (2) length of stream edge harvested may be a better indicator of impact on some aspects of stream ecology, such as lighting, stream temperature, dissolved oxygen, and aquatic invertebrate community composition, than percentage of catchment harvested. This study also highlights the importance of considering the hydro‐logical and landscape context for mitigating harvesting and wood management impacts on stream ecosystems.

Towards a revision of Candoninae (Crustacea: Ostracoda): Australian representatives of the subfamily, with descriptions of three new genera and seven new species - Ivana Karanovic (New Zealand Journal of Marine and Freshwater Research, 2005)
The following new Candoninae taxa are described: Neocandona novitas n. gen., n. sp.; N. newmani n. gen., n. sp.; Origocandona inanitas n. gen., n. sp.; O. gratia n. gen., n. sp.; Areacandona mulgae n. gen., n. sp.; A. arteria n. gen., n. sp; and Humphreyscandona imperfecta n. sp. Together with these seven species the Australian Candoninae fauna now includes 27 living representatives classified into 10 different genera. Seven genera (three new and four previously described) belong to the same phylogenetic line and are included into the tribe Humphreyscandonini n. trib., described in the present paper. The most prominent characteristic of this tribe is a well chitinised, sharply pointed part of the lobe “b” on the hemipenis projected dorsally. The rest of the Australian genera belong to three separate groups, two of them being in the tribes Candonini and Namibcypridini, whereas the third is not yet defined. This paper contains discussion on the phylogenetic relationships of the Australian Candoninae and keys to all the Candoninae genera and species known from this continent. Also, scanning electron microscope (SEM) photographs of the carapaces of the majority of them are provided. All the new species are from subterranean waters of the Pilbara Region in Western Australia.

Movement of male Heterozius rotundifrons (Crustacea: Decapoda: Brachyura) depends upon local sex ratio - B. A. Hazlett; C. E. Bach; G. A. Thompson; C. L. McLay (New Zealand Journal of Marine and Freshwater Research, 2005)
Heterozius rotundifrons is a New Zealand endemic crab that lives in the intertidal zone and is found under rocks during low tides. We investigated the role of the local sex ratio (= under rock) in affecting movement patterns of this crab. In the laboratory, male crabs moved more when the sex ratio was male biased. Field surveys suggested that there is an upper limit to the number of males found under rocks, even as the number of females increases. Field manipulations demonstrated that when the sex ratio under a rock is female biased there is no effect on female movement but when the ratio is male biased, males move away more frequently and move further. This increased movement by males is probably related to avoidance of male‐male competition for females.

Sedimentary record of radiolarian biogeography, offshore eastern New Zealand - C. J. Hollis; H. L. Neil (New Zealand Journal of Marine and Freshwater Research, 2005)
Examination of 38 surface sediment samples from offshore eastern New Zealand, between 33°S and 54°S, yielded 100 radiolarian taxa, which are common to abundant in sediments deposited at > 1000 m water depth but rare at shallower depths. In general, radiolarians are most abundant, most diverse, and best preserved in assemblages north of the Subtropical Front (STF). Multivariate analysis of census data for 29 radiolarian‐rich samples identifies six sample groups and eight species groups. The STF forms a major biogeographic barrier, separating three transitional zone (TR) and three subantarctic zone (SA) sample groups. The three primary sample groups (TR1, TR2, SA1) record a southward latitudinal trend of decreasing abundance of subtropical‐tropical or warm‐water taxa (species group 4) and increasing abundance of subantarctic ‐Antarctic or cool‐water taxa (species groups 7 and 8). Two secondary sample groups (TR3 and SA2) may record the influence of shallow‐water processes or strong surface currents on either side of the STF. A distinctive sample group (SA3), characterised by low abundance and diversity, records relatively shallow, stratified, and silica‐limited conditions of the central Campbell Plateau.

Coastal circulation within the Banks Peninsula region, New Zealand - Janelle V. Reynolds‐Fleming; Jason G. Fleming (New Zealand Journal of Marine and Freshwater Research, 2005)
The transport of nutrients, larvae, and sediment around coastal headlands critically depends on the balance of forces that direct the currents very near to the shore. The Banks Peninsula region, New Zealand, was selected to study nearshore circulation around coastal headlands. The relative influences of tides and wind on the current were determined using an acoustic Doppler current profiler (ADCP) deployed 2 km offshore in Pegasus Bay. Results indicated that the M 2 tide is the dominant tide and explains 30% of the variance. Low frequency variability was strongly correlated with wind in the offshore direction and explained a further 20–40% of the variability. Finally, mean residual flows were 2 cm/s southward along shore, which supports the hypothesis that an eddy is episodically present in Pegasus Bay. This study is the first to quantitatively document the nearshore circulation in the Banks Peninsula region.

Foraminiferal record of sewage outfall impacts on the inner Manukau Harbour, Auckland, New Zealand - Andrew Matthews; Hugh R. Grenfell; Bruce W. Hayward; Mark Horrocks (New Zealand Journal of Marine and Freshwater Research, 2005)
The fossil foraminiferal faunas preserved in intertidal sediment in six cores document the impact of human activities on the ecosystems of the north‐east arm of the Manukau Harbour, Auckland, New Zealand. They indicate that Polynesian forest clearance and horticulture had negligible impact on the harbour biota. Before 1960, organic‐rich discharges from four large meat works around the head of Mangere Inlet produced changes in nearby foraminiferal faunas but did not affect faunas in the more seaward part of the arm. Initial early European increases in organic nutrients from the meat works resulted in the development of weak hypertrophic zones around the outfalls, characterised by higher absolute abundances of benthic foraminifera and ostracods and possible benthic algal blooms. Higher organic nutrient levels in one core closer to an outfall produced eutrophic and anoxic conditions with no foraminifera (abiotic zone). In 1960 the Mangere Sewage Treatment Plant (MSTP) was opened and the meat works and other outfalls progressively closed. This change coincided with a sharp increase in zinc (Zn) and lead (Pb) levels in sediments throughout the arm, attributed to a rapid increase in motor vehicle numbers and stormwater run‐off. The MSTP discharged vast quantities of nutrient‐ and mud‐rich fresh water into the seaward part of the arm, resulting in an order of magnitude increase in sedimentation rates throughout most of the arm and a widespread change in the foraminiferal faunas. Foraminiferal abundance generally decreased and species diversity increased with the appearance of numerous juvenile foraminiferal shells carried in by the incoming tide from subtidal habitats nearer the harbour mouth. Also appearing in large numbers in the post‐1960 sediment are planktic foraminifera, large diatom valves, and sponge sterrasters, all of which are inferred to have been transported in. The sudden increase in displaced microfossils may be a result of a combination of fresh water‐induced flocculation and increased “stickiness” of the substrate from the growth of benthic algal mats, resulting from the high nutrient output from the MSTP.

Mean and variability in the Wairarapa and Hikurangi Eddies, New Zealand - Stephen M. Chiswell (New Zealand Journal of Marine and Freshwater Research, 2005)
The mean and variability of the circulation off the east coast of the North Island, New Zealand are investigated using shipboard conductivity‐temperature‐depth (CTD) and satellite altimeter data collected between 1993 and 2003. The altimeter data are used to adjust the in situ observations for the mesoscale eddy variability before computing the 11‐year mean in dynamic height. Mean dynamic height shows two anticyclonic eddies, centred near 178.3°E, 41.2°S and 176.2°E, 42.4°S. These locations are consistent with previous historical observations of the Wairarapa and Hikurangi Eddies, respectively. A long‐term trend in both in situ and satellite data shows that dynamic height rose at an average rate of up to 2 dyn cm year ‐1 in the centre of the Wairarapa Eddy which is consistent with a strengthening of the eddy over the 11 years. The satellite data show periodic shedding of the Wairarapa Eddy from near East Cape at a rate of between two and three eddies per year. Thus, rather than indicating a permanent stationary eddy, the mean eddy reflects a region where the eddies tend to stall out or merge with the previous eddy. Often, the eddies will continue up the Hikurangi Trough so that the Hikurangi Eddy can be regarded as an older Wairarapa Eddy.

First record of mosquitofish, Gambusia holbrooki , in Tasmania, Australia: Stock structure and reproductive biology - John P. Keane; Francisco J. Neira (New Zealand Journal of Marine and Freshwater Research, 2004)
The first population of mosquitofish, Gambusia holbrooki , was discovered in a wetland area of the upper Tamar Estuary, northern Tasmania, Australia, in November 2000. We report aspects of the structure and reproductive biology of this population, based on 1567 fish collected between August 2001 and January 2002. Females dominated most catches. Maximum lengths were 48.9 and 23.6 mm standard length (SL) for females and males, respectively. Growth of the over‐wintered cohort was evident from October, when temperatures reached >19°C; growth rates in the young‐of‐season cohort from length frequency plots were 0.38 mm/ day for females and 0.19 mm/day for males. Estimated SL at 50% maturity for females (25.0 mm) and males (17.4 mm) were attained within 7 weeks of birth. Developing embryos were present from mid October and offspring from mid November; average number of stage III embryos was 55.5 (3–144). Given their rapid reproductive turnover (c. 34‐day gestation period) and resilience to broad environmental conditions, it is likely that this exotic pest will spread to other Tasmanian localities, as it has already been discovered in areas near the wetlands since the completion of this study.

Impacts of riparian afforestation on stream biofilms: An exotic forest‐native grassland comparison - Ross M. Thompson; Colin R. Townsend (New Zealand Journal of Marine and Freshwater Research, 2004)
The nature of benthic biofilm was assessed in four streams in New Zealand, two flowing through native tussock grassland and two through exotic Pinus radiata forest. Components of the biofilm were described using epi‐fluorescent staining (DAPI) and scanning electron microscopy (SEM) of rock and wood substrata. DAPI and SEM analyses showed significantly more bacteria and fungi on rock and wood in tussock as opposed to pine streams. This emphasises the importance of the heterotrophic community even in systems which have abundant light available for primary production. The lack of a significant heterotrophic biofilm in pine streams was unexpected, and we speculate that chemical characteristics of the water may be responsible.

Letters to the editor - M. J. Unwin; M. J. Uddstrom; David S. Kirby (New Zealand Journal of Marine and Freshwater Research, 2004)
Re: Kirby, D. S.; Abraham, E. R.; Uddstrom, M. J.; Dean, H. 2003: Tuna schools/aggregations in surface longline data 1993–98. New Zealand Journal of Marine and Freshwater Research 37 : 633–644.

Quantitation of metallothionein mRNA from the New Zealand common bully ( Gobiomorphus cotidianus ) and its implications for biomonitoring - Andrew D. Laurie (New Zealand Journal of Marine and Freshwater Research, 2004)
Metallothionein (MT) is a protein found in most eukaryotes where its primary role is the regulation of homeostasis of the essential metals copper and zinc. MTs have an additional protective role through their binding of toxic metals such as cadmium and mercury. Increased expression of MT in response to harmful levels of these metals has been demonstrated for several aquatic species. In this study, the expression of MT in the liver tissue of the New Zealand common bully Gobiomorphus cotidianus was measured by quantifying MT mRNA. A statistically significant increase in MT expression was observed in fish exposed to copper for 48 h, but not those exposed to zinc. Field sampling of common bullies showed a wide variation in individual hepatic MT mRNA levels which did not correlate with fish age, sex, or sampling location. A comparison of two populations of common bullies from a polluted and a control site showed a two‐fold higher mean MT mRNA level in fish from the polluted site. Implications for using MT expression in the common bully as a bio‐monitoring tool are discussed.

Atypical size selection of captive school prawns, Metapenaeus macleayi , by three recreational fishing gears in south‐eastern Australia - Matt K. Broadhurst; Russell B. Millar; Damian J. Young; Michael E. L. Wooden; Stuart Rowland (New Zealand Journal of Marine and Freshwater Research, 2004)
Three manipulative experiments were done to estimate the selectivity of conventional and new sizes and configurations of mesh for school prawns, Metapenaeus macleayi , in three south‐eastern Australian recreational fishing gears (haul, push, and scoop nets). The treatment meshes examined were: (1) conventional‐sized, diamond‐shaped mesh used in all gears (20 mm in scoop nets and 30 mm in push and haul nets); (2) 30 mm in scoop nets; and (3) 40‐mm diamond‐ and (4) 23‐mm square‐shaped mesh in all gears. In all experiments, known quantities of school prawns (6–24 mm carapace length (CL)) were placed in purpose‐built enclosures, monitored to ensure no experimental‐induced stress (as measured by changes in L‐lactate in their haemolymph) and the replicate treatments of the various gear configurations deployed. Escapees from the various treatment nets were collected from the enclosures using fine‐meshed nets. Logistic selection curves were derived for all treatment nets and specific comparisons made within and among gears. All nets had 50% retention lengths (L 50 ) comparable to other penaeid‐catching gears with similar mesh sizes, but most had selection ranges (SRs) that were atypically inflated. The large SRs were attributed to a combination of factors that included the mesh geometry and towing speed of the gears and the behaviour of school prawns. The 20‐mm scoop net had the smallest selection parameters, retaining >99% of individuals larger than 13 mm CL. Mesh size in this gear would need to be increased to at least 30 mm to allow some maturing prawns (>18 mm CL) to escape.

Variation in sunscreen compounds (mycosporine‐like amino acids) for marine species along a gradient of ultraviolet radiation transmission within doubtful sound, New Zealand - Miles D. Lamare; Michael P. Lesser; Mike F. Barker; Thomas M. Barry; Kate B. Schimanski (New Zealand Journal of Marine and Freshwater Research, 2004)
We examined the response of four species of New Zealand marine algae ( Ecklonia radiata, Apophlaea lyallii, Rhodymenia spp., Ulva lactuca ) and a sea urchin ( Evechinus chloroticus ) to spatial variation in ultraviolet radiation (UV‐R) by examining the concentration of UV‐R absorbing compounds known as mycosporine‐like amino acids (MAAs). The purpose was to understand how, and the degree to which, local marine species could potentially respond to any future increases in incident UV‐R in the New Zealand marine environment. The research was undertaken in Doubtful Sound, where we observed a gradient of water column UV‐R transmission along the 40 km length of the fiord. We examined spatial differences in MAAs along the UV‐B gradient in the macrophytes and temporal changes in MAAs in sea urchin gonads. Among the algae, thallus MAA concentrations (nmol mg –1 protein) ranged from 12.5 to 87.8 in E. radiata , from 433.1 to 1446.4 in A. lyallii , 12.7 to 103.4 in Rhodymenia spp., but were not detected in U. lactuca . For E. chloroticus , gonadal MAA concentrations ranged from 83.9 to 224.3 nmol mg –1 protein spatially, and over the year from 1.85 to 14.12 nmol mg –1 dry weight (DW) depending on site and gametogenic cycle. Laboratory manipulations indicated that concentrations of MAAs in E. chloroticus gonads and eggs are influenced by diet. MAA concentration could be correlated with UV‐B intensities in two of the algal species. E. chloroticus MAA concentrations could also be correlated with UV‐B transmission, which we concluded was a reflection of the greater ingestion and accumulation of MAA‐rich macrophytes at those sites where higher ambient UV‐R induced greater MAA concentrations to occur in the algae. Given this, we suggest that one response of marine species to increases in UV‐B would be an increase in the synthesis and/or accumulation of MAAs for photoautotrophs and a dietary accumulation of those MAAs in E. chloroticus , an important herbivore in this system.

Crustorhabditis chitwoodi sp. nov. (Nematoda: Rhabditidae): An intertidal species from the coast of New South Wales, Australia, with observations on its ecology and life history - Warwick L. Nicholas (New Zealand Journal of Marine and Freshwater Research, 2004)
A new species, Crustorhabditis chitwoodi , was discovered in nutrient agar plates inoculated with beach sand collected from an ocean beach in New South Wales, Australia. The three other known species of the genus have all been found as commensal inhabitants of ocypodid shore crabs. It is suggested that the sand inoculum was seeded with dauer larvae of the nematode that had been dispersed by scavenging crabs. The new species is distinguished from the three previously described species by possessing a smaller number of differently arranged bursal papillae, eight rather than 10. The species is amphimictic, oviparous, and produces abundant dauer larvae in culture, which can be sustained indefinitely on sea water nutrient agar in which it feeds on associated bacteria.

Melanistic southern right‐whale dolphins ( Lissodelphis peronii ) off Kaikoura, New Zealand, with records of other anomalously all‐black cetaceans - Ingrid N. Visser; Dagmar Fertl; L. Todd Pusser (New Zealand Journal of Marine and Freshwater Research, 2004)
Reports of anomalously pigmented cetaceans, including melanistic (all‐black) individuals are infrequent. We observed four melanistic southern right‐whale dolphins ( Lissodelphis peronii ) including a calf, off Kaikoura (42°34'S, 173°50'E), New Zealand. We also compiled records of melanistic individuals from five other species of cetaceans. The ecological context of melanistic pigmentation of cetaceans is not well understood; however, it may increase heat absorption, affect ability to capture prey, impair visual/social communication, and/or increase conspicuousness to predators.

Growth and survival of early juvenile trumulco snail Chorus giganteus (Gastropoda: Muricidae) fed two prey species - C. S. Gallardo; M. A. Diaz; C. Varela (New Zealand Journal of Marine and Freshwater Research, 2004)
Comparative data were obtained on the growth and survival of early juveniles of the trumulco snail Chorus giganteus from settlement to an age of 4 months when fed either of the mussel species Semimytilus algosus or Perumytilus purpuratus . Growth of the snails after 4 months was significantly greater when fed S. algosus , ending with a mean size of 6162 μm compared with 5192 μm with P. purpuratus . Survival between the two fed groups was not prey‐specific. Survival of the unfed control group was significantly lower beginning at 14 days post‐metamorphosis. After 63 days, survival within the fed groups was 63.2% and only 16.5% in the unfed control group. The similarity of growth and survival of these juveniles during the first 2 months in culture suggested that both prey species had the same food value. The energy cost to the snails of penetrating the different prey species diverged after the second month, as the shells of P. purpuratus became thicker and thus more difficult to penetrate than those of S. algosus . This was reflected as differences in growth rates for snails fed the 2 species in the following 2 months of the experiment. Unfed snails grew by 107 μm in average during the first 2 weeks of the experiment and then ceased demonstrating the importance of nutritional reserves carried by the larva from hatching through early benthic survival.

Thermal structure and energy budget in a small high mountain lake: La Caldera, Sierra Nevada, Spain - Miguel Rodríguez‐Rodríguez; Enrique Moreno‐Ostos; Inmaculada De Vicente; Luis Cruz‐Pizarro; Sergio Luiz Rodrigues Da Silva (New Zealand Journal of Marine and Freshwater Research, 2004)
This work examines the diel change of energy storage and its associated patterns of thermal stratification during the ice‐free period in a high mountain lake (La Caldera Lake, Sierra Nevada, Spain), in response to meteorological conditions. Bihourly data have been implemented to a standard methodology of surface heat exchange calculations in lakes. Strong variations have been observed on the diverse components of the energy budget at different time scales, ranging from diel to seasonal. Additionally, time‐series analyses have been applied to reveal the underlying periodicities involved in relation to the different variables studied. The results obtained from this study provided realistic conditions for the environmental modelling of such processes, which are very sensitive in time scale.

Feeding ecology of whelks on an intertidal sand flat in north‐eastern New Zealand - M. J. Stewart; R. G. Creese (New Zealand Journal of Marine and Freshwater Research, 2004)
The dispersion patterns and feeding behaviour of intertidal whelks were investigated in north‐eastern New Zealand. Aggregations of whelks feeding on clams occurred regularly, with an average of 15–20 individuals per aggregation. Death of clams was attributable to predation in up to 50% of the aggregations, although scavenging of dead and moribund animals was the main activity of whelks. Laboratory and field studies showed that Lepsiella scobina (generally not considered a soft shore species) was the main whelk predator at Lews Bay, Whangateau Harbour, drilling a small neat hole through the clam shell. The distinction between Cominella spp. as predators or scavengers is not so clear. Reseeding of intertidal clams, Austrovenus stutchburyi , has been proposed as a technique for reestablishing populations in some degraded New Zealand estuaries. The impact of whelk predation has many implications for A . stutchburyi reseeding. Both L. scobina and Cominella adspersa may potentially prey on newly reseeded clams as they preferentially attacked small clams in the laboratory. On‐growing to a larger size before reseeding may be advantageous although large size was not found to protect prey from predation. Additionally, no seasonal trend in whelk activity was found.

Relationship between long‐term changes in algal community structure and herbivore diet at the Three Kings Islands, New Zealand - W. Lindsey Zemke‐White; Kendall D. Clements (New Zealand Journal of Marine and Freshwater Research, 2004)
We examined temporal changes at the Three Kings Islands, New Zealand in 1993 and 2002 in the diet of the endemic herbivorous fish Odax cyanoallix (Family Labridae) and in habitat‐forming macroalgae, and compared these with published accounts from 1979. The diet of O. cyanoallix predominantly comprised the laminarian Ecklonia radiata in 1993, and the fucoids Sargassum johnsonii and Landsburgia quercifolia in 2002. In depths S. johnsonii was dominant in 1979 and 2002 and absent in 1993. E. radiata was absent in 1979, abundant in 1993, and rare in 2002. A period of significantly lower sea‐surface temperatures (SST) at the Three Kings Islands in 1990–95 corresponded to an unusually long El Niño event. The low SST may have resulted in the failure of S. johnsonii to grow and/or recruit during the El Niño event, leading to the observed changes. This study demonstrates variability in fucoid and laminarian assemblages over large time scales that are reflected in diet shifts in a species of herbivorous fish.

Temperature effects on the embryo development and hatching of the spiny lobster Sagmariasus verreauxi - Graeme A. Moss; Philip J. James; Sarah E. Allen; Michael P. Bruce (New Zealand Journal of Marine and Freshwater Research, 2004)
Factors affecting the development of the embryos and production of larvae of the spiny lobster Sagmariasus verreauxi were investigated. Mature lobsters were collected from the fishery in New Zealand and held in captivity until they moulted, mated, and extruded eggs. For females, moulting took place in winter (July/August) and mating occurred 58–88 days later in early spring. The ovigerous females were then held at three temperatures and embryo development monitored at approximately weekly intervals. Mean times to hatch were 55, 75, and 130 days at 20°C, 17°C, and 13°C respectively. The total number of larvae that hatched from each female ranged from 0.97 to 1.4 million. The theoretical temperature at which embryo development ceases (a biological zero) for S. verreauxi , of 9.4°C, was calculated from data on the appearance of the median eye, the eyes and the chromatophores, and the time to hatch. An eye index formula was also derived to allow prediction of time to hatch at a range of temperatures using the cumulative difference between the rearing temperature and the biological zero. First instar phyllosomas from embryos reared at 20°C were significantly smaller than those from 17°C and 13°C but there was no significant difference in fitness. This study shows that hatching can be spread over a number of months, without significantly affecting larval quality, simply by manipulating holding temperature.

Contribution of photosynthetic gains during tidal emersion to production of Zostera capricorni in a North Island, New Zealand estuary - Anne‐Maree Schwarz (New Zealand Journal of Marine and Freshwater Research, 2004)
Photosynthetic characteristics of intertidal Zostera capricorni were measured under different tidal conditions in Whangapoua Harbour on the eastern Coromandel Peninsula, New Zealand, and compared with permanently submerged seagrass beds. Photosynthetic characteristics were measured using pulse amplitude modulated (PAM) fluorom‐etry and oxygen (O2) electrode techniques. Gross light saturated photosynthesis measured as oxygen exchange averaged 5.74 and 5.36 mg O 2 g –1 dry weight (DW) h –1 and leaf respiration rates averaged 1.22 and 1.38 mg O 2 g –1 DW h –1 , for intertidal and subtidal plants respectively. Photosynthesis of both intertidal and shallow subtidal plants was light saturated at between 195 and 242 μmol photons m – 2 s –1 , suggestive of acclimation to a high light environment. Despite the period of exposure at low tide clearly being an important time for photosynthetic gains for intertidal plants, when water clarity was sufficiently high, maximum rates of photosynthesis were also possible when the beds were submerged. If average water clarity was at the clearer end of a range measured for this site ( K d = 0.85 m –1 ) then it was calculated that for intertidal seagrass beds growing at mean sea level in Whangapoua, c. 50% of above‐ground production could occur while plants were submerged.

Impact of land use on the faecal microbial quality of hill‐country streams - A. Donnison; C. Ross; B. Thorrold (New Zealand Journal of Marine and Freshwater Research, 2004)
Faecal contamination of rural streams is of increasing concern in New Zealand. This study assessed hill‐country streams in the Whatawhata district that were impacted by pastoral farming, indigenous forest, or Pinus radiata forest; by measuring Escherichia coli bacteria at 14 sampling sites fortnightly for 2 years. E. coli concentrations were highest in streams flowing through grazed pasture. In both years there was a noticeable seasonal pattern in all streams irrespective of land use, with highest bacterial concentrations in summer and autumn and lowest in winter and early spring. There was no obvious correlation between E. coli concentration and rainfall or stream flow. In those streams impacted by a change in land use from pastoral to pines during the study, E. coli concentration fell rapidly and remained at levels lower than those in streams impacted by either indigenous or 7‐year pine forests. As E. coli was detected in all but two samples, the water in these streams is not suitable for human consumption. The pastoral streams consistently failed to meet stock drinking‐water guidelines (median concentration not greater than 100 E. coli 100 ml –1 ) and the forest streams failed to do so in summer. Twenty‐eight percent of pastoral samples, 25% of indigenous forest samples, 14% of 7‐year pine forest samples, and 5% in New Pines stream samples (after planting) had E. coli concentrations associated with a high level of risk for contact recreation (>500 E. coli 100 ml ‐1 ) and the high concentrations usually occurred in summer.

Anguillicolosis in the short‐finned eel Anguilla australis : Epidemiology and pathogenicity - François Lefebvre; Tobias Schuster; Marcel Münderle; Mike Hine; Robert Poulin (New Zealand Journal of Marine and Freshwater Research, 2004)
A sample of 189 short‐finned eels ( Anguilla australis ) from four geographical areas in New Zealand were examined for the occurrence of the swimbladder nematode Anguillicola spp. Anguillicola novaezelandiae was found in three of the four localities. Overall, the prevalence was low ( Anguilla anguilla‐Anguillicola crassus ), it was concluded that the New Zealand short‐finned eels do not greatly suffer from this infection. In particular, no effect of infection on body condition was detected. The damage caused by the parasite to the swimbladder was minimal, even in large silver eels about to undertake a long journey at great depth to reach their spawning grounds in the Pacific. A review of the available literature is presented to update the current knowledge of the distribution of Anguillicola infections in New Zealand.

Validation of qualitative habitat descriptors commonly used to classify subtidal reef assemblages in north‐eastern New Zealand - N. T. Shears; R. C. Babcock; C. A. J. Duffy; J. W. Walker (New Zealand Journal of Marine and Freshwater Research, 2004)
On shallow temperate subtidal reefs, habitat types are usually defined subjectively by the dominance or presence of major macroalgal species. Many of these habitat types (e.g., urchin barrens, kelp forest) are frequently used in the literature but little attempt has been made to quantitatively define these habitats. A survey of shallow subtidal reefs in north‐eastern New Zealand identified a number of commonly occurring “habitat types”. In this paper the abundances of habitat‐forming species within each of these habitats are quantified and the validity of the subjective classification system is tested. In addition to previously‐described reef habitats from north‐eastern New Zealand a number of other habitat types were encountered and described in this study (e.g., “mixed algae”, “red foliose algae”, and “Caulerpa mats”). The algal communities within each habitat were biologically distinct and there was strong concordance between the grouping of samples from cluster analysis and the subjective habitat type assigned to each. The habitat classification system was reliable and canonical analysis of principal coordinates revealed an overall classification success of 81%. This provides strong evidence that the habitat classifications used in this study are biologically meaningful based on the abundances of habitat‐forming algal groups. Furthermore, this demonstrates that these habitat types can be reliably categorised visually, which has important applications in classification and mapping of the marine environment.

Water column stratification and the spatial and temporal distribution of phytoplankton biomass in Tasman Bay, New Zealand: Implications for aquaculture - Lincoln MacKenzie; Janet Adamson (New Zealand Journal of Marine and Freshwater Research, 2004)
Temporal changes in the abundance and horizontal and vertical distribution of phytoplankton biomass (chlorophyll a) in Tasman Bay, New Zealand were associated with changes in water column stratification, because of seasonal climatic effects and variations in the magnitude of freshwater inflows. The water column throughout the bay was usually strongly stratified. Vertical gradients in salinity, the result of outwelling river plumes overlying deeper more saline waters, usually played the major role in stabilising the water column. However, during summer low river‐flow periods, temperature stratification was also important. A persistent east to west gradient in Simpson's potential energy anomaly (an index of the strength of stratification) existed across the bay at most times, because of the dominant influence of the Motueka River plume. From late spring to late summer most of the nutrient depleted euphotic zone contained low chlorophyll a (Chl. a) concentrations while below the base of the pycnocline, turbid water containing re‐suspended sediments and relatively high Chl. a levels persisted. It is debatable, given the susceptibility of scallops to high levels of suspended silt, whether this condition is beneficial to these commercially important bivalves. Diatom blooms in autumn and spring, representing the annual productivity maxima, occurred when the water column beyond the extent of the Motueka River plume became well mixed. At this time the conditions for shellfish nutrition are probably at their best. At most other times flagellate‐dominated phytoplankton communities within subsurface concentrated Chl. a layers were associated with a mid water column (10–15 m), bay‐wide, pycnocline. This is a common feature of the structure of the water column of Tasman Bay that coincides with the depth range within which scallop growth and survival is highest and mussel nutrition and spat catching is probably optimal. Aquaculture management options and strategies for fisheries enhancement may be developed using these data such as the timing and depth of installation of bivalve spat catching gear to optimise shellfish nutrition and successful spat falls. The future lies in the installation of real‐time monitoring equipment within the bay and development of adaptive phytoplankton productivity models based on hydrodynamic models of water column circulation and vertical structure.

CD‐ROM review - Keith Probert; Brian Paavo (New Zealand Journal of Marine and Freshwater Research, 2004)

Two new species of Xanthocalanus and the first record of Brachycalanus (Copepoda: Calanoida: Phaennidae) from the upper slope, north‐eastern New Zealand - Janet M. Bradford‐Grieve (New Zealand Journal of Marine and Freshwater Research, 2004)
Two new species of Xanthocalanus are reported from the New Zealand continental slope. The female and male of X. longispinus n. sp. is described as well as the female of X. stewarti n. sp. Aspects of X. fallax and X. minor from Norway are re‐described and illustrated where observations differed from previous descriptions. Females of the two new species are distinguished from all other Xanthocalanus by a combination of characteristics of the female leg 5. The terminal segment has 4 spines and the inner terminal spine is completely fused to its segment in both species but is straight in X. longispinus and bent outwards in X. stewarti . The inner lateral spine extends beyond the base of the outer terminal articulated spine in X . longispinus and as far as the base of the outer terminal articulated spine in X. stewarti . The coxal inner border spinules are large, stout and cover a wide area in X. longispinus and are small, pointed and cover a narrow area in X. stewarti . The male may be distinguished from other known males with a styliform right leg 5 because leg 5 does not extend beyond the caudal rami, there are a series of about 8 stiff spines, graded in size, on the distal border of the left exopod segment 2, and the antennule has ancestral segments X‐XV, XVI‐XVII fused on both sides as well as XXII‐XXIII on the right side. Brachycalanus is recorded for the first time from New Zealand waters, although the single, damaged, female specimen is illustrated but not named.

River inputs, re‐mineralisation and the spatial and temporal distribution of inorganic nutrients in Tasman Bay, New Zealand - Lincoln Mackenzie (New Zealand Journal of Marine and Freshwater Research, 2004)
To improve understanding of the temporal and spatial variability of biological productivity relevant to fisheries enhancement within Tasman Bay, New Zealand, it is necessary to evaluate the importance of variations in river inflows on inorganic nutrient dynamics. To achieve this, a series of synoptic surveys of surface and water column salinity fields and inorganic nutrient concentrations were carried out over a 1‐year period, at seasonally representative times, during, and soon after, a range of flow regimes in the major freshwater tributaries of Tasman Bay. An assessment was made of the relative importance of external (i.e., river borne) and internal (i.e., recycling) nutrient sources that control the fertility of the Tasman Bay water column. Flood events in the bay's catchment cause significant changes in the levels of dissolved nitrogen, phosphorus, and silica in surface waters, and on an annual basis 60–70% of the input of “new” dissolved inorganic nitrogen from freshwater tributaries is contributed by the Motueka River. As a consequence there is a pronounced east to west gradient in nutrient enrichment, and oceanic water most frequently intrudes along the eastern shore. Surface salinity and inorganic nutrient distribution patterns and inferred water movements are consistent with the left hand deflection of buoyant river plumes. The predictable timing and magnitude of the winter nitrate/nitrite maxima suggests that light is the main factor limiting phytoplankton production and nutrient assimilation during the winter, and that benthic and pelagic re‐mineralisation processes are the dominant mechanism generating the annual nutrient maxima within the water column as a whole. Calculations suggest that the net accumulation of inorganic nitrogen via endogenous re‐mineralisation over the autumn‐winter period is of a similar order of magnitude to the annual introduction of new nitrogen from freshwater sources. How this compares to inputs of new nitrogen by advection from oceanic sources has yet to be determined.

Descriptions of larvae of Merluccius australis, Macruronus magellanicus , and observations on a larva of Micromesistius australis from southern Chile (Pisces: Gadiformes) - Fernando Balbontin; Flor Uribe; Rolando Bernal; Mauricio Braun (New Zealand Journal of Marine and Freshwater Research, 2004)
Larvae of two commercially important fish species, namely southern hake ( Merluccius australis ) and hoki ( Macruronus magellanicus ), are described for the first time from material collected in southern Chile. Observations on a third species, blue whiting ( Micromesistius australis ), are also provided. The three species demonstrate larval characteristics typical of gadiform fishes, including a short gut, and pigmentation distributed in blotches and bands. Characteristics of the larvae of M. australis from Chile are similar to those observed in sketches from New Zealand, such that the descriptions may be used to identify the larvae from other regions. The similarity of characteristics between M. magellanicus larvae from Chile and Argentina and larvae of M. novaezelandiae from Tasmanian and New Zealand waters demonstrate the taxonomic affinity between these species. The presence of three dorsal fins in a late postflexion Micromesistius australis larva allowed it to be easily recognised.

Water quality impact of a dairy cow herd crossing a stream - Rob J. Davies‐Colley; John W. Nagels; Rob A. Smith; Roger G. Young; Chris J. Phillips (New Zealand Journal of Marine and Freshwater Research, 2004)
The water quality impact of a herd of 246 dairy cows crossing a stream ford was documented. Two cow crossings produced plumes of turbid water associated with very high concentrations of faecal indicator bacteria ( Escherichia coli ) and high suspended solids (SS) and total nitrogen (TN). On the first crossing, towards the milking shed, the cows were tightly‐bunched and produced a sharp spike of contamination ( E. coli peaking at 50 000 cfu/100 ml). After milking, the cows wandered back across the stream as individuals or small groups, and contaminants were less elevated, albeit for a longer period. Light attenuation, measured continuously by beam transmissometer, correlated closely with E. coli , SS, and TN, permitting the total yield of these contaminants to be estimated. Contaminant yields for the two crossings were very similar, suggesting that time taken and whether or not cows are herded may not greatly influence water quality impact. The cows defecated c. 50 times more per metre of stream crossing than elsewhere on the raceway. This study has shown that cattle accessing stream channels can cause appreciable direct water contamination, suggesting that excluding cattle from streams will have major water quality benefits.

First records of the Australian blenny, Omobranchus anolius , from New Zealand - Malcolm P. Francis; Peter J. Smith; Cameron Walsh; Martin F. Gomon (New Zealand Journal of Marine and Freshwater Research, 2004)
Twenty‐four blennies collected in east Auckland, New Zealand, were identified as the Australian oyster blenny, Omobranchus anolius using taxonomic and molecular characters. This species appears to have been introduced recently to New Zealand. Auckland oyster blennies mainly inhabited dead oyster shells in water pooled under intertidal boulders on mudflats. Specimens ranged from small juveniles to large mature males, suggesting that the species is breeding in New Zealand, or that there have been multiple incursion events. Oyster blennies may be capable of colonising estuaries throughout the northern North Island, and possibly farther south. Control or eradication of O. anolius would be facilitated by its intertidal habitat, lack of an escape response when found, and the very limited movement and natural dispersal of adults and larvae.

Land‐use influences on New Zealand stream communities: Effects on species composition, functional organisation, and food‐web structure - R. M. Thompson; C. R. Townsend (New Zealand Journal of Marine and Freshwater Research, 2004)
We used standardised techniques to assemble 18 food‐webs in streams subject to four land uses; exotic pasture, native tussock, native forest, and pine plantation. There were clear differences in the algal productivity and standing crops of organic matter between the forested (native and pine) and grassland (tussock and pasture), but not within each grouping. Algal productivity was more than twice as high in the grassland sites, whereas the converse was true for organic matter standing crop. These differences in energy resources were correlated with differences in community composition and food‐web structure. Although all streams had a generalist core of species, certain species of algae and invertebrates were predictably associated with either forested or grassland sites. Food‐web structure in the forested and grassland sites was also distinct. Grassland food‐webs were complex, highly internally connected, and typified by a “triangular” shape. Forested food‐webs in contrast were less highly connected, tended to have fewer trophic levels, and were “squarer” in shape. These results provide some support for the concept that energy supply may be an important contributing factor influencing stream community structure. In terms of riparian management, the results emphasise the importance of protecting representative vegetation around streams to protect stream communities.

Tides and sea‐level variability in the south‐west Pacific from TOPEX/Poseidon - M. G. G. Foreman; R. G. Bell; J. Y. Cherniawsky; B. Beckley (New Zealand Journal of Marine and Freshwater Research, 2004)
A harmonic‐analysis technique is used to compute tidal amplitudes and phases over the south‐west Pacific Ocean from the first 300 cycles (up to November 2000) of TOPEX/Poseidon satellite altimetry. The analysis is performed along groundtracks and at track crossover locations and the resultant harmonics are shown to compare favourably with those from open‐coast sea‐level gauges and from regional and global tidal models. Small‐scale oscillations ( 2 internal tide generation, or aliasing between K 1 and semi‐annual signals. Tidal harmonics derived from satellite altimetry were used to improve the open‐sea boundary forcing for a limited‐area tidal model and produce a better validation with coastal sea‐level gauges.

Hydrogen peroxide concentrations in relation to optical properties in a fiord (Doubtful Sound, New Zealand) - Barrie M. Peake; Luke M. Mosley (New Zealand Journal of Marine and Freshwater Research, 2004)
Hydrogen peroxide concentrations are reported for the first time in the surface low salinity layer (LSL) and underlying saline layer (SL) of a fiord. Measurements were made in Deep Cove and Hall Arm in Doubtful Sound, New Zealand under contrasting climatic conditions in early summer (October; wet, windy, and dull: November; dry, still, and sunny). Steady state peroxide concentrations in the range 100–400 nM rapidly declined with depth in the LSL and across the LSL/SL interface. Spectral measurements of absorption coefficients and downwelling irradiance indicated this is largely because of high levels of chromophoric dissolved organic matter (CDOM) in the LSL filtering out the UV component ( M) .

Colonisation and growth of epiphytic algal communities on Potamogeton perfoliatus under two different light regimes - Munira Sultana; Takashi Asaeda; Jagath Manatunge; Abdurahman Ablimit (New Zealand Journal of Marine and Freshwater Research, 2004)
The composition and distribution of epiphytic algae on Potamogeton perfoliatus were studied in a controlled laboratory environment over 84 days under two light conditions. The study was based on a 2 × 2 factorial design with two light conditions (high and low, 200 and 80 μE m –2 s –1 ) and two different plant parts (apical and basal). In both light conditions, the community consisted of 18 taxa (under nine genera) of Bacillariophyceae. Amphora lineolata, Cocconeis placentula , and Diatoma hiemale were the most common and abundant species. The total algal density was significantly higher in the high light condition and on the basal plant part than in the low light condition and on the apical plant part. At termination of the experiment, basal plant parts exhibited a more uniform crust of epiphytic algae consisting of c. 95% C. placentula whereas the apical plant parts expressed a more mosaic community (under both light conditions).

Invasive species: Fish and fisheries Workshop overview, then and now - John D. Koehn; Robert M. McDowall (New Zealand Journal of Marine and Freshwater Research, 2004)
This short paper provides an overview of the “Invasive species: fish and fisheries Workshop” held in Wellington, New Zealand, 2003, with a retrospective comparison to a similar workshop held in 1989. The “then and now” comparison provides some insights into progress (or lack of it) on invasive fish issues over that 14‐year period. The workshop also highlighted the degree of commonality on this issue between Australia and New Zealand.

Shoot first, and then ask questions: A look at aquarium fish imports and invasiveness in New Zealand - R. M. McDowall (New Zealand Journal of Marine and Freshwater Research, 2004)
A risk analysis is being undertaken of threats to natural ecosystems in New Zealand from importation of aquarium fish. The literature on invasiveness reveals global concern about risks from introduced species, though the ecological bases for understanding risk potential seem imprecise and often conflicting. Moreover, whereas some principles espoused may allow identification of species that are high or low risk, these extremes form a continuum wherein the likelihood of establishment cannot be quantified. The likelihood that species, which establish, become seriously invasive is also not quantifiable. Responsible stewardship of natural ecosystems requires application of the precautionary principle. The number of fish species in the global aquarium trade is probably >5000. Many are poorly known, some undescribed, taxonomic authority for some species is obscure, and identification is problematic, especially of juveniles that lack diagnostic characters. Importation of aquarium fish is managed by the Ministry of Agriculture and Forestry (MAF), under the Biosecurity Act 1993. MAF's list of species approved for importation as aquarium fish contains c. 280 names; 178 of these names are genera, any species of which are allowed entry under the MAF protocols, e.g., the cyprinid genus Barbus , of which there are >820 species in the international database FISHBASE. Many listed species have never been imported, which would seem to bring them under provisions of the Hazardous Substances and New Organisms Act 1998. In practice this does not seem to be happening, suggesting that a review of protocols is needed to ensure that the law is being administered correctly.

Priority management actions for alien freshwater fish species in Australia - John D. Koehn; Rachel F. MacKenzie (New Zealand Journal of Marine and Freshwater Research, 2004)
In Australia, alien freshwater fish are continuing to steadily increase in number of species (reported in this paper to be 43), abundance, and distribution. In general however, their impacts are not well quantified in either environmental or economic terms and current management to reduce their impacts is limited and lacking direction. Although carp Cyprinus carpio have received some attention, very little is known about the impacts and even the distribution of most species. There is a lack of recognition of the problem, inconsistency in legislation, policy, and approaches across jurisdictions, and no nationally coordinated on‐the‐ground management actions. Where legislation and policy is available it is not always used to good effect. This paper provides a synthesis of existing knowledge of alien fishes in Australia, suggests a new management approach, and recommends priority management actions.

Marine biosecurity post‐border management: Developing incursion response systems for New Zealand - Debra M. Wotton; Chad L. Hewitt (New Zealand Journal of Marine and Freshwater Research, 2004)
New Zealand's approach to marine biosecurity has been to integrate the pre‐border, border, and post‐border management actions so as to appropriately and effectively utilise resources. Prevention is clearly better than cure, consequently pre‐border and border management is paramount. There is, however, recognition that quarantine style controls result in leaky borders. Early detection of new invaders, coupled with appropriate incursion response protocols and tools, increases the likelihood that a response will: (1) be effective; and (2) cause less collateral damage. Rapid response plans for predefined, high‐risk species allow an adaptive and targeted approach. The selected species are also the object of targeted surveillance in high incursion risk points of first entry into the New Zealand coastal environment.

Bioeconomic modelling in the development of invasive fish policy - David Choquenot; Simon J. Nicol; John D. Koehn (New Zealand Journal of Marine and Freshwater Research, 2004)
Invasive species policy is either explicitly or implicitly underpinned by the question “When should investment in managing the invasive species stop?” Bioeconomic modelling provides a quantitative framework for considering the benefits and costs of alternative levels of investment in invasive species management by linking the level of investment to the costs of intervention (control) and value of benefits derived. Control costs are typically the product of the number of individuals that have to be removed to either eradicate the invasive species or constrain it at some specified density, and the cost of removing each individual. Impact functions take a variety of forms, but in general are systematically related to the density of the managed population. Where impacts can be accounted in monetary terms (e.g., where an invasive species affects income), control costs and benefits can be directly compared and an optimal level of investment (usually that which maximises return on investment) can be identified. However, where impacts do not have a directly accessible monetary value (e.g., where an invasive species affects conservation values), benefits and costs cannot be directly contrasted. Under these circumstances, bioeconomic modelling can be used to identify management strategies that maximise the level of benefit that can be achieved for expenditure of a fixed budget (benefit maximisation), or minimise the cost of achieving a given level of benefit (cost minimisation).

Brief review of fish pheromones and discussion of their possible uses in the control of non‐indigenous teleost fishes - Peter W. Sorensen; Norm E. Stacey (New Zealand Journal of Marine and Freshwater Research, 2004)
Most species of fish rely on pheromones (chemical signals released by conspecifics) to mediate social behaviours. Three categories of pheromones can be discerned based on their function: anti‐predator cues, social cues, and reproductive cues. Each of these categories comprises pheromones that can induce “primer” effects (developmental and/or endocrinological changes) and/or “releaser” effects (strong behavioural changes). A handful of fish pheromones have been chemically identified and all are remarkably potent. Almost all are metabolic products whose production is seemingly unspecialised, insofar as they are not synthesised by specialised structures. Importantly, their potency and specificity makes them ideal candidates for use in control of both threatened (native) and unwanted (non‐indigenous) fish species. As has been so for insect control and now sea lamprey control in the North American Great Lakes, these cues could be used in many ways as part of integrated control programmes for invasive teleost fishes. Ideally, these programmes would be designed to simultaneously exploit multiple weaknesses in species’ life histories while being fully cognisant of stock‐recruitment relationships. Generally the approach would be to use a variety of pheromones to supplement and increase the efficiencies of other control strategies including the application of poisons or fish with genetic modification, trapping for removal or sterilisation, and barriers to prevent spread. Integrated pest control using pheromones appears especially practical for the common carp (Cyprinus carpio) which appears to use many of the same cues as the goldfish (Carassius auratus) and for which half a dozen pheromones have already been identified.

Use of fine‐mesh monofilament gill nets for the removal of rudd (Scardinius erythrophthalmus) from a small lake complex in Waikato, New Zealand - Keri Neilson; Rachel Kelleher; Grant Barnes; David Speirs; Johlene Kelly (New Zealand Journal of Marine and Freshwater Research, 2004)
Fine‐mesh monofilament gill nets were deployed within the three shallow lakes of the Rotopiko complex, Waikato, New Zealand to assess their potential as a tool for controlling or eradicating rudd (Scardinius erythrophthalmus) . Nets of different mesh sizes were placed at different spacings and orientations throughout the lakes for two fishing periods, to determine methodology to be used for intensive removal. Rudd were intensively netted for a further two periods and then the success of the operations was assessed. Gill nets of a 13‐mm mesh were more effective at capturing rudd when set perpendicular rather than parallel to the shore, whereas there was no significant effect of orientation in 25 mm and 38 mm nets. Comparisons of catch per unit effort (CPUE) on the first night of fishing for each fishing period showed a significant reduction in the initial CPUE as fishing proceeded. A reduction in the numbers of rudd captured was most marked in the 38 mm nets. 80% of rudd captured over a 7‐night period were caught in the first 3 nights of fishing. Post‐removal sampling using gill, fyke, and trammel nets, and an electric fishing boat, showed that rudd remained in all of the lakes following intensive removal efforts. However, relative to other methods currently available in New Zealand for control or eradication of unwanted fish, monofilament gill nets appear to be a potentially viable and cost‐effective option where ongoing control may provide sustained conservation outcomes.

Observations on the distribution and abundance of carp and native fish, and their responses to a habitat restoration trial in the Murray River, Australia - Simon J. Nicol; Jason A. Lieschke; Jarod P. Lyon; John D. Koehn (New Zealand Journal of Marine and Freshwater Research, 2004)
A native fish strategy has been initiated to rehabilitate native fish populations in the Murray‐Darling Basin, Australia. The reintroduction of large woody debris (LWD) into the Basin's large lowland rivers is one of the restoration activities in the strategy. The results from three separate studies undertaken on the Murray River between Yarrawonga and Tocumwal are presented on the relationship between carp (Cyprinus carpio) , native species, and LWD to examine whether native species and carp compete for LWD habitat. The first study reports on the relative abundance of carp and native fish in a river reach. Since 1995 carp abundance has declined, whereas the abundance of native fish populations has remained relatively constant providing little support for the hypothesis that competition for LWD habitat is having effects at the population level effects. The second study reports on the relationship between LWD, river channel position, and its use as habitat by carp and native species. A statistically significant relationship was observed between native fish, LWD, the location within a meander, and curvature of the meander. There was no statistically significant relation between carp and any of these parameters indicating that carp utilise a variety of riverine habitats, whereas native species were strongly associated with LWD. The third study reports on an experiment that tested the response of carp to the placement of new LWD habitat. The response from carp was statistically inconclusive. The combination of these studies suggest that it is unlikely that carp and native species are directly competing for LWD habitat and it is unlikely that carp will inundate restored LWD habitats and preclude native species.

Alien salmonids in Australia: Impediments to effective impact management, and future directions - Jean E. Jackson; Tarmo A. Raadik; Mark Lintermans; Michael Hammer (New Zealand Journal of Marine and Freshwater Research, 2004)
Salmonids, mainly brown and rainbow trout (Salmo trutta and Oncorhynchus mykiss) were introduced into Australia in the mid 1860s and early 1890s respectively, and now support economically valuable recreational fisheries. These alien species have established self‐sustaining populations in many aquatic environments in south‐eastern and southwestern Australia, and stocking of hatchery‐produced or wild‐caught fish in larger systems is undertaken when fisheries targets are not met (e.g., fish numbers or appropriate size). Salmonids have established self‐maintaining populations in many waters not targeted or managed as fisheries, colonising the entire catchment in cooler upland areas of Australia. These populations usually comprise a high abundance of small fish in small first‐to‐third‐order tributaries. These waters are infrequently targeted by anglers, and populations may not contribute individuals to downstream fisheries. Negative impacts of alien salmonids on native aquatic fauna (including fish, frogs, spiny crayfish), mainly through direct predation and to a lesser degree competition for resources, have been noted for over 140 years. Impacts on some faunal groups have been severe enough to eliminate entire populations and severely fragment species across their range. Despite these impacts, salmonid management is focused largely on providing improved recreational angling opportunities, whereas management of their impacts is almost non‐existent. Management of the symptom of salmonid impacts, i.e., declining native species, begins only after native species have become imperilled. This paper focuses on impediments to effective management of salmonid impacts, existing and potential management or control options, and future directions and research needs.

Risk assessment and screening for potentially invasive fishes - Cindy Kolar (New Zealand Journal of Marine and Freshwater Research, 2004)
Preventing the introduction of potentially invasive species is becoming more important as this worldwide problem continues to grow. The ability to predict the identity or range of potential invaders could influence regulatory decisions and help to optimally allocate resources to deal with ongoing invasions. One screening tool presented here, using species life history and environmental tolerances to identify potential invaders similar to past invaders, can be used to predict potential invading species. Another screening tool, genetic algorithms, can be used to predict the potential range of an invading species. Use and further development of tools such as these, that are quantitative and relatively transparent, would give managers and other decision makers more information for making better‐informed decisions.

Abstracts: Invasive species (New Zealand Journal of Marine and Freshwater Research, 2004)

New Zealand marine biosecurity: Delivering outcomes in a fluid environment - Chad L. Hewitt; Jane Willing; Allan Bauckham; A. Maria Cassidy; Camilla M. S. Cox; Liz Jones; Debra M. Wotton (New Zealand Journal of Marine and Freshwater Research, 2004)
Marine biosecurity, the protection of the marine environment from impacts of non‐indigenous species, has a high profile in New Zealand largely associated with a dependence on shipping. The Ministry of Fisheries is the lead agency for marine biosecurity and is tasked with managing the risks posed by pests and non‐indigenous marine species. Much like the terrestrial environment, multiple pathways provide ample opportunities for new species to arrive. The Marine Biosecurity Team was established in 1998, and under the Biodiversity package delivered by government, has undertaken an ambitious programme to deliver biosecurity outcomes by reducing the knowledge gaps and establishing management frameworks. A Risk Management Framework aids decision‐making and operational planning. Despite significant progress, a number of gaps have been identified in our knowledge base, capability, and capacity that require attention.

Human‐assisted dispersal of alien freshwater fish in Australia - Mark Lintermans (New Zealand Journal of Marine and Freshwater Research, 2004)
Approximately 34 alien fish species have established populations in Australian freshwaters with a further 53 native fish species translocated within the country. Twelve pathways of human‐assisted dispersal for freshwater fish have been identified in Australia, and each is discussed with examples given. The major pathway has been the aquarium or ornamental fish industry, with 22 of the 34 alien species originating from this source. Management actions to date have largely focused on eradication or mitigation, with little national or interstate coordination of efforts. Future management actions are suggested, with priorities being public and industry education and the development of coordinated strategies based on pest management principles.

Distribution and impacts of introduced freshwater fishes in Western Australia - David L. Morgan; Howard S. Gill; Mark G. Maddern; Stephen J. Beatty (New Zealand Journal of Marine and Freshwater Research, 2004)
This paper presents comprehensive distributional data, from over 1300 sites, on introduced freshwater fishes in Western Australia. Currently, there are 10 species of introduced freshwater fish established in the inland waters of Western Australia. Most of the introduced fishes found here are those that have formed feral populations elsewhere in the world, and include members of the Salmonidae, i.e., rainbow trout (Oncorhynchus mykiss) and brown trout (Salmo trutta); Cyprinidae, i.e., goldfish (Carassius auratus) and carp (Cyprinus carpio); Poeciliidae, i.e., mosquitofish (Gambusia holbrooki) , one‐spot livebearer (Phalloceros caudi‐maculatus) , guppy (Poecilia reticulata) , and swordtail (Xiphophorus hellerii); Percidae, i.e., redfin perch (Perca fluviatilis) , and Cichlidae, i.e., Mozambique mouthbrooder or tilapia (Oreochromis mossambicus) . More recently, the eastern Australian silver perch (Bidyanus bidyanus) (Terapontidae), which was introduced for aquaculture, has been captured in the Swan River near Perth. It is not known whether this population is self‐maintaining. The majority of introduced species are confined to the south‐west, although four and one species have been recorded from the Pilbara and Kimberley, respectively. Some species are extremely common and widespread, e.g., G. holbrooki and P. fluviatilis , whereas others are far more restricted and may be confined to between one and three catchments, e.g., C. carpio, P. caudimaculatus, P. reticulata, X. hellerii, O. mossambicus , and B. bidyanus . The impact of these introduced fishes on native species varies, but ranges from predation, e.g., O. mykiss, S. trutta, G. holbrooki , and P. fluviatilis , to aggressiveness, e.g., G. holbrooki, X. hellerii , and O. mossambicus , and competition for food and habitat.

Verifying invasive marine fish species using molecular techniques: A model example using triplefin fishes (Family Tripterygiidae) - Anthony J. R. Hickey; Shane D. Lavery; Sarah R. Eyton; Kendall D. Clements (New Zealand Journal of Marine and Freshwater Research, 2004)
Molecular techniques can resolve many questions concerning the identification and origins of invasive marine species. We used a molecular taxonomy based on the mitochondrial control region (mtCR) to identify the origin of three cryptogenic triplefin species (Family: Tripterygiidae) found in two Australian ports—Port Phillip Bay, Melbourne and the Derwent Estuary, Hobart. DNA was extracted from Australian specimens of Forsterygion varium, F. lapillum , and Grahamina gymnota , and PCR (polymerase chain reaction) fragments of the mitochondrial control region (mtCR, c. 400 bp) were amplified, sequenced, and aligned to a reference alignment containing 23 endemic New Zealand triplefin species. Multiple specimens were sequenced for Australian F. varium , and G. gymnota , and the sequences were aligned to data sets from conspecific specimens collected around New Zealand. The sequences from Australian specimens of F. varium and G. gymnota consisted of only one and two haplotypes, respectively. Haplotypes of all three Australian species nested among New Zealand conspecific haplotypes, and the single Australian F. varium haplotype was shared with two southern New Zealand individuals. The low genetic diversity in two of the Australian triplefin populations of F . varium and G. gymnota and their close genetic relationship to New Zealand populations strongly suggests recent introductions from New Zealand to Australia.

Gambusia in New Zealand: Really bad or just misunderstood? - Nicholas Ling (New Zealand Journal of Marine and Freshwater Research, 2004)
Mosquitofish ( Gambusia spp.) have been spread throughout most of the temperate world during the 20th Century as biological control agents for mosquitoes. However, in many areas of introduction these small aggressive fish have been implicated in the displacement or exclusion of native species of fish and amphibians. Those species most affected are small, surface‐feeding, littoral‐zone fishes and the egg and larval stages of amphibians. In New Zealand, the western mosquitofish, Gambusia affinis , was introduced at Auckland in 1930 and has since spread throughout much of the North Island with recent introductions to the northern South Island. They have been implicated in the decline of dwarf inanga, Galaxias gracilis , and may affect recruitment of black mudfish, although the continued abundance of inanga, mudfish, and other small‐bodied natives at sites long inhabited by Gambusia implies that competition or predation by the latter may be minimal and that Gambusia occupies an underutilised niche in New Zealand aquatic environments. The ability of Gambusia to cause ecosystem alteration by selective removal of invertebrate grazers is possibly of greater concern in New Zealand than any perceived threat to native fishes.

Aquaculture trials of the New Zealand bath‐sponge Spongia ( Heterofibria ) manipulatus using lanterns - Michelle Kelly; Sean Handley; Mike Page; Paul Butterfield; Bruce Hartill; Shane Kelly (New Zealand Journal of Marine and Freshwater Research, 2004)
A submarine lantern system was trailed in the aquaculture of explants of the endemic New Zealand bath‐sponge Spongia ( Heterofibria ) manipulatus (Demospongiae: Dictyoceratida: Spongiidae) at four New Zealand sites, two in the Marlborough Sounds and two off Coromandel Peninsula. The main objectives were to compare growth rates of explants at different sites, compare these with those of control sponges, and to assess the utility of these lanterns for the culture of this species. After a period of 13 months, sponges at exposed Bonne Point in the Marlborough Sounds were on average 73% larger in estimated volume than at the start of the experiments. Growth rates of explants at exposed Port Charles, Coromandel, showed no significant change over the study period, although positive growth over spring 2003 was evident. Sponge explants at sheltered Wairangi Inlet and Kennedy Bay, in the Marlborough Sounds and Coromandel, respectively, did poorly, with most explants regressing in size and becoming moribund. Growth rates varied considerably between individuals at each location. Implications of the growth rate characteristics of S . ( H .) manipulatus , and the design and construction of the aquaculture lantern, for the future commercial production of this species are discussed.

Water quality in low‐elevation streams and rivers of New Zealand: Recent state and trends in contrasting land‐cover classes - Scott T. Larned; Mike R. Scarsbrook; Ton H. Snelder; Ned J. Norton; Barry J. F. Biggs (New Zealand Journal of Marine and Freshwater Research, 2004)
River water quality in New Zealand is at great risk of impairment in low elevation catchments because of pervasive land‐use changes, yet there has been no nationwide assessment of the state of these rivers. Data from the surface‐water monitoring programmes of 15 regional councils and unitary authorities, and the National River Water Quality Network were used to assess the recent state (1998–2002) and trends (1996–2002) in water quality in low‐elevation rivers across New Zealand. Assessments were made at the national level, and within four land‐cover classes (native forest, plantation forest, pastoral, and urban). Finer‐scaled assessments were made by subdividing the large number of pastoral sites into six climate classes, and seven stream orders. At the national level, median concentrations of the faecal indicator bacterium Escherichia coli , and dissolved inorganic nitrogen and dissolved reactive phosphorus exceeded guidelines recommended for the protection of aquatic ecosystems and human health. Water quality state varied widely within land‐cover classes: E. coli and dissolved nitrogen and phosphorus concentrations in the pastoral and urban classes were 2–7 times higher than in the native and plantation forest classes, and median water clarity in the pastoral and urban classes was 40–70% lower than in the native and plantation forest classes. Water quality state in the pastoral class was not statistically different from that of the urban class, and water quality state in the plantation forest class was not statistically different from that of the native forest class. Significant trends in low‐elevation rivers were limited to four parameters: flow (trending down in all instances), and temperature, clarity, and conductivity (trending up in all instances). The trends in flow, temperature, and clarity were apparent at the national scale, and within the pastoral class. The magnitudes of these trends were very low, corresponding to changes of ≤0.5%/ year in parameter medians.

Adsorption and transport of cadmium and rhodamine WT in pumice sand columns - Liping Pang; Murray Close; Helen Greenfield; Greg Stanton (New Zealand Journal of Marine and Freshwater Research, 2004)
The transport and attenuation of cadmium (Cd) and rhodamine WT (RWT) in a pumice sand aquifer media was investigated using column experiments to study a scenario of point‐source contamination. A pore‐water velocity of 1.7–1.8 m/day, which is a typical field groundwater velocity in a pumice sand aquifer system, was applied to triplicate columns. A pulse of a solution containing Cd and RWT, together with the conservative tracer tri‐tiated water ( 3 H 2 O) at pH = 7, was introduced into the columns. Experimental results showed that concentration breakthrough curves (BTCs) of 3 H 2 O were symmetrical and fitted well into an equilibrium model. In contrast, BTCs of Cd and RWT were asymmetrical with significant tailings and fitted well with a two‐site adsorption/desorption model. The symmetric 3 H 2 O BTCs suggest that physical non‐equilibrium was absent in the experimental system, therefore the asymmetrical BTCs of Cd and RWT were attributed to chemical non‐equilibrium. Modelling results showed that, in comparison with 3 H 2 O, Cd was apparently retarded by 101–108 times in pumice sand aquifer media (apparent adsorption coefficient 7.33–9.24 ml/g) and underwent a mass loss of 20–30% that was probably because of precipitation of CdCO 3 . As CdCO 3 is extremely insoluble, Cd precipitation would be irreversible and therefore it would not contribute to the tailing of the Cd BTCs. The experimental results suggest that the adsorption and desorption of Cd in pumice sand aquifer media in hydrodynamic conditions was a kinetic process. Cd desorption rates were two orders‐of‐magnitude slower than its adsorption rates. This resulted in a prolonged mean residence time for Cd in pumice sand aquifer media, which was 10–12 days in the 18‐cm‐long columns under a flow velocity of 1.7–1.8 m/day. Since the mean residence time is only indicative for the arrival of the central of mass in a contaminant BTC, the time required for the total disappearance of Cd will be much longer than the mean residence time because of the significantly long tailing of the BTC. This implies that natural attenuation of Cd from a contaminated pumice sand aquifer would take a time period from decades to centuries. Batch isotherm experiments were also carried out to obtain Cd adsorption coefficients at equilibrium conditions. In comparison with the column results obtained from non‐equilibrium conditions, adsorption coefficients of 20 ml/g obtained from the batch equilibrium experiments were 2–3 times higher for Cd. This finding suggests that care should be taken when using batch adsorption isotherm results to predict field problems because the delay in the appearance of contaminants in drinking water wells and springs could be overestimated. In comparison with 3 H 2 O, RWT was retarded 5–7 times and had BTCs that were significantly more spread out. Hence the use of RWT to indicate groundwater flow in pumice sand aquifers will underestimate groundwater velocity and overestimate aquifer dispersivity. About 4–14% of RWT mass was lost during its transport, probably because of the irreversible adsorption of isomer 2 (one of two major components of RWT) dye onto the aquifer sand.

Morphology and biology of Polydora rickettsi (Polychaeta: Spionidae) from Chile - Vasily I. Radashevsky; César A. Cárdenas (New Zealand Journal of Marine and Freshwater Research, 2004)
The spionid polychaete Polydora rickettsi is primarily a borer in various calcareous substrata in the eastern Pacific. Redescription of the species from the type locality in Mexico is required to better understand its distribution. In Chile, females and males become mature after growth to c. 60 segments. Sex allocation in the population is close to 1:1. Gametes develop along segmental blood vessels in middle segments. Spermatogonia proliferate in temporary testes and the rest of spermatogenesis occurs in the coelomic cavity. On their release through metanephridial segmental organs, longheaded spermatozoa are packed in filiform spermatophores. Females store inactive spermatozoa in paired seminal receptacles on the dorsal side of fertile segments. Oogenesis is mostly intraovarian. Females deposit up to 4150 eggs into 65 capsules which are joined to each other in a string. Each egg capsule is attached by two stalks to the inner wall of the burrow and contains up to 65 eggs c. 95 μm in diameter. Most eggs give rise to larvae which develop inside egg capsules until the 3‐segment stage, then hatch and continue development in sea water, feeding on plankton. Fully developed 17–18‐seg‐ment larvae are able to settle and metamorphose. They have one pair of phaosomes and three pairs of black eyes on the prostomium, provisional proto‐nephridia in segments 1 and 2, paired dorsal melanophores from segment 3 onwards, lateral melanophores on segment 2 and from segment 10 onwards, yellow pigment in the wall of posterior gut, glandular pouches from segment 6 onwards, short branchiae on segments 7–11, gastrotrochs on segments 3, 5, 7, 10, 13, 15, and 17, one pair of provisional modified bristles and two or three falcate spines of a “quasi‐adult” kind in segment 5. Development of the “quasi‐adult” spines is described for the first time in polydorid larvae.

Trophic basis of production for a mayfly in a North Island, New Zealand, forest stream: Contributions of benthic versus hyporheic habitats and implications for restoration - Kevin J. Collier; Aslan E. Wright‐Stow; Brian J. Smith (New Zealand Journal of Marine and Freshwater Research, 2004)
The leptophlebiid mayfly Acantho‐phlebia cruentata (Hudson) is restricted to the North Island and some associated offshore islands of northern New Zealand where it commonly occurs in benthic and hyporheic habitats of forested streams. We investigated: (1) life history; (2) secondary production in benthic and hyporheic habitats; and (3) major energy sources contributing to nutrition and production of this species in a pristine forest stream. Most nymphal size classes were present throughout the year, and emergence extended over several months, peaking from February to April. Despite apparently having extended emergence and recruitment periods, Acanthophlebia exhibited a predominantly univoltine life history. Annual benthic production (calculated by the size‐frequency method) was 0.318 g dry mass (DM) m –2 year –1 , compared to 4.601 g DM m –2 year –1 in high‐density benthic habitats at the tails of pools, and 34.476 g m –3 year –1 for colonisation baskets set at 15–45 cm deep in the substratum. On a habitat weighted basis averaged out over the entire sampling reach, it was estimated that 76% of annual production occurred in hyporheic habitats >10 cm below the streambed surface. Gut contents were dominated by fine particulate matter (FPM) ≤75 μm and larger inorganic material on all dates in individuals from both benthic and hyporheic habitats. Fungi were relatively abundant in guts of benthic animals collected on some dates, whereas spores and pollen were relatively common food items in both habitats on occasions. Analysis of the trophic basis of production, based on gut contents and assumed assimilation and net production efficiencies, indicated that benthic secondary production was supported largely by fungi (48% of production) and FPM (37%), whereas FPM supported a higher level of hyporheic production (52%) than fungi (27%). Although stable carbon isotope values suggested dependence on epilithon, the enriched δ 15 N values for this food source implicated the involvement of a microbial loop whereby a substantial proportion of Acanthophlebia nutrition appeared to be derived from heterotrophs growing in FPM and epilithon that had assimilated dissolved organic carbon. This study has highlighted the significant role that hyporheic habitats can play in the ecology of Acanthophlebia populations in pristine native forest streams. Re‐establishment of hyporheic function would appear to be an important component of stream restoration work to enable the successful recolonisation of Acanthophlebia populations at sites where they historically occurred.

Diel patterns of feeding and prey selection in giant kokopu ( Galaxias argenteus ) - Eric A. Hansen; Bruno O. David; Gerard P. Closs (New Zealand Journal of Marine and Freshwater Research, 2004)
We examined diel variation in prey selection by giant kokopu, Galaxias argenteus , in relation to diel variation in the abundance of drifting invertebrates in a second order stream in Otago, New Zealand in summer. Clear differences in both the quantity and composition of prey consumed was evident. Greater numbers of aquatic insects were consumed at night relative to the day, whereas more terrestrial insects were consumed by day relative to the night. Giant kokopu were selective in the prey consumed. Trichoptera dominated giant kokopu diet at night even though drift samples collected at night were dominated by Deleatidium mayflies. Results suggest that giant kokopu feed actively during night and day in summer, and that prey selection is influenced by interactions between factors including prey availability, prey characteristics and light.

Water and sediment chemistry of Sutton Salt Lake, east Otago, New Zealand - D. Craw; S. Beckett (New Zealand Journal of Marine and Freshwater Research, 2004)
The Sutton Salt Lake is the only saline lake in New Zealand, and has formed in a windy cool‐temperate maritime climate. Consequently, the lake is distinctly different from most of the world's saline lakes that form in arid continental settings. Sutton Salt Lake forms annually in a shallow (5 m) bedrock‐floored depression c. 50 km from the nearest coast. The site receives c. 500 mm/year rainfall compared with coastal rainfall of near 1000 mm/year because of a minor rain‐shadow effect of coastal hills. Surface evaporation rate is high (c. 700 mm/ year) because of frequent strong winds. Sediments on the lake floor are derived by rain and wind erosion of the surrounding quartzofeldspathic schist bedrock, with a contribution from organic sources, particularly ostracods, and evaporative halite. The sediments have a higher proportion of phyllosilicates (muscovite, kaolinite, and chlorite) than the source rocks because of differential transport of these minerals into the lake depression. Lake water is entirely derived from rain, rather than groundwater, and the lake waters have had minimal chemical interaction with bedrock. Lake water pH is near 9 and pH of pore waters in drying lake sediments is near 8, compared with a pH near 7 for regional surface and ground waters. When full, the lake has salinity about one quarter to one third of that of sea‐water, and ion ratios are similar to sea‐water. The lake salinity is derived from marine aerosols in rainwater concentrated by c. 20 000 evaporation and refilling cycles in the lake depression.

Age determination, validation, and growth of blue cod Parapercis colias , in Foveaux Strait, New Zealand - Glen Carbines (New Zealand Journal of Marine and Freshwater Research, 2004)
Blue cod ( Parapercis colias ) is an important inshore commercial and recreational fish species in the southern islands of New Zealand, and estimates of their growth rate, age at maturity, and longevity are required for fisheries management. This study provides validation and comparisons of ageing methodologies for blue cod in Foveaux Strait, Southland. Sectioned otoliths showed a consistent banding pattern, and counts of these had good consistency between readers. Scales, broken and burnt, and whole otoliths gave lower band counts than equivalent sectioned otoliths counts. Blue cod otoliths were small, and otolith weights and lengths showed no relationship with sectioned otolith band counts. Marginal increment analysis provided a partial validation of ages estimated from sectioned otoliths, and oxytetracycline marking completed the validation for blue cod over 300 mm total length. Fin spines also showed promise as an excellent and non‐lethal ageing tissue. Blue cod growth in Foveaux Strait was then described and compared to previous studies, which are likely to have underestimated ages because of the use of broken and burnt and whole otoliths.

Deep‐water bryophyte records from New Zealand lakes - M. D. de Winton; J. E. Beever (New Zealand Journal of Marine and Freshwater Research, 2004)
A review of bryophyte records from New Zealand lakes showed a “deep‐water” assemblage occurred at ≥ 10 m depths within 16 lakes all of which possessed high water clarity (1/ K d >3). Bryophyte depth limits ranged from 12 to 70 m. Depth limit was significantly related to water clarity and extended to where the level of irradiance was 0.2–1% of light incident on the lake surface. Deep‐water bryophytes were generally absent from lakes where large populations of freshwater crayfish occurred, and from sites with physical disturbance. Between 34 and 42 bryophyte taxa were recorded, with some identifications incomplete because of unusual morphology. Although some taxa are known to be aquatic, others have previously been regarded as typically terrestrial or paludal. Deep‐water bryophytes were well represented in New Zealand lakes compared with records from elsewhere. Significant threats to this unusual plant assemblage are eutrophication accompanied by declining water clarity.

Deep New Zealand. Blue water, black abyss. By PeterBatson. Published in 2003 by Canterbury University Press, Christchurch, New Zealand. 240 p. Softcover. ISBN 1–877257–09–5 Price: NZ#DL49.95.The living reef: the ecology of New Zealand's rocky reefs. Edited by NeilAndrew and MalcolmFrancis. Published in 2003 by Craig Potton Publishing, P.O. Box 555, Nelson, New Zealand (http//www.craigpotton.co.nz). 283 p., hardcover. ISBN: 1–877333–02–6. Price: NZ$59.95 (orders: info@cpp.co.nz).River mechanics. By Pierre Y.Julien. Published in 2002 by Cambridge University Press, Shaftesbury Road, Cambridge, CB2 2RU, United Kingdom (http://uk.cambridge.org/). 454 p., hardback (ISBN: 0521562848) and softback (ISBN: 0521529700). Price: £80.00 (hardback); £33.00 (softback) (orders: directcustserve@cambridge.org). - G. Robin South; Russell Millar; Graeme Smart (New Zealand Journal of Marine and Freshwater Research, 2004)

A preliminary investigation of biosecurity risks associated with biofouling on merchant vessels in New Zealand - Ashley D. M. Coutts; Michael D. Taylor (New Zealand Journal of Marine and Freshwater Research, 2004)
Biofouling on international vessels is an important mechanism for the inadvertent transfer of non‐indigenous marine species around the globe. This paper describes the nature and extent of biofouling on 30 merchant vessels (ranging from 1400 to 32 000 gross registered tonnes) based on analysis of hull inspection video footage collected by two New Zealand commercial diving companies. A new method for measuring biofouling communities is applied, which aims to incorporate the potential for various hull locations to house non‐indigenous marine species. Our analysis revealed that out‐of‐service vessels and vessels plying trans‐Tasman routes possessed greater levels of biofouling than more active vessels. Dry‐docking support strips and sea‐chest gratings generally had the highest levels of biofouling and may pose relatively high biosecurity risks. Any future biosecurity surveillance should target these hull locations for non‐indigenous species.

Aspects of the reproductive phenology of Lessonia trabeculata (Laminariales: Phaeophyceae) from three populations in northern Chile - Fadia Tala; Mario Edding; Julio Vásquez (New Zealand Journal of Marine and Freshwater Research, 2004)
Lessonia trabeculata is a brown seaweed inhabiting the rocky subtidal zone along the coast of central and northern Chile, where it is the dominant kelp, and an important species in community structure. Morphological and reproductive aspects of this alga are dependent on environmental conditions and geographic distribution, and the present study gives data on its reproductive periodicity. The reproductive phenology for three populations from northern Chile (29–30°S) was evaluated by means of seasonal examination of morphological and reproductive characteristics of both macroscopic sporophytes and microscopic gametophytes. Comparative laboratory cultures of spores were made to determine seasonal differences in their capacity to produce viable plants. This species is perennial, and demonstrates year‐round presence of reproductive tissues, although showing variation in reproductive phenology over time and among populations. The size of blades increases in spring and summer, whereas its reproductive potential (e.g., area and proportion of the reproductive tissue and the release of spores) increases in autumn. Culture experiments showed that spring and summer reproductive tissue released zoospores which had low germination rates compared to those of autumn and winter, and which produced female gametophytes of low fertility. The population differences depended on the character analysed and the season of the year. The development of both phases of the life cycle of L. trabeculata may be influenced by the local environmental conditions and their seasonal changes, and were expressed as morphological and/ or reproductive changes in the plants. A better understanding of the seasonal adaptations may be obtained if future comparisons are made between widely separated populations or between individuals from the extremes of geographic distribution of the species.

Description and genetic identification of the early life‐stages of Notolabrus fucicola and N. tetricus from Tasmanian waters, Australia, with notes on their newly‐settled juveniles - D. C. Welsford; A. R. Jordan; A. J. Smolenski (New Zealand Journal of Marine and Freshwater Research, 2004)
The early life‐stages of Notolabrus fucicola and N. tetricus are described and illustrated. Developmental stages examined included eggs and yolk‐sac larvae reared in aquaria and post‐settlement juveniles collected from artificial habitats in the coastal waters of eastern Tasmania, Australia. Larvae were similar to other labrids previously described. Species‐specific characters were only evident after settlement, and with the development of scales at c. 15 mm standard length. A molecular assay, based on restriction fragment length polymorphism (RFLP), enabled the discrimination of all five of the closely‐related wrasses in the genera Notolabrus, Pseudolabrus, Dotalabrus , and Pictilabrus found on the east coast of Tasmania. This study constitutes the first description of the early life‐stages of Notolabrus spp. from temperate Australia.

National survey of pesticides in groundwater in New Zealand—2002 - Murray E. Close; Mark J. Flintoft (New Zealand Journal of Marine and Freshwater Research, 2004)
A total of 133 wells throughout New Zealand were sampled for the 2002 National Survey of Pesticides in Groundwater. The survey objectives were to provide a national overview of pesticides in New Zealand's groundwater systems, to examine changes with time from earlier surveys, and to examine factors linked with pesticide contamination. The samples were screened for atrazine in the laboratory using an ELISA test kit and, as a result of this screening, samples positive for atrazine were analysed for 58 different pesticides using gas chroma‐tography‐mass spectrometry (GCMS). Blind duplicate samples (6%) and quality control samples (17% of the negative ELISA screen samples) were also analysed by GCMS. Three regional councils carried out their own pesticide surveys around the same time but submitted the samples for analysis to a different laboratory. Their results are included to give a national perspective. Pesticides were detected in 28 wells (21%), with 13 wells (10%) having two or more pesticides detected. There were one or more wells with pesticides detected in nine of the 15 regions. No pesticides were detected in wells from the Northland, Hawke's Bay, Manawatu‐Wanganui, Taranaki, Wellington, and West Coast regions. None of the wells in the 2002 survey had pesticides at levels above the maximum acceptable value (MAV) for drinking water (Ministry of Health 2000). Twenty‐one different pesticides were detected, including two triazine metabolites, usually at very low concentrations. Only three detections were at levels exceeding 1 mg m –3 . Thirty‐nine out of the 58 pesticide detections (67%) belonged to the triazine group. As would be expected there were significant differences between wells with and without detected pesticides in factors associated with well or screen depth, and depth of water above the screen. In addition, lower groundwater temperatures and higher nitrate levels were associated with the increased detection of pesticides. A comparison with earlier surveys indicates that pesticide detections have been relatively stable over the past 12 years. After an adjustment to common reporting limits (reporting limits were substantially lower during later surveys), the overall frequency of pesticide detections were as follows: 1990 (7%), 1994 (13.6%), 1998 (11%), and 2002 (9%).

Predicting growth and mortality of brown trout ( Salmo trutta ) in the Goulburn River after mitigation of cold‐water discharge from Lake Eildon, Australia - Paul Brown (New Zealand Journal of Marine and Freshwater Research, 2004)
Published empirical models for growth and natural mortality were examined to investigate some of the potential effects on brown trout populations of flows managed to increase river temperatures downstream of a large reservoir. Models were fitted to length‐at‐age and size‐at‐maturity observations for brown trout ( Salmo trutta ) and to 3 years of river temperature data, to predict growth and mortality. Best fits of the models suggested that both energy intake and temperature regime currently limit growth. Flow management scenarios for the Goulburn River downstream of Eildon Reservoir, Australia, that increase the average daily river temperature by 2 and 4°C, substantially reduce the potential for brown trout growth. An average daily 2°C increase reduced the potential maximum size of brown trout by 4–38% and increased the time taken to reach 300 g by up to 31%. An average 4°C rise reduced the potential maximum size of brown trout by 30–43% and increased the time taken to reach 300 g by 66–144%. Existing models of the effects of environmental temperature on rates of natural mortality also suggest that raised water temperature will result in increased brown trout mortality rates although uncertainty associated with empirical temperature‐mortality models is high. Currently the Goulburn River downstream of Eildon supports a socially and economically valuable recreational brown and rainbow trout fishery. The present study shows that the quality and quantity of brown trout that would be available under strategies proposed to mitigate cold‐water flows are unlikely to continue to sustain a viable, high quality trout fishery.

Ostreobium quekettii (Ostreobiaceae: Chlorophyceae) invading the barnacle Acasta sp. (Pendunculata: Acastinae), endozoic in the octocoral rumphella suffruticosa (Alcyonacea: Gorgoniidae) from Fiji, south pacific - K.‐D. Feussner; P. A. Skelton; G. R. South; P. Alderslade; W. Aalbersberg (New Zealand Journal of Marine and Freshwater Research, 2004)
The eukaryotic alga Ostreobium quekettii (Ostreobiaceae: Chlorophyceae) is reported from Fiji for the first time. It is found creeping over the calcareous plates of dead specimens of species of a barnacle genus Acasta (Pendunculata: Acastinae), which was endozoic in the gorgonian Rumphella suffruticosa . The barnacles are lodged in cavities in the coenenchyme of the gorgonian, mostly in the vicinity of colonial branching points. There is little external evidence of the location of the barnacles where the gorgonian tissue is thick, but where it is thin, prominent galls are visible. There is no evidence that the barnacle or algal association causes stress to the host, which was otherwise healthy in appearance. The presence of the algae would appear to be associated with the occurrence of the barnacles.

Assessment of antibiotic activity in surface water of the lower Taieri Plain and impacts on aquatic bacteria in Lake Waipori, South Otago, New Zealand - Marc Schallenberg; Amy Armstrong (New Zealand Journal of Marine and Freshwater Research, 2004)
Veterinary antibiotics are widely used in New Zealand and around the world to treat bacterial infections and for non‐therapeutic use as growth promoters. There is growing concern that unmetabolised antibiotics pass through stock and enter the environment, facilitating antibiotic resistance in pathogenic bacteria and harming aquatic ecosystems. Bioassay experiments showed that filtered water from an agricultural drain reduced the abundance of aquatic bacteria in Lake Waipori, a shallow coastal lake, whereas most other planktonic organisms were not inhibited. This result was consistent with the presence in the drain water of bacte‐riolytic antibiotics (e.g., penicillin). Further experiments were conducted to examine the effects of admixtures of water from the same agricultural drain both on the abundance and respiration rate of aquatic bacteria in the lake. One of four experiments showed inhibition of bacterial respiration consistent with the presence of bacteriostatic antibiotics (e.g., tetracyclines, aminoglycosides, macrolides) in the drain water. No further significant bacteriolytic effects were observed. A mixture of commonly used antibiotics was not consistently effective at reducing bacterial abundance or inhibiting bacterial respiration in lake water. Although we found evidence of antibacterial activity in the drain water this was intermittent, indicating either that antibiotic inputs to the drain were also intermittent, that other environmental factors intermittently affected the potency of antibiotics in the drain water, and/or that aquatic bacteria exhibited temporally variable resistance to antibiotics.

Jaw malformation in cultured yellowtail kingfish (Seriola lalandi) larvae - Jennifer M. Cobcroft; Patricia M. Pankhurst; Carolyn Poortenaar; Bob Hickman; Mike Tait (New Zealand Journal of Marine and Freshwater Research, 2004)
Several jaw malformations are common in cultured finfish larvae. Hatchery‐reared yellowtail kingfish (Seriola lalandi) larvae were cleared and stained to examine cartilage and bone structure of the jaw. One malformation, characterised by a lowered hyoid arch, was present in kingfish larvae on days 4 and 8 post‐hatching, but not on day 12. A different malformation was present in larvae on day 16, typified by abnormal positioning of the lower jaw and hyoid arch, and breakage of the Meckel’ s cartilage. Evidence of jaw malformations as early as day 4 suggests that broodstock nutrition may be a factor in the jaw malformation of kingfish larvae, but other potential causes are environmental factors in culture and larval nutrition.

Invertebrate community dynamics in soft‐bottomed streams of northern New Zealand: A spatio‐temporal hierarchy - Kevin J. Collier (New Zealand Journal of Marine and Freshwater Research, 2004)
Environmental and macroinvertebrate data collected across a range of spatial and temporal scales are synthesised to investigate factors influencing invertebrate community structure and composition in soft‐bottomed streams ( 50% of streambed substrata in sand‐silt) of northern New Zealand. A total of 75 macroinvertebrate taxa was recorded from sand‐silt substrata at 13 Waikato sites (54 taxa) and 8 Northland sites (53 taxa) where faunas were dominated by Ephemeroptera, Trichoptera, Chironomidae, and Mollusca. Differences in upstream geology, climate, land cover, and hydrology, potentially coupled with biogeographic factors, appeared to contribute to a regional separation in invertebrate community structure (taxa presence‐absence). In the Waikato, site‐specific conditions had a stronger influence on community structure and composition than substratum (sand‐silt, macrophyte or wood). However, within sites, substratum type had strong effects on macroinvertebrate communities that persisted through time. On macrophytes, faunal composition varied considerably over time and among sampling patches, reflecting phenological shifts in the species and biomass of plants present, successional changes in invertebrate taxa, and micro‐scale variations in water velocity. Macrophytes can provide important sites for energy transfer, although pathways leading to invertebrate nutrition appeared site‐specific and temporally variable. Collectively, these data point to a spatio‐temporal hierarchy of factors that influence invertebrate community structure and composition in soft‐bottomed streams. The major differences compared with stony streams occur at the micro‐ to meso‐scales, with greater significance of non‐benthic substrata (wood and macrophytes) as invertebrate habitat and sites of energy transfer in soft‐bottomed streams, and the temporally variable influence of changing macrophyte biomass on local hydraulic conditions and water quality. To help reduce the effects of high spatial and temporal variability and obtain a representative picture of reach‐scale conditions for stream health assessment purposes, long‐term invertebrate monitoring of soft‐bottomed streams should incorporate all velocity and substrata conditions, and aim to collect samples at a consistent stage of the macrophyte phenological cycle.

Erratum (New Zealand Journal of Marine and Freshwater Research, 2004)

Role of microzooplankton grazers in the subtropical and subantarctic waters to the east of New Zealand - Julie Hall; Karl Safi; Andrea Cumming (New Zealand Journal of Marine and Freshwater Research, 2004)
Subtropical and subantarctic surface waters to the east of New Zealand were sampled in four seasons over a period of 3 years to evaluate the importance of the microzooplankton as grazers of the phytoplankton community. Subtropical waters (STW) to the north were warm with high salinity and seasonal macronutrient limitation. Subantarctic waters (SAW) to the south were colder, with lower salinity, high macronutrient concentrations and chlorophyll a concentrations between 0.20 and 0.28 μg litre‐ 1 . In the STW, phytoplankton showed a typical seasonal pattern for macronutrient‐limited waters, with biomass dominated by large phytoplankton and a chlorophyll a maximum of 1.4 μg litre– 1 in spring. Microzooplankton biomass varied from 4.5 μg carbon (C) litre ‐1 in the STW in winter, to 13.8 μg C litre ‐1 in the SAW in winter with the hetero‐trophic flagellates contributing between 22% and 78% of the biomass. In spring and winter in the STW, only 73% of the primary production was grazed by the microzooplankton compared with over 100% in autumn and summer. In contrast, over 100% of the primary production was consumed in all seasons by the microzooplankton in SAW. In the SAW in all seasons and the STW in summer and autumn, microzooplankton grazing on phytoplankton dominated the organic matter fluxes from the phytoplankton population. During these periods the picophytoplankton contributed a significant proportion of the phytoplankton biomass.

Fish species composition on seamounts and adjacent slope in New Zealand waters - D. M. Tracey; B. Bull; M. R. Clark; K. A. MaCkay (New Zealand Journal of Marine and Freshwater Research, 2004)
Datasets from deep‐water fisheries abundance surveys on the commercially important species—orange roughy (Hoplostethus atlanticus) , smooth oreo (Pseudocyttus maculatus) , and black oreo (Allocyttus niger) —were used to compare fish fauna between seamounts in 10 different parts of the New Zealand region. For five of these areas, fauna was also compared between the seamounts and nearby areas of the relatively flat slope. Dominant species were listed for each area. Diversity was compared between seamount complexes, and between seamount and slope areas. Differences between the species taken in different seamount areas were investigated using similarity analysis. Total species richness was similar in all seamount regions, but mean species richness was found to be much higher in southern areas. Species richness was consistently higher on the relatively flat slope than on seamounts. Five seamount areas south of 41°S were found to have similar fish fauna, as compared with three seamount areas north of 41°S which were different from the southern areas and from each other.

Some effects of river discharges and currents on phytoplankton in the sea off Otago, New Zealand - Graeme J. Haywood (New Zealand Journal of Marine and Freshwater Research, 2004)
Major rivers on the south‐eastern coast, South Island, New Zealand create plumes that are deflected north between the Southland Current and the coast. Surveys of the continental shelf water mass off the Otago coast over a 2‐year period, May 1996‐April 1998, confirmed that when the Southland Current surfaced it contained less chlorophyll a than mixed water subject to terrestrial influence, implying that river‐borne nutrients stimulated primary production in the mixed water. The greatest boost occurred in winter when diatom abundance increased. The band of chlorophyll‐rich water extended through the photic zone and was several kilometres wide suggesting that riverine influence on marine biomass is substantial. In summer, the Southland Current often lay beneath oceanic water, with no increase in chlorophyll a concentration in the overlying water, due possibly to heavy grazing by zooplankton. In summer 1997–98, seawater temperatures were higher and phytoplankton biomass lower than in summer 1996–97, consistent with a strong El Niño event in the Pacific Ocean.

Coral‐inhabiting barnacles (Cirripedia: Balanomorpha: Pyrgomatinae) from the Kermadec Islands and Niue Island, New Zealand - Yair Achituv (New Zealand Journal of Marine and Freshwater Research, 2004)
Four species of coral‐inhabiting barnacles (Pyrgomatinae) are reported. A single species, Cantellius septimus , was found in Montipora from the Kermadec Islands; this represents the most southerly record of coral‐inhabiting barnacles. The material from the Niue Island contains three species, Savignium crenatum, Trevathana dentata , and a new species, Trevathana niuea n. sp. Trevathana niuea is compared with other species of Trevathana .

Iron and zinc content of hormosira banksii in New Zealand - R. R. M. Cooke; C. L. Hurd; J. M. Lord; B. M. Peake; J. A. Raven; T. A. V. Rees (New Zealand Journal of Marine and Freshwater Research, 2004)
In the Northern Hemisphere, brown seaweeds in the Order Fucales have been used extensively as bio‐monitors of heavy metal contamination in sea water, but in New Zealand there has been no assessment of the suitability of the Fucales in this role. We measured iron (Fe) and zinc (Zn) concentrations in the intertidal fucalean seaweed Hormosira banksii at three sites in Otago, southeastern New Zealand and two sites at Leigh, northeastern New Zealand. There was no evidence of Zn or Fe contamination at any site studied. Zn levels for H. banksii from Otago Harbour followed a trend similar to an earlier study of Ulva sp. and the Fe content reflected patterns previously observed in sea water. Thus, as for Northern Hemisphere fucalean seaweeds, H. banksii is potentially useful as a bio‐monitor for heavy metals in sea water. Levels of Fe and Zn were among the lowest of any brown seaweed worldwide, and the Fe content of H. banksii from Waterfall Reef, Goat Island Marine Reserve, Leigh, was 50% lower than samples from Otago. These low trace metal levels led us to examine if the growth of H. banksii in New Zealand is limited by Fe or Zn. The physiological requirements of Fe and Zn for growth were calculated and compared with measured values and we suggest that despite low Zn and Fe levels, these trace elements do not limit the growth of H. banksii .

First report of the Australian brown alga Dictyota furcellata (C. Agardh) Grev. from New Zealand - W. A. Nelson; K. F. Neill; J. A. Phillips (New Zealand Journal of Marine and Freshwater Research, 2004)
The Australian brown alga Dictyota furcellata (C. Agardh) Grev. is reported for the first time from New Zealand waters. It was found in a sheltered, shallow, subtidal site on the south‐western shores of Manukau Harbour, Auckland. Subsequent herbarium investigation revealed a further single collection made in 1938 from Charteris Bay, Lyttelton Harbour, Banks Peninsula. This species can be distinguished from all species of Dictyota previously reported from New Zealand by its very narrow, parallel‐sided axes (1 mm wide).

Analysis of quasi‐synoptic eddy observations in the New Zealand subantarctic - Michael J. M. Williams (New Zealand Journal of Marine and Freshwater Research, 2004)
In June 2001 a warm core eddy was observed simultaneously by satellite and shipboard measurements to the south of the Subtropical Front, at c. 50°S 172°W. The simultaneous acquisition of satellite altimeter data, together with shipboard velocity, and temperature and salinity observations has allowed a 3‐dimensional picture of this eddy to be developed. Analysis of the water mass composition showed it consisted of a mixture of between 45% and 70% Subtropical Water; the remainder being Subantarctic Water. The centre of the eddy was 1000 m deep. To find the radius of the eddy arankine vortex was fitted to the Acoustic Doppler Current Profiler velocity field, this gave a best fit of 65 km with a range from 30 to 80 km. For an eddy of this size the available potential energy was estimated at 2.4 × 10 13 J and the eddy's kinetic energy at 6.9 × 10 14 J.

Effects of deposit‐feeding bivalve (macomona liliana) density on intertidal sediment stability - S. D. Lelieveld; C. A. Pilditch; M. O. Green (New Zealand Journal of Marine and Freshwater Research, 2004)
Effects of macrofaunal feeding and bioturbation on intertidal sediment stability ( u * crit ) were investigated by manipulating density (0–3 × ambient) of the facultative deposit‐feeding wedge shell (Macomona liliana) on the Tuapiro sandflat in Tauranga Harbour, New Zealand. Sediment stability increased up to 200% with decreasing M. liliana density and this was correlated with greater sediment microalgal biomass and mucilage content. The change in stability occurred despite homogeneity of grain size amongst experimental treatments, highlighting the importance of macrofaunal‐microbial relationships in determining estuarine sediment erodibility.

Taxonomy of some halisarcida and homosclerophorida (Porifera: Demospongiae) from the indo‐pacific - Patricia R. Bergquist; Michelle Kelly (New Zealand Journal of Marine and Freshwater Research, 2004)
Several sponges with a thin encrusting form and of fragile construction have been collected in the Indo‐Pacific, and have proved difficult to differentiate, let alone identify, without recourse to electron microscopy. Here we re‐describe Halisarca melana de Laubenfels, 1954 from Palau, and H. metabola de Laubenfels, 1954 from Majuro Atoll in the Marshall Islands from new material, emphasising field characters such as coloration in life, surface features, and histological details accessible by light microscopy. Using similar characters two new species of Halisarca, H.ferreus sp. nov., from Zanzibar, Tanzania, and H . cerebrum sp. nov., from Palau, are recognised and described. Another genus belonging to a different subclass of Demospongiae also has fragile construction and encrusting growth form; this is Oscarella , and two new species of this genus are also described, O. stillans sp. nov. from the Philippines, and O. nigraviolacea sp. nov., from Pemba Island, Tanzania.

Seasonal profiles in growth, energy reserves, gonad development, and plasma steroids in age 1+ cultured Chinook salmon (Oncorhynchus tshawytscha) females - M. J. Unwin; C. W. Poortenaar; D. K. Rowe; N. C. Boustead; M. J. R. Porter (New Zealand Journal of Marine and Freshwater Research, 2004)
Sexual maturation in 2‐year‐old female Chinook salmon (Oncorhynchus tshawytscha) is unknown within their native range, but occurs in up to 20% of farmed stocks in New Zealand. To characterise the seasonal timing of oogenesis and subsequent ovarian development, we measured levels of plasma 17β‐estradiol and testosterone, condition factor, and gonadosomatic and hepatosomatic index, for freshwater‐reared female Chinook at 2–4‐week intervals during their second year of life (May 2001‐April 2002). These comprised two treatment groups under additional 24 h illumination from September to January, and two ambient controls. Macroscopic ovarian development first occurred in mid September (8 months before spawning), coinciding with detectable increases (≥0.3 ng ml ‐1 ) in both plasma steroids. Vitellogenesis was first observed in November and coincided with an increase in hepatosomatic index, possibly indicating the liver's role in transferring lipids to the developing ova. Neither mean weight nor the percentage of maturating fish (mean 6.9%) differed between the treatment and control groups at the end of the experiment, but ovarian development in the treatment group was advanced by 13 days relative to the controls. Reduced dark phase plasma melatonin levels confirmed that the additional light was sufficiently intense to produce a physiological response in the artificially illuminated fish.

Systema Porifera: a guide to the classification of sponges. Edited by John N. A.Hooper and Rob W. M.vanSoest. Published in 2002 by Kluwer Academic/Plenum Publishers, Dordrecht, The Netherlands (http://www.wkap.nl). Hardbound set of two volumes, 1810 p. ISBN: 0–306–47260–0. Price: €625.00, £431.00, US$688.00 (email: kluwer@wkap.com (Americas); services@wkap.nl (elsewhere)). - Patricia R. Bergquist; Michelle Kelly (New Zealand Journal of Marine and Freshwater Research, 2004)

Three new species of Neomenia (Mollusca: Solenogastres) from the Southern Hemisphere - Luitfried V. Salvini‐Plawen; Irene Paar‐Gausch (New Zealand Journal of Marine and Freshwater Research, 2004)
Archaeomenia prisca Thiele is re‐examined and three Neomenia species new to science (class Solenogastres, order Neomeniamorpha) are described and defined. One species, N. naevata spec, nov., comes from New Zealand waters and two species, N. megatrapezata spec. nov. and N. trivialis spec. nov., are recorded from one sample close to the South Shetland Islands. N. naevata possesses a sub‐vaginal, thin‐walled epithelial gland as do several other Neomenia species. N. megatrapezata as well as N. trivialis exhibit sac‐like elongations of the terminal midgut surrounding the copulatory stylet sheaths, similar to those of A. prisca . The biogeographic implications are considered.

Protocols for citing the authority for zoological names - R. M. McDowall; Sandra Stanislawek (New Zealand Journal of Marine and Freshwater Research, 2004)

Circulation within the Wairarapa Eddy, New Zealand - Stephen M. Chiswell (New Zealand Journal of Marine and Freshwater Research, 2003)
The Wairarapa Eddy appears as a permanent anticyclonic eddy situated off the east coast of the North Island, New Zealand. In April 2001 a spatial survey of the eddy was made on a ship equipped with an Acoustic Doppler Current Profiler (ADCP). The absolute circulation at 100 m was estimated by objective mapping of the ADCP‐derived velocities to produce a velocity field that has enforced non‐divergence. Assuming that enforcing non‐divergence produces the best estimate of the geostrophic flow, this velocity field can be used as a “level of known motion” to reference geostrophic velocities at other depths. In particular, it can be used to estimate the velocity at 2000 dbar, which is otherwise used in this region as a level of no motion. The resulting flow at 2000 dbar has a mean speed of 0.07 m s ‐1 , and appears to be well correlated with the surface flow.

Relationships between drifting and benthic invertebrates in three New Zealand rivers: Implications for drift‐feeding fish - Karen A. Shearer; John D. Stark; John W. Hayes; Roger G. Young (New Zealand Journal of Marine and Freshwater Research, 2003)
We assessed whether taxonomic structure and density of aquatic drift could be predicted from the benthos in three New Zealand rivers. The three main orders contributing to both the benthos and drift were Ephemeroptera, Diptera, and Trichoptera. Drift and benthic densities for all taxa and all rivers combined were not significantly correlated (adults inclusive and exclusive). There were significant positive correlations between benthic and drift densities for the three main drifting orders—Ephemeroptera, Diptera, and Trichoptera when data from all rivers were combined. However, these relationships were not always detected in individual rivers. The propensity for Deleatidium to drift was negatively related to chlorophyll a concentration; suggesting density‐dependent drift mediated by food limitation. Drift was reduced when periphyton chlorophyll a concentration was high in relation to benthic Deleatidium density. This highlights an unexpected effect of periphyton proliferation on invertebrate drift and drift‐feeding fishes. Despite finding some correlations between benthic and drifting communities, defining general relationships between benthic and drifting communities is challenging given the complexity of density‐dependent and density‐independent mechanisms that influence invertebrate drift.

Marine fisheries enhancement in New Zealand: Our perspective - John D. Booth; Owen Cox (New Zealand Journal of Marine and Freshwater Research, 2003)
Increasing human population and its demand for fishery products is placing mounting pressure on the coastal marine environment. As wild fisheries reduce in size or stabilise there is growing interest in enhancement as a means of restoring or increasing production. The purpose of this paper is to document marine enhancement initiatives in New Zealand and to describe species, or groups of species, of potential enhancement interest over the next 10 years. An overview of any potentially negative impacts of such enhancements is given. The rise in interest in fisheries enhancement in New Zealand in recent years, which is likely to further increase in coming years, flows from the successful Nelson scallop enhancement programme, encouraging results from other initiatives, and the growing momentum of marine enhancement internationally. However, there is also an increasing awareness that stocking alone is seldom enough, and that successful enhancement often requires restoration of key components of the marine environment itself. The species likely to be of most interest for enhancement in New Zealand over the next 10 years are scallops, dredge oysters, estuarine shellfish including cockles and pipi, toheroa, paua, rock lobster, certain seaweeds, snapper, and salmon. There will probably also be interest in the wider use of artificial reefs for ecosystem development. Such initiatives could potentially take place the length and breadth of the country, to the benefit (or cost) of all users, commercial, recreational, and customary. They will bring new challenges to managers of marine resources as demands for more localised management intensify.

Morphogenesis during sexual and asexual reproduction in Amphipolydora vestalis (Polychaeta: Spionidae) - Glenys D. Gibson; Ian G. Paterson (New Zealand Journal of Marine and Freshwater Research, 2003)
Both sexual and asexual reproduction occur in Amphipolydora vestalis , a small, sponge‐dwelling spionid polychaete. Sexual reproduction occurs through adelphophagy, where offspring are provided with extra‐embryonic yolk in the form of nurse eggs. Ingestion of nurse eggs sustains development until offspring hatch at late larval and early juvenile stages (22 days). Hatched young have an advanced morphology and alternatively crawl and swim, suggesting that a dispersive phase is brief or absent. Asexual reproduction occurs through architomy, in which a parent fragments into 4–6 pieces and each regenerates a complete body plan within 8 days. Asexual propagules remain within the parental tube until growth and differentiation are almost complete. Both reproductive modes were found at the same time in the same population, and asexual fragments often had well developed gametes in the coelom. Both reproductive modes facilitate local recruitment and a reduced dispersal potential. This is the first description of development within the genus Amphipolydora . Aspects of morphogenesis during asexual reproduction suggest that Amphipolydora is closely related to Polydorella , and that architomy in the Spionidae evolved from a widespread ability to regenerate, while paratomy is secondarily derived.

Sightings of mobulid rays from northern New Zealand, with confirmation of the occurrence of Manta birostris in New Zealand waters - C. A. J. Duffy; D. Abbott (New Zealand Journal of Marine and Freshwater Research, 2003)
Data from 31 sightings of mobulid rays from New Zealand are summarised. Mobulid rays are common to locally abundant off north‐east North Island, New Zealand during summer and early autumn. Collection records and sightings data indicate the spine‐tailed devil ray ( Mobula japanica ) is the most abundant mobulid in New Zealand waters. Photographic and video evidence confirming the occurrence of the manta ray ( Manta birostris ) in New Zealand waters is presented. Estimated disc widths for New Zealand M. birostris ranged from 200 to 790 cm. Unlike in tropical regions, mobulid rays are largely confined to the epipelagic zone off New Zealand.

A new species of Amphipolydora (Polychaeta: Spionidae) from New Zealand - IAN G. Paterson; Glenys D. Gibson (New Zealand Journal of Marine and Freshwater Research, 2003)
The species, Amphipolydora vestalis sp. nov. is described from northern New Zealand. A. vestalis is the second species described for the genus. A. vestalis is a sponge borer, inhabiting blind‐ending mud tubes within the sponge, Callyspongia cf. ramosa . Numerous individuals (tens to hundreds) were found in all C . cf. ramosa specimens examined, along with low numbers of the sponge borer Boccardia androgyna . Sexually reproductive individuals and egg strings containing embryos and nurse eggs (i.e., adelphophagy) were found concurrent with asexual individuals that reproduced by architomy.

Development of standard protocols for macroinvertebrate assessment of soft‐bottomed streams in New Zealand - John R. Maxted; Brent F. Evans; Mike R. Scarsbrook (New Zealand Journal of Marine and Freshwater Research, 2003)
Macroinvertebrate communities in hard‐bottomed (HB) and soft‐bottomed (SB) streams were compared to address questions on sample substrata, sample area, and data interpretation. Communities at HB and SB reference sites (native bush catchments) were distinctly different. SB reference sites had 50% of the total taxa, 33% of the Ephemeroptera, Plecoptera, and Trichoptera (EPT) taxa, and significantly lower Macroinvertebrate Community Index (MCI) and Semi‐Quantitative MCI (SQMCI) scores than HB reference sites. Ten EPT genera were abundant (>20 individuals per sample) at HB reference sites compared with one EPT genus ( Zephlebia ) at SB reference sites. The densities of macroinvertebrates at SB reference sites were

Thermal constraints on glycolytic metabolism in the New Zealand abalone, Haliotis iris: the role of tauropine dehydrogenase - Anthony J. R. Hickey; Rufus M. G. Wells (New Zealand Journal of Marine and Freshwater Research, 2003)
Black‐foot abalone, Haliotis iris , were sampled from two populations in warm northern waters, and from two in colder southern waters. Abalone muscle is characterised by high activity of the glycolytic pyruvate reductase enzyme, tauropine dehydrogenase (TDH). Adductor muscle TDH was profiled for thermostability and activity to test the hypothesis that the enzyme may show adaptation in titre or kinetic characteristics reflecting thermal habitat. Temperature dependency of the apparent Michaelis‐Menten constant of TDH for pyruvate ( app Km pyr ) suggested eurythermal enzyme behaviour below 20°C, and compromised function at the higher temperatures of northern populations occurring in the summer months. Thermostability profiles and enzyme activities suggest TDH expression does not differ significantly among populations ( P > 0.05), indicating that this locus shows no compensation for temperature. The optimal temperature for efficient TDH function, estimated from V max ./ app Km pyr , is close to 20°C. The possible thermal constraints on glycolytic metabolism in H. iris are discussed.

Some pathological abnormalities of New Zealand fishes - B. K. Diggles (New Zealand Journal of Marine and Freshwater Research, 2003)
A number of pathological abnormalities previously unrecorded in New Zealand fishes are described. A silver trevally ( Pseudocaranx dentex ) captured from the Bay of Islands exhibited swim bladder ectasia. Black oreo ( Allocyttus niger ) and smooth oreo ( Pseudocyttus maculatus ) had cysts of unknown aetiology (CUEs) in the gills at prevalences up to 76% and 81%, respectively, in some fishing areas. The CUEs appear long lived and may have some utility for stock discrimination. A hoki ( Macruronus novaezelandiae ) with X‐cell pseudotumours in the gill was recorded from the Chatham Rise. Alfonsino ( Beryx splendens ) had conspicuous Kudoa sp. cysts in the gills at prevalences of up to 28%. Smelt ( Retropinna retropinna ) from the Waikato River were infected with a xenoma forming, Glugea‐like microsporidian.

Development of a biotic index using the correlation of protozoan communities with chemical water quality - Jian‐Guo Jiang; Yun‐Fen Shen (New Zealand Journal of Marine and Freshwater Research, 2003)
A method of comparing data on protozoan communities with chemical parameters is presented. Using data from an extensive survey of the River Hanjiang in China, each species of protozoa has been given a species pollution value (SPV) related to its occurrence in waters with different degrees of pollution. A comprehensive chemical index is calculated for each site based on water quality standards for eight chemical parameters. The index is calculated from the relationship between the observed levels of each chemical at a site compared with the limits of the drinking water quality standards of the People's Republic of China. From the distribution of each species at sites with differing chemical index values, a SPV is calculated. The SPV for each species is obtained by summing the logarithmic value of 10 times the chemical pollution divided by the number of chemical parameters, then divided by the stations where the species occurs. The community pollution value (CPV), which is the average SPVs of all protozoa at a site, is used to evaluate water quality. The CPV has been shown to have a close correlation with the degree of water pollution. It is not necessary for all the protozoa in a sample to have SPVs listed in this paper, provided at least 56% of the protozoa in a sample have an SPV value, the CPV will be applicable.

Environmental controls on iron‐oxidising, sulfur‐oxidising and sulfate‐reducing bacteria in mine wastes, New Zealand - Debra A. Chappell; Dave Craw (New Zealand Journal of Marine and Freshwater Research, 2003)
Historic and modern tailings piles and waste dumps in east Otago (South Island) and the Coromandel Peninsula (North Island) of New Zealand encompass a wide range of physico‐chemical environmental conditions, and host chemolitho(auto)trophs (iron‐ and sulfur‐oxidising bacteria, IOB and SOB respectively) and sulfate‐reducing bacteria (SRB). Sulfide mineral grains are only marginally altered, even after up to 100 years of surficial exposure, at all sites examined. The environmental parameters of the tailings piles and waste rock dumps were examined to determine their effect on the growth of these bacterial isolates. This study revealed the co‐occurrence (at the cm scale) of IOB, SOB, and SRB in many of these environments, supporting previous findings from acidic sites and extending the spectrum to circumneutral‐to‐alkaline anoxic spoils. The apparently unweathered appearance of sulfide grains supports the idea that sulfate reduction dominates over sulfur oxidation in these environments. Temperature, rainfall, and dissolved metal(loid) concentrations appear to have little effect on the bacterial populations. These results indicate that the environmental parameters investigated have very little bearing on the presence of IOB, SOB, and SRB in the tailings piles and waste rock dumps examined in this study.

Recent occurrence of Cylindrospermopsis raciborskii in Waikato lakes of New Zealand - E. F. Ryan; D. P. Hamilton; G. E. Barnes (New Zealand Journal of Marine and Freshwater Research, 2003)
Cylindrospermopsis raciborskii is a toxin‐producing species of cyanobacteria that in autumn 2003 was recorded for the first time in three shallow (max. depth ≤5 m) Waikato lakes and a hydro‐electric dam on the Waikato River, New Zealand. It formed water blooms at densities >100 000 cells/ml in Lakes Waahi and Whangape. Net rates of population growth >0.2 day –1 were recorded for C. raciborskii in Lakes Ngaroto, Waahi, and Karapiro, based on comparisons of low numbers (detection of 15 000 cells/ml) in the subsequent sample “x”‐“y” days later. C. raciborskii may be well adapted to rapid proliferation in the Waikato lakes, which are eutrophic to hypertrophic, with high light attenuation, and where nitrogen (N) fixation may provide it with a competitive advantage over non‐nitrogen fixing algae under N‐limited conditions.

Egg cannibalism by inanga ( Galaxias maculatus ) - Richard Allibone (New Zealand Journal of Marine and Freshwater Research, 2003)
Egg cannibalism by inanga ( Galaxias maculatus ) was found to occur immediately after spawning. Spent and immature inanga from a school of 335 fish consumed between 0 and 51 eggs each. As inanga spawning sites are high on the river bank and only accessible on high spring tides, further opportunities for egg predation are limited to when the eggs are re‐submerged at hatching on the next suitable spring tides. It is unclear whether the cannibalism observed represents a reduction in short‐term reproductive fitness without providing long‐term gains.

DNA and morphological identification of an invasive swimming crab, Charybdis japonica , in New Zealand waters - P. J. Smith; W. R. Webber; S. M. McVeagh; G. J. Inglis; N. Gust (New Zealand Journal of Marine and Freshwater Research, 2003)
Mitochondrial DNA sequences were used to identify an invasive swimming crab found in Waitemata Harbour, New Zealand. A 457 base sequence of the cytochrome oxidase 1 gene was compared in New Zealand specimens and nine species of Charybdis from Australia and Asia. The New Zealand specimens aligned with C. japonica . The diagnostic morphological characters of C. japonica were also checked in 54 specimens of the species collected in Waitemata Harbour, and concur with the mtDNA result. This is the first record of C. japonica establishing populations outside its native range. C. japonica , along with C. hellerii and the Lessepsian migrant C. longicollis , are the only known invasive species of Charybdis. C. japonica and C. hellerii are two of the few Charybdis species that inhabit the intertidal zone, and it is likely that the intertidal characteristics of these species contribute to their success as invasive species.

First identification of the cylindrospermopsin‐producing cyanobacterium Cylindrospermopsis raciborskii in New Zealand - S. A. Wood; D. J. Stirling (New Zealand Journal of Marine and Freshwater Research, 2003)
Cylindrospermopsis raciborskii is a planktonic freshwater cyanobacterium that is becoming increasingly prevalent in water bodies worldwide. During a survey of toxic cyanobacteria in New Zealand, C. raciborskii was identified in a sample collected from Lake Waahi (Waikato). This is the first identification of this species in New Zealand. Liquid chromatography‐mass spectrometry and liquid chromatography‐tandem mass spectrometry were used to confirm the presence of the cyanotoxins cylindrospermopsin (CYN) and deoxy‐cylindrospermopsin (do‐CYN). Detection of CYN and do‐CYN demonstrates that C. raciborskii is a now a species of concern in recreational, stock drinking, and potable water supplies in New Zealand.

The Southland Current: A subantarctic current - Philip J. H. Sutton (New Zealand Journal of Marine and Freshwater Research, 2003)
The Southland Current is a northward flow of water along the south‐east coast of New Zealand. This current has been studied many times since the early 1960s, with particular emphasis on an associated narrow coastal band of warm, salty water of subtropical origin, separated from offshore cold, fresh Subantarctic Water (SAW) by the Southland Front. Previous works on the Southland Current state that it advects modified warm, salty Subtropical Water (STW). This work quantifies the relative proportions of SAW and STW within the current. The Southland Current has a mean transport of 8.3 Sv comprising c. 90% SAW and 10% STW. The mean properties advected result from the current extending offshore of the Southland Front: in fact the core of the current is offshore of the Southland Front.

Spawning site selection, egg development, and larval drift of Galaxias postvectis and G. fasciatus in a New Zealand stream - Sjaan C. Charteris; Richard M. Allibone; Russell G. Death (New Zealand Journal of Marine and Freshwater Research, 2003)
Twelve Galaxias postvectis (shortjaw kokopu) and four G. fasciatus (banded kokopu) spawning sites were found on the margins of the Katikara Stream, Taranaki, New Zealand. This is the first time G. postvectis spawning sites have been documented. G. fasciatus spawning sites discovered in this study confirm previous observations elsewhere in New Zealand. These spawning sites were all found out of water, variable distances from the base flow water level amongst stony substrate, vegetation, and debris. Most G. fasciatus appeared to lay their eggs, and subsequently hatch, c. 3 weeks earlier than G. postvectis , which spawned from 9 to 17 May 2001. G. brevipinnis (koaro) larvae were also identified drifting downstream in late May and mid June 2001. Deposition of eggs and subsequent hatching were found to be associated with elevated flows.

Non‐destructive video image analysis method for measuring growth in sponge farming: Preliminary results from the New Zealand bath‐sponge Spongia ( Heterofibria ) manipulatus - Sean Handley; Shane Kelly; Michelle Kelly (New Zealand Journal of Marine and Freshwater Research, 2003)
The skeleton of the New Zealand endemic sponge Spongia ( Heterofibria ) manipulatus (Demospongiae: Dictyoceratida: Spongiidae) has physical qualities that make it suitable for use as a bath‐sponge. The species is particularly abundant around exposed coastlines of D'Urville Island in the Marlborough Sounds and on the east coasts of Northland and Coromandel Peninsula. Growth rates and changes in the shape of explants of S . ( H .) manipulatus were monitored for a period of 12 months on a pilot marine farm near D'Urville Island, using digital video image analysis. This nondestructive method proved to be an accurate means of monitoring sponges for changes in size when compared with repeated wet‐weighing ex situ . Sponge explants increased in size by an average of 28.5% from September 2000 to June 2001, after which growth varied markedly to September 2001, with most of the explants changing little or shrinking in size. Implications of the biological and physical characteristics of S . ( H .) manipulatus , for the future commercial production of this species, are discussed.

Effect of Pinus radiata logging on stream invertebrate communities in Hawke's Bay, New Zealand - Russell G. Death; Brenda Baillie; Pieter Fransen (New Zealand Journal of Marine and Freshwater Research, 2003)
Invertebrate communities and associated environmental characteristics were monitored at three Pinus radiata and three pasture stream sites in the Pakuratahi and Tamingimingi Stream catchments, New Zealand, respectively, at nine irregular intervals between December 1996 and April 2001. The Pakuratahi sites were logged between May 1998 and September 1999. Following logging the Pakuratahi Stream invertebrate communities changed from being dominated by a diversity of mayfly species to communities dominated by a high abundance of Chironomidae, Aoteapsyche sp., Elmidae, Ostra‐coda, and Potamopygrus antipodarum . Invertebrate communities that developed following the pine forest harvesting closely resembled those at pasture stream sites in the adjoining Tamingimingi catchment. Invertebrate communities at the pasture stream sites were dominated throughout the study by the same taxa as in the post‐harvest pine sites, except immediately following a storm in July 1997 when mayflies became proportionally more abundant. Biotic indices of water quality, such as the Macroinvertebrate Community Index and Quantitative Macroinvertebrate Community Index, reflected the change in invertebrate communities at the Pakuratahi sites after harvesting, shifting from impact “sensitive” taxa to more “tolerant” taxa. In April 2001 (1.5–2.5 years after harvesting) invertebrate communities had not recovered to their pre‐harvest structure. Recovery of invertebrate communities from a natural disturbance, a major storm in July 1997, was much more rapid (5 months) than the recovery observed from forest harvesting, however. An increase in streambed fine sediment may have been primarily responsible for the changes to invertebrate communities following forest harvesting.

Population viability analysis for Hector's dolphin ( Cephalorhynchus hectori) : A stochastic population model for local populations - Stephanie M. Burkhart; Elisabeth Slooten (New Zealand Journal of Marine and Freshwater Research, 2003)
Mortality of Hector's dolphin (Cephalorhynchus hectori) in gill‐net fisheries is a threat to local populations throughout its range. This population viability analysis extends previous work by exploring a wider range of fishing levels and population growth rates, by incorporating year‐to‐year and environmental variability and by reporting results for smaller population units. Ten of the 16 populations are likely to continue to decline, five are indefinite, and one is likely to increase. All populations subjected to high fishing effort are declining. The only population predicted to increase is partly protected by a marine mammal sanctuary (created in 1988) which reduces the amount of gill‐net fishing. Conservation measures are most urgently needed for the highly threatened North Island population, in particular the dolphins at the northern and southern end of this range.

Tuna schools/aggregations in surface longline data 1993–98 - David S. Kirby; Edward R. Abraham; Michael J. Uddstrom; Hudson Dean (New Zealand Journal of Marine and Freshwater Research, 2003)
Exploratory data analysis of a high‐resolution (hook‐by‐hook), 6‐year time series (1993–98) of observed longline catch data for tunas was used to investigate fine‐scale spatial patterns along individual sets that may be indicative of social behaviour (i.e., schooling) and/or the response of individual fish to favourable extrinsic conditions (i.e., aggregation). Methods of spatial data analysis (i.e., nearest neighbour analysis) that have previously been applied in various other sciences (e.g., forestry and astronomy) were used. Results indicate strong clustering of individual tunas at characteristic scales within the set. Mean Nearest Neighbour Distances (NNDs) were between 100 and 200 m, compared with NNDs of 200–700 m predicted by a heterogeneous Poisson process on the same spatial domain. The results suggest that these adult tunas were either schooling or aggregating at the time of capture; this may therefore be related either to social behaviour or to sub‐mesoscale oceanographic features. An aggregation index was derived from the NNDs, giving a classification method that may be used for similar data and the development of empirical models attempting to relate patterns in fish catch distributions to environmental variables. The success of such models will ultimately depend on elucidating the ecological processes reflected in oceanographic features at biologically meaningful spatial scales.

Use of in‐stream cover types by adult banded kokopu ( Galaxias fasciatus ) in first‐order North Island, New Zealand, streams - David K. Rowe; Joshua Smith (New Zealand Journal of Marine and Freshwater Research, 2003)
The relative importance of wood material in providing in‐stream cover for adult banded kokopu ( Galaxias fasciatus ) was determined in first‐order, North Island, New Zealand, streams. Three groups of streams, each differing in the relative amount of three types of in‐stream cover (i.e., wood, boulders, undercut banks) were selected and banded kokopu were sampled in their pools using electric fishing. Banded kokopu occurred beneath boulders, undercut banks, and wood material in all pools except those lacking any in‐stream cover, or those where large (total length >400 mm) eels were present. Their presence in pools was therefore highly dependent on in‐stream cover, provided large eels were absent. In streams where the cover provided by boulders was lacking, banded kokopu selected mainly undercut banks and wood. However, in streams containing large amounts of bank and boulder cover, wood was under‐utilised, indicating that it was least preferred. In pools providing a choice of cover types, bank cover was more frequently used than other types, indicating that it is preferred. The mean size of banded kokopu in pools was positively related to their relative abundance, and their abundance was in turn related to habitat quality as defined by in‐stream cover. Streams with the least amount of bank cover had the lowest number of pools occupied by banded kokopu, fewer banded kokopu per pool, fewer pools containing two or more banded kokopu, and the smallest banded kokopu. Collectively, these data indicate that bank cover in pools provides optimal habitat for banded kokopu, and that wood material was important only where other types of more permanent cover were lacking. Logs and wood slash from logging operations could therefore be important for increasing banded kokopu habitat in logged streams where bank and boulder cover are scarce.

Comparison of portable nephelometric turbidimeters on natural waters and effluents - Paul J. Barter; Toni Deas (New Zealand Journal of Marine and Freshwater Research, 2003)
Five different cuvette‐style portable turbidimeters using a nephelometric (side scattering of light) principle were assessed simultaneously to determine between‐meter variability. The assessment was conducted using primary formazin standards, and a variety of different effluent types and receiving waters encompassing a wide range of turbidities and optical properties. For the formazin standards, the coefficient of variation (CV) ranged from 1.5% to 6.8% providing an indication of precision. For the effluents and receiving waters, the CV ranged from 6.6% to 44.1%, which compares favourably with previous interlaboratory studies reporting CVs ranging from 23% to 144%; however, the previous studies were not direct side‐by‐side comparisons of meters. A power analysis showed that, with the exception of very clear headwater streams, single turbidity samples are sufficient to detect changes in clarity recommended in the New Zealand guidelines for the management of water colour and clarity.

South Pacific reef plants. A divers’ guide to the plant life of South Pacific coral reefs. By Diane ScullionLittler and Mark MastertonLittler. Published in February 2003 by OffShore Graphics Inc., Washington, D.C., United States. 331 p. ISBN: 0–9678901–9‐5. Price: US$45.00. - G. Robin South (New Zealand Journal of Marine and Freshwater Research, 2003)

Distribution of macroinvertebrate assemblages in the Azul‐Quemquemtreu river basin, Patagonia, Argentina - M. Laura Miserendino; Lino A. Pizzolon (New Zealand Journal of Marine and Freshwater Research, 2003)
Longitudinal and seasonal changes in physical and chemical variables, and macro‐invertebrate community structure‐function were examined in the Azul‐Quemquemtreu river system in the subantarctic forest of Patagonia, Argentina. Patagonian mountain streams have a marked seasonal discharge pattern and may have high suspended sediment loads because of forestry and other land‐use practices. The main physical differences among sites were in substrate size (boulder‐pebble/ sand), mean width (3–37 m), discharge ( 3 s –1 ), total alkalinity (275–1210 meq litre –1 ) and conductivity (31–137 #GMS cm –1 ). Species richness and Ephemeroptera, Plecoptera, and Trichoptera richness decreased from upstream sites to the mouth of the river system and were affected by land use. Macroinvertebrate assemblages were influenced by physical (substrate size, width, discharge, current velocity) and chemical (alkalinity and conductivity) variables, and mean density of macroinvertebrates was significantly higher at the Quemquemtreu sites than the Azul sites. Canonical Correspondence Analysis indicated that seasonal trends in macroinvertebrate community composition were related to changes in environmental characteristics of the river, especially water temperature and discharge. The composition of benthic communities in rivers of the Patagonian Andes largely reflect characteristics related to stream size, but factors at the reach scale best explain variation in abundance data. Collector‐gatherers were the dominant functional feeding group at all sites. Faunas have similarities with those of New Zealand in taxonomic‐functional composition, with a predominance of Chironomidae (Diptera), Leptophlebiidae (Ephemeroptera), and Gripopterygidae (Plecoptera).

Wave hindcast for the New Zealand region: Deep‐water wave climate - Richard M. Gorman; Karin R. Bryan; Andrew K. Laing (New Zealand Journal of Marine and Freshwater Research, 2003)
The wave evolution model WAM (WAve Model) has been implemented for the New Zealand region and used to simulate the generation and propagation of deep‐water waves over a 20‐year period (1979–98). The model extends to include the relevant generation areas of the south‐west Pacific and Southern Oceans. Input winds for the model were derived from the European Centre for Medium‐Range Weather Forecasts (ECMWF). The resulting synthetic wave climatology will provide a valuable tool for researchers and coastal planners, as it will help fill gaps in the available wave information for New Zealand waters. In this paper the hindcasts are described, and comparisons are made with wave height data from the altimeters flown on the TOPEX/ Poseidon and ERS1 and ERS2 satellite missions. Long‐term mean significant wave heights from the hindcast were generally 0.3–0.5 m lower than values from “buoy‐equivalent” altimeter data throughout the comparison region (150°E‐170°W, 60°S‐20°S). Hindcast distributions of significant wave height occurrence matched satellite data at the lowest wave heights and above the peaks of the distributions, but tended to overestimate occurrence below the peak and underestimate the occurrence of the largest wave events. The hindcast was then used to characterise the wave climate of the New Zealand region. Some prominent features noted were the large mean heights (3.6 m) in the high latitudes of the Southern Ocean, associated with strong prevailing westerlies. North of this band, waves largely propagate towards the north‐east, with diminishing mean heights, further attenuated by the blocking effect of the New Zealand landmasses. This results in mean wave heights of c. 2 m in offshore waters north‐east of New Zealand. Annual cycles of mean wave height with a range of c. 1 m were identified throughout the region. These were found to have minima in summer (December/January), and either unimodal maxima in winter (June/July) for tropical and temperate latitudes, or bimodal maxima (May and August) in southern waters. Longer‐term variations were also noted in the form of correlations with the El Niño/Southern Oscillation. Positive correlations ( R +0.2) were found off the north‐east coast of the North Island, indicating a moderate tendency for increased wave heights there during La Niña conditions, whereas negative correlations were found south and south‐west of New Zealand ( R ‐ 0.2), and in the Fiji/Vanuatu region ( R +0.4), reflecting wave height enhancements in the El Niño phase.

Population structure, individual movement, and growth rate of shortjaw kokopu ( Galaxias postvectis ) in two North Island, New Zealand streams - Richard Allibone; Dean Caskey; Rosemary Miller (New Zealand Journal of Marine and Freshwater Research, 2003)
The shortjaw kokopu ( Galaxias postvectis ), although widely distributed throughout New Zealand, is only known from a few sites and generally with extremely low population numbers. Two sites in Taranaki (Katikara Stream and Stony River tributary) were found to contain relatively high densities of shortjaw kokopu. These sites were monitored at 6‐monthly intervals over 3½ years to gather site fidelity and growth rate data. Half‐way through the sampling period the riparian vegetation alongside the Katikara Stream site was destroyed. Although this was unfortunate, it allowed examination of the impact of a disturbance event of this nature on shortjaw kokopu growth and behaviour. The density of shortjaw kokopu in Katikara Stream was about twice that in the Stony River tributary, whose population was characterised by fewer but larger individuals. Growth rate was significantly greater for smaller fish, and varied between the two sites. Fish in the Katikara Stream were generally site loyal with only a small percentage of mobile fish; however, greater movement from sites was noted immediately after the disturbance event.

Record of a wild intersexual rainbow trout ( Oncorhynchus mykiss ) in Taupo, New Zealand - Michel Dedual (New Zealand Journal of Marine and Freshwater Research, 2003)
For the first time in Taupo and in New Zealand an intersexual rainbow trout ( Oncorhynchus mykiss ) was identified. The fish was caught during the spawning migration by an angler fishing in the Tongariro River in June 2001. The external appearance of the fish had more male than female features. The fish had testes and ovaries distributed in a typical “lobular” form. The isolated nature of such occurrence of intersexual trout in Taupo and the high water quality in the catchment suggest that this phenomenon was most likely spontaneous rather than induced by environmental contamination.

Endemic new cyclostome bryozoans from Spirits Bay, a New Zealand marine‐biodiversity “hotspot” - Paul D. Taylor; Dennis P. Gordon (New Zealand Journal of Marine and Freshwater Research, 2003)
Two notable species of erect cyclostome bryozoans from a nearshore benthic fauna off Spirits Bay, northernmost New Zealand, are described here for the first time. The first, Spiritopora perplexa gen. et sp. nov., is an endemic cerioporine‐grade genus which is abundant in this area. Colonies are characterised by an unusual combination of fixed‐and free‐walled skeletal morphologies: autozooids forming the extensive encrusting colony bases are normally fixed‐walled, whereas those forming the short, bifoliate erect branches are usually free‐walled. The highly distinctive morphology of S. perplexa , very different from any other fossil or Recent cyclostome, together with its success in overgrowing competitors for space, makes its restricted geographical distribution puzzling and highlights the importance of conservation in this area now closed to trawling, Danish seining, and commercial scallop dredging. The second species, Calvetia osheai sp. nov., is less common, and has small, tree‐like colonies. It is the third species assigned to this distinctive cancellate genus, previously known only from Recent of Tierra del Fuego and the Eocene of Antarctica.

Wave hindcast for the New Zealand region: Nearshore validation and coastal wave climate - Richard M. Gorman; Karin R. Bryan; Andrew K. Laing (New Zealand Journal of Marine and Freshwater Research, 2003)
Historically, wave data coverage of New Zealand's coast has been poor, particularly for directional records. With very few data sets available of more than 1 year's duration, it has been difficult to establish accurate wave climatologies. To help fill in the gaps in our wave records, the wave generation model WAM (WAve Model) has been implemented over a domain covering the south‐west Pacific and Southern Oceans. The model has been used to hindcast the generation and propagation of deep‐water waves incident on the New Zealand coast over a 20‐year period (1979–98), using winds from the European Centre for Medium‐Range Weather Forecasts (ECMWF). The resulting synthetic climatology is expected to provide a valuable tool for researchers and coastal planners. The hindcasts were compared with data from wave buoy deployments at eight representative sites around the New Zealand coast. With appropriate interpolation and correction for the effects of limited fetch and sheltering by land, the hindcast was found to provide a satisfactory simulation of wave conditions at sites on exposed coasts. Regression between measured and hindcast significant heights at the four deep‐water sites (100–120 m) achieved scatter indices (ratio of root mean square error to mean) averaging 0.28. At the four shallower sites (30–45 m), the corresponding scatter index averaged 0.49, indicating that for regions of complex coastal topography, deep‐water spectra do not represent inshore conditions well. Wave spectra can be considerably modified by the processes of refraction and shoaling. To address these effects, nearshore wave transformations in the outer Hauraki Gulf were investigated using the shallow water model SWAN (Simulating WAves Nearshore), which was used to derive wave statistics at nearshore locations from deep‐water wave spectra obtained from the hindcast. The simulations were validated using data from an inshore site in 30 m water depth at Mangawhai on the north‐east coast of the North Island. Use of the nested model improved the agreement between model and measured significant wave height, decreasing the scatter index from 0.50 to 0.26. The suite of tools provided by the hindcast and localised, shallow water models can provide accurate new wave information for most of New Zealand's coastline.

Stock structure of bluenose ( Hyperoglyphe antarctica ) off the north‐east coast of New Zealand based on the results of a detachable hook tagging programme - Peter L. Horn (New Zealand Journal of Marine and Freshwater Research, 2003)
In late 1987, bluenose ( Hyperoglyphe antarctica ) were tagged with streamers attached to fish hooks, at six commercial fishing grounds between Gisborne and Cape Palliser, New Zealand. The tagged hooks were fished on commercial trot lines, but were attached with traces of 5.5 kg breaking strain nylon that broke when the fish took the hook and struggled to escape. Based on catches from full strength control lines fished simultaneously with the detachable gear, 1971 bluenose were tagged. In the subsequent 8.5 years, 44 tagged bluenose (where both the sites of tagging and recapture where known) were recaptured. All but seven of these returns occurred in the first year after tagging, indicating that the rate of long‐term tag retention was not good. Bluenose appeared to be relatively sedentary in the short term, but were capable of quite rapid and extensive movement. Four tagged fish had travelled distances in excess of 450 km, with movements to both the north and south of the tagging area. These data indicate that bluenose off the eastern coast of New Zealand between North Cape and Kaikoura probably comprise a single biological stock.

The “Wahine storm”: Evaluation of a numerical forecast of a severe wind and wave event for the New Zealand coast - Michael J. Revell; Richard M. Gorman (New Zealand Journal of Marine and Freshwater Research, 2003)
The “Wahine storm” was one of the two worst regenerating tropical cyclones to hit New Zealand last century. Ex‐tropical systems of this type are the major source of coastal hazards in the form of severe winds and waves in the New Zealand region. At the time, the likely weather associated with the storm was well forecast, although its expected path was not. Taking advantage of recently produced reanalysis data from the National Centres for Environmental Prediction (NCEP) and using the Regional Atmospheric Modelling System (RAMS) atmospheric model and WAve Model (WAM) wave model, we have simulated the atmospheric and wave conditions associated with the Wahine storm. Using modern computing methods, the path and storm intensity were quite well forecast although uncertainties in the initial positions of the low level tropical vortex and the upper level mid‐latitude trough lead to a 3‐h delay in the forecast arrival of the associated southerly change at Wellington. This illustrates the need for forecasters to realise the limitations of the tools they are using. The waves forecast around the coasts of New Zealand based on the winds from this atmospheric forecast were very good between North and East Cape and down the Canterbury coast, but the model failed to produce the 10–12 m seas experienced in Wellington at the time of the sinking of the TEV Wahine . The westward error in the storm track, though a relatively modest 50–100 km, is likely to have contributed to this under‐prediction. A comparison of 20 years of model hindcast waves round the New Zealand coasts with shorter periods of Waverider observations near Wellington indicated that the wave model at 1.125° resolution generally under‐predicts the full degree of variability of wave height seen during extreme wave events in the Wellington region. It is likely that limited spatial and temporal resolution of the wind and wave models is a limiting factor in this respect. It was found that significant improvement in the timing and heights of the forecast waves was achieved by interpolating between the 2.5° spatially resolved and 6‐h time resolved NCEP atmospheric data using a sophisticated weather prediction model. Provided the resolution of the winds driving the wave model was better than 1° and the frequency better than 1 h then large gains were made. Increasing the resolution to 0.333° increased the peak waves by a further metre but going to 0.1° made little difference except near sheltered coastal regions.

Effect of fall height and notch shape on the passage of inanga (Galaxias maculatus) and common bullies (Gobiomorphus cotidianus) over an experimental weir - Cindy F. Baker (New Zealand Journal of Marine and Freshwater Research, 2003)
The effect of fall height and notch shape on fish passage over an experimental weir was evaluated for two native diadromous fish species, the common bully (Gobiomorphus cotidianus) and adult and juvenile inanga (Galaxias maculatus) . Juvenile inanga and common bullies were restricted by falls of 10 cm or higher whereas adult inanga were not restricted until a fall height of 20 cm was reached. Notch shape had a significant effect on common bully passage, with fish negotiating the v‐notch weir more easily than the rectangular or circular weirs. There was no real effect of notch shape on adult inanga passage, although juvenile inanga were restricted by a wide rectangular weir. The size of common bullies and adult inanga affected their passage, with larger fish surpassing the weirs with greater ease than smaller fish. The length of juvenile inanga did not influence their ability to pass the weirs. Fall height, rather than notch shape was the greatest factor restricting passage of both species, although the amount of turbulence below the weir may be a factor influencing the ability of fish to negotiate weirs.

A temperate, tidal lake‐wetland complex 1. Water balance and ecological implications - Marc Schallenberg; Carolyn W. Burns; Barrie M. Peake (New Zealand Journal of Marine and Freshwater Research, 2003)
A water‐balance model was developed for a tidal lake‐wetland complex to: (1) determine the relative contribution of hydrological flows through the lake‐wetland complex; (2) determine the tidal and non‐tidal hydraulic residence times of two lakes in the lake‐wetland complex; and (3) estimate the potential importance of groundwater inputs to the lake‐wetland complex. All surface hydrological inputs to the system were either measured or estimated over 1 year. Daily evaporation from the water bodies was also estimated. Discharge at the outflow of the lake‐wetland complex was monitored to calculate the net daily outflow. A correction procedure was used to remove the error resulting from aliasing of the daily calculation period and the tidal period. The difference between the measured net outflow and that calculated by the water‐balance model indicated that a large amount of net discharge from the lake‐wetland complex may have been a result of previously unrecognised groundwater inputs to the system. The non‐tidal hydraulic residence times of the two lakes differed markedly as did the relative importance of tidal inflows. The influence of variation in tidal and non‐tidal hydraulic residence time on limnological processes is discussed, particularly with respect to impacts of global climate change on tidal lake ecosystems.

Historic deforestation and the fate of endemic invertebrate species in streams - Jon S. Harding (New Zealand Journal of Marine and Freshwater Research, 2003)
Deforestation is a global phenomenon threatening the biodiversity of many unique forested ecosystems. The volcanic calderas of Banks Peninsula, New Zealand, experienced widespread deforestation from 1860 to 1900 when >98% of the indigenous forest was removed. Streams on the Peninsula possess several regionally‐endemic species. The objective of this study was to assess the effect of historic deforestation on stream faunas by surveying the distribution of endemic and other benthic invertebrate species in relation to remnant and regenerating indigenous forest fragments. Twenty‐seven sites, in nine catchments were surveyed. Three catchments were dominated by forest, three by farmland, and three were predominantly farmland with forested headwaters. Taxonomic richness was significantly greater in forested streams than agricultural streams, particularly for Ephemeroptera, Plecoptera, and Trichoptera taxa. Distributions of the regionally‐endemic hydrobiosid caddisflies Costachorema peninsulae and Edpercivalia banksiensis were restricted to forest fragments. Two other endemics, the stonefly Zelandobius wardi and the caddisfly Hydrobiosis styx , were rarely collected but seemed to be restricted to headwater sites in forest. In contrast, the blepharicerid Neocurupira chiltoni was widely distributed in streams, regardless of land cover, and in relative abundances unrelated to site location within the catchment. Evidence from Banks Peninsula streams suggests that throughout New Zealand a number of species unknown to science may have been lost because of past deforestation, and that remnant forested habitats may be vital to the conservation and preservation of regionally endemic species.

Length‐mass models for some common New Zealand littoral‐benthic macroinvertebrates, with a note on within‐taxon variability in parameter values among published models - Rick J. Stoffels; Stefanie Karbe; Rachel A. Paterson (New Zealand Journal of Marine and Freshwater Research, 2003)
Regression models are developed and presented to predict dry mass (mg) from two linear dimensions (mm) for 17 benthic macroinvertebrate taxa common to littoral zones of New Zealand lakes. We also provide regression models to predict body length from head capsule width for the major insect taxa. Dry mass was best explained as a power function of all linear dimensions: M = a L b .Parameters are presented in the log 10 ‐transformed linear form of this power function. Body length was a simple linear function of head capsule width for all insect taxa, hence parameters for these models are presented as untransformed values. We also provide family level models for the Chironomidae, and compare our chironomid body length‐mass model with other published Chrionomidae length‐mass models. There was a very high degree of variability in parameter values among published length‐mass models for the family Chironomidae (mean coefficient of variation for mass at length = 148%). We discuss the potential causes and implications of this variability.

A temperate, tidal lake‐wetland complex 2. Water quality and implications for zooplankton community structure - Marc Schallenberg; Carolyn W. Burns (New Zealand Journal of Marine and Freshwater Research, 2003)
Lakes Waihola and Waipori are shallow, coastal, tidal lakes that experience wind‐induced sediment resuspension, saline intrusions, and high inputs of nutrients. To determine the influence of externally‐driven, physical factors on spatial and temporal patterns of water quality in the two lakes, meteorological, hydrological, and water quality data were collected over 1 year. Multivariate analyses indicated that wind energy was driving the main water quality gradient in the lakes, which was primarily related to wind‐induced resuspension of lake sediments. The major, seasonally regulated, non‐tidal freshwater inflow was important in determining nutrient and salinity gradients in the lakes. The main nutrient inputs to the system were identified as the regulated, non‐tidal inflow (the upper Waipori River) and the tidal inflow (lower Waipori River). The impact of water quality gradients on zooplankton community structure in the lakes was assessed by canonical multivariate methods. Salinity gradients, caused by seasonal saltwater intrusions, were strongly related to zooplankton community structure in the lakes. Nutrient gradients (indicative of trophic state) were also related to zooplankton community structure. Although wind‐induced sediment resuspension had the largest impact on water quality in the lakes, it had little impact on the zooplankton community structure in either lake. The relationships between water quality and zooplankton community structure were confounded in Lake Waipori because of its very short hydraulic residence time (annual mean =1.9 days). Zooplankton community structure was resilient to short‐term changes in suspended particulate matter concentrations but not to seasonal changes in salinity. The results of this study support others which have shown impacts of even relatively small variations in salinity on the structure of zooplankton communities. This highlights the vulnerability of zooplankton communities in coastal lakes and wetlands to increasing salinity resulting from sea level rise and global climate change.

Lack of genetic divergence found with microsatellite DNA markers in the tarakihi Nemadactylus macropterus - Christopher P. Burridge; Adam J. Smolenski (New Zealand Journal of Marine and Freshwater Research, 2003)
Three classes of molecular markers are commonly employed during population genetic studies of marine taxa: allozymes, mitochondrial DNA (mtDNA), and microsatellite DNA. These markers differ in their levels of polymorphism, and the ease and cost of their application. Nemadactylus macropterus is a commercially important marine fish from New Zealand and southern Australia that has been the subject of genetic (allozyme, mtDNA) and non‐genetic (otolith microchemistry, larval advection) studies of stock structure. We collected microsatellite DNA data from this species to compare the utility of these molecular markers with those genetic methods previously applied to N. macropterus . Microsatellites did not indicate significant divergence among Australian samples, or between Australian and New Zealand samples. The latter is incongruent with the allozyme and mtDNA studies, and it is suggested that allelic homoplasy has hindered the resolution of population structure when using microsatellites.

Non‐diadromous recruitment in coastal populations of common bully ( Gobiomorphus cotidianus) - Gerard P. Closs; Melvin Smith; Bernard Barry; Andreas Markwitz (New Zealand Journal of Marine and Freshwater Research, 2003)
Otolith microchemistry of common bullies (Gobiomorphus cotidianus) collected from the lower reaches of the Mataura, Clutha, and Taieri/Waipori River systems of New Zealand was examined using particle induced X‐ray emission (PIXE). High strontium:calcium (Sr:Ca) ratios in otolith cores relative to otolith edges suggested either diadromous or estuarine‐reared common bullies are present in all three systems, including fish collected from Clydevale (50 km inland) on the Clutha River. However, constant or slightly variable Sr:Ca ratios from otolith core to edge, suggesting a non‐diadromous life history, were also observed in fish from the lower Mataura and Taieri/Waipori systems, even where access to the sea was continuously available. The results suggest that diadromy in common bully may be facultative, and that a proportion of the common bully population may be non‐diadromous in river systems where suitable larval/juvenile rearing habitat is present.

River water quality trends and increased dairying in Southland, New Zealand - Keith D. Hamill; Graham B. McBride (New Zealand Journal of Marine and Freshwater Research, 2003)
Trends in six water quality variables measured at 29 Southland, New Zealand, freshwater sites between July 1995 and June 2001 have been assessed. These are compared to changes in livestock numbers to assess whether water quality changes could have been driven by the intensification and expansion of dairy farming and/or by other pressures. Trends were assessed for raw and for flow‐adjusted data, the latter being a better indicator of effects of changing external pressures on water quality (an observed water quality trend may be merely the result of changes in river flow). Results indicate that increased dairy farming has been associated with increasing concentrations of dissolved reactive phosphorus. There has been a worsening in other water quality variables (oxidised nitrogen, dissolved oxygen) but these also occurred in non‐dairying catchments. An improvement in observed water clarity disappeared after flow adjustment. Continued monthly water quality monitoring is necessary to watch for emerging trends.

Seasonal changes in macrophyte biomass in South Island lowland streams, New Zealand - Tenna Riis; Barry J. F. Biggs; Marty Flanagan (New Zealand Journal of Marine and Freshwater Research, 2003)
Seasonality in stream macrophyte biomass can have a profound effect on the flood risk in stream reaches as hydraulic resistance of macrophytes increases with increasing biomass. We studied the seasonality in total macrophyte biomass, and of eight common plant species, in eight streams over 1 year in the South Island, New Zealand. Biomass was generally highest in summer and lowest in winter, with biomass in winter being 40% less than the annual mean and 50% higher in summer. The season of maximum biomass varied among the eight species studied. Ranunculus trichophyllus and Veronica anagallis‐aquatica were most abundant only in summer; Elodea canadensis, Myriophyllum triphyllum, Rorippa nasturtium‐aquaticum, Potamogeton cheesemanii , and Potamogeton crispus were most abundant in summer or autumn, whereas Lagarosiphon major did not show any seasonal variations. These results can help predict the season of highest flood risk in South Island streams based on the predominant species in a stream reach, and thus when the most efficient time for weed cutting might be.

Larval development of the New Zealand geoduck Panopea zelandica (Bivalvia: Hiatellidae) - P. E. Gribben; B. E. Hay (New Zealand Journal of Marine and Freshwater Research, 2003)
The larval development of the New Zealand geoduck, Panopea zelandica , grown under culture conditions, was described through measurements of shell morphometry using video image analysis, photomicrographs, and scanning electron microscopy (SEM). Gametes were stripped from ripe broodstock and eggs fertilised with a dilute sperm solution. Developing larvae were maintained at 17 ± 1°C. Fertilised eggs developed into trochophores within 12 h and to D‐stage larvae (105.3 μm shell length) within 24 h. Larvae spontaneously settled after c. 16 days at c. 247 μm shell length. Measurements of shell morphology, including total length, total height, hinge length, length of anterior end, and umbo length and height were adequate descriptors of larval development. SEM indicated that the provinculum of D‐stage and developing veliger larvae lacked any teeth, although there was some development of a small lamelliform tooth on the hinge structure of newly settled post‐larvae. Prominent spines common on dissoconch shells of other hiatellid clams were absent in newly settled post‐larvae of P. zelandica . The data presented here are the first description of the larval development and larval biology of P . zelandica . The relative ease of spawning and rearing of P . zelandica suggests that the development of commercial hatchery technology for this species warrants further investigation.

Biological assessment of rivers in the Manawatu‐Wanganui region of New Zealand using a predictive macroinvertebrate model - Michael K. Joy; Russell G. Death (New Zealand Journal of Marine and Freshwater Research, 2003)
This study presents a river invertebrate and classification system (RIVPACS) type bioassessment methodology for the Manawatu‐Wanganui region of New Zealand. Aquatic macroinvertebrates and related physico‐chemical data were collected at 127 sites, with minimal human impacts (reference sites) in 2000. The reference sites were classified into five groups based on their macroinvertebrate data using TWINSPAN. These biotic groupings were then applied to their corresponding physico‐chemical data and discriminant functions were obtained to assign sites into the biotic groups using the physico‐chemical data. The discriminant functions correctly allocated 72% of the sites to the correct classification group using a jack‐knife validation. The probabilities from the discriminant functions were used to predict macroinvertebrate assemblages and these were compared with observed macroinvertebrate assemblages. The model was then used to assess the health of 29 test sites with known impacts. All test sites were assessed as impacted based on the 10th percentile of the reference data. To evaluate the temporal reliability of the model, data available for 11 sites sampled in 1997 and 2000 were run through the model. The results of this comparison showed little variation in O/E ratios over time and the two sites classed as impacted in 1997 were also classed as impacted in 2000.

The Great Barrier Reef. History, Science, Heritage. By JamesBowen and MargaritaBowen. Published in 2002 by Cambridge University Press (www.cambridge.edu.au). 454 p., hardback. ISBN: 0–521–82430–3. Price: AU$ 79.95 (info@cambridge.edu.au). - Nick Gust (New Zealand Journal of Marine and Freshwater Research, 2003)

Headwater stream response to grassland agricultural development in New Zealand - Ralph H. Riley; Colin R. Townsend; Dev K. Niyogi; Chris A. Arbuckle; Kathi A. Peacock (New Zealand Journal of Marine and Freshwater Research, 2003)
Agricultural development of native grasslands may change stream physico‐chemistry in ways that provide both subsidies and stresses to the system. The aims of this study were to determine: (1) which physico‐chemical parameters respond most strongly to agricultural development; (2) how biodiversity, community composition, and food‐web structure responded to these changes; and (3) to determine the balance between negative and positive impacts of these subsidies and stresses based on the analysis of 18 headwater streams. Developed pasture streams had increased nutrient loading, alterations to streamside vegetation, increased fine sediment composition, and lower moss coverage of stream‐beds than undeveloped or lightly grazed native grassland catchments (which could not be distinguished from one another). These differences were associated with higher numbers of macroinvertebrate taxa and higher numbers of macroinvertebrates indicating that the net effects of these subsidies and stresses associated with agricultural development were positive within these headwater stream reaches.

Preliminary assessment of crustacean distribution patterns in New Zealand groundwater aquifers - M. R. Scarsbrook; G. D. Fenwick (New Zealand Journal of Marine and Freshwater Research, 2003)
Crustaceans were sampled in 17 groundwater wells at five locations in North and South Islands of New Zealand. Three sampling locations were associated with unconfined aquifers adjacent to gravel‐bed rivers, whereas the other two locations were distant from rivers, but associated with land‐based sewage effluent disposal sites. Crustaceans and basic physico‐chemical parameters were sampled in summer and winter. Total abundance varied from 1 to 1064 individuals/250 litre sample. Copepods dominated the fauna at four of the five locations, and were most abundant immediately downstream of a sewage effluent disposal area. Paraleptamphopus spp. (Amphipoda) was found at all five locations, and abundance was also greatest downstream of sewage effluent disposal areas. Several crustacean taxa were rare or limited in distribution, including the gammarid Paracrangonyx sp. and the anthurid isopod Cruregens sp. Syncarids were widely distributed, but found in low numbers, and no specimens were found immediately below sewage effluent disposal areas. We suggest that groundwater ecology in New Zealand is restricted by lack of knowledge of taxonomy and ecology of key groups, particularly the Copepoda.

Importance of different size classes of phytoplankton in Beatrix Bay, Marlborough Sounds, New Zealand, and the potential implications for the aquaculture of the mussel, Perna canaliculus - Karl A. Safi; Max M. Gibbs (New Zealand Journal of Marine and Freshwater Research, 2003)
Phytoplankton are recognised as the primary source of food for cultured mussels. Small phytoplankton ( a concentration as an accurate measure of phytoplankton food supply for mussels.

Fish communities in New Zealand rivers and their relationship to environmental variables - Ian G. Jowett; Jody Richardson (New Zealand Journal of Marine and Freshwater Research, 2003)
Fish abundance data from selected electric‐fishing records in the New Zealand Freshwater Fish Database (NZFFD) were used to identify riverine fish communities and to examine their relationship to environmental variables included in the NZFFD. Only 21 fish species, 18 native species, and three introduced salmonids, were present at 1% or more of the sites. We defined 12 fish communities characterised by a dominant species: two salmonid communities, two non‐diadromous native communities, and eight communities characterised by diadromous native species. Altitude and distance inland were the two most significant variables, reflecting differences between communities dominated by diadromous and non‐diadromous species. The next most important variables were related to the geographic location of the site. Other environmental variables that were highly correlated with the fish community assignments were stream width and percentage of native forest or farming land use in the catchment upstream of the site. Of the local habitat variables, percentage of cascade habitat and percentage of sand substrate were the most important discriminators between communities. Despite having only a limited set of broad‐scale environmental variables, we achieved 47% success in the prediction of community membership using multiple discriminant analysis, with another 21% of sites being near misses. A greater knowledge of barriers to migration of diadromous species and fine‐scale variables describing in‐stream habitat would probably increase the predictive ability of the model, although collection of such data is time consuming and therefore impractical on a national scale.

Spatial organisation and behavioural interaction of giant kokopu (Galaxias argenteus) in two stream pools differing in fish density - Bruno. O. David; Rick. J. Stoffels (New Zealand Journal of Marine and Freshwater Research, 2003)
The spatial organisation and behavioural interactions between giant kokopu (Galaxias argenteus) of varying sizes were investigated in two stream pools which varied in fish density. The spatial distributions offish in Pool A were more exclusive, exhibited less overlap, and appeared to be more stable than those for fish in Pool B. The distinct difference observed between the two pools may have been influenced by fish density which was lower in Pool A (0.27 fish/m 2 ) than in Pool B (0.51 fish/m 2 ). A linear, size (weight) related dominance hierarchy appeared to exist within both pools whereby the heaviest individual was the most dominant. Though primarily nocturnal in habit, the social structure and behaviour of giant kokopu (when active during the day) was comparable to that exhibited by other drift‐feeding fish in the Northern Hemisphere.

Metazoan parasites of yellowtail kingfish, Seriola lalandi lalandi , in New Zealand: Prevalence, intensity, and site preference - N. J. Sharp; C. W. Poortenaar; B. K. Diggles; T. J. Willis (New Zealand Journal of Marine and Freshwater Research, 2003)
The prevalence and intensity of metazoan ectoparasites on the skin and gills of kingfish, Seriola lalandi lalandi (Carangidae), collected from White Island (n = 32), Ranfurly Banks (n = 7), and Three Kings Islands (n = 7), is reported. Kingfish were host to two monogenean and four copepod ectoparasite species, Benedenia seriolae, Zeuxapta seriolae, Caligus lalandei, Caligus aesopus, Neobrachiella spp., and Lernanthropus spp., respectively. B. seriolae and C. lalandei infect the skin, whereas the remaining parasites were located on the gills. All parasites exhibited considerable variability in the prevalence and intensity of infection. A few kingfish were completely devoid of C. aesopus, Neobrachiella spp., and/or Lernanthropus spp., whereas others were infected by moderate numbers of these species. However, all kingfish were infected by B. seriolae and Z. seriolae . Therefore, it appears that acclimation of wild kingfish from the east coast of New Zealand's North Island into captivity will lead to the transfer of both B. seriolae and Z. seriolae , and that effective quarantine measures will be required to avoid introducing these parasites into broodstock systems. The site preferences of B. seriolae, Z. seriolae , and C. aesopus were also investigated. B. seriolae exhibited a preference for attachment on the lateral surfaces of the skin behind the dorsal fin, but forward of the anal fin. Z. seriolae displayed a preference for attachment on gill arches 2 and 3, particularly in gill filaments located in the upper regions of the buccal cavity. C. aesopus most commonly occurred on the gill arch.

How well do New Zealand's stream‐monitoring indicators, the macroinvertebrate community index and its quantitative variant, correspond? - A. E. Wright‐Stow; M. J. Winterbourn (New Zealand Journal of Marine and Freshwater Research, 2003)
The Macroinvertebrate Community Index (MCI) and its quantitative version (QMCI) were developed to provide measures of organic pollution in streams on the Taranaki Ring Plain, New Zealand. Subsequently, they have been used widely to evaluate “river health” in many running water environments throughout New Zealand, although their suitability as general‐purpose monitoring tools needs evaluation. In the present study, the MCI and QMCI were calculated from fixed‐count macroinvertebrate data for 230 stream and river sites in Canterbury, New Zealand. Values ranged from 60 to 135 (MCI) and 2.0 to 8.8 (QMCI). The two indices ranked sites similarly (r s = 0.86), but the distribution of sites among published degradation bands (Stark 1998) differed. The MCI placed most sites in the “doubtful quality, or possible mild pollution” and “probable moderate pollution” categories, whereas the QMCI assigned most sites to the “clean water” and “probable severe pollution” groups. This implies either that category assessment was more conservative with MCI, or that the boundaries between groups are not equivalent. Since the two indices are alternative procedures with the same purpose, and results need to be transmitted to managers and others, descriptively, we consider this needs rectifying. Proposals for the modification of category boundaries are provided. Further, because the MCI and QMCI are influenced by factors other than water and habitat quality, and these are not well understood, index scores may provide an unrealistically precise measure of stream health in some circumstances. Low‐level identification (order, class, phylum) of fixed‐count data ranked sites in a similar way to conventional taxonomic resolution, but this relationship was stronger for QMCI (r s = 0.93) than for MCI (r s = 0.81).

Attraction of migratory inanga (Galaxias maculatus) and koaro (Galaxias brevipinnis) juveniles to adult galaxiid odours - Cindy F. Baker; Brendan J. Hicks (New Zealand Journal of Marine and Freshwater Research, 2003)
The response of migratory galaxiid juveniles, inanga (Galaxias maculatus) and koaro ( G . brevipinnis) , to the odours of adult galaxiids was tested in a two‐choice chamber apparatus. Both conspecific and heterospecific odours were tested. Inanga juveniles were attracted to adult inanga ( G. maculatus) , banded kokopu (G. fasciatus) , and koaro ( G . brevipinnis) odours. However, they were not attracted to odours from common bullies (Gobiomorphus cotidianus) . Koaro juveniles exhibited a species‐specific attraction to adult koaro odours only. These results demonstrate inanga juveniles can discriminate and are attracted to adult galaxiids during their migratory phase, whilst migratory koaro juveniles exhibit a species‐specific attraction to adult odours similar to the pheromonal attraction previously described for juvenile banded kokopu. This strengthens the hypothesis for the use of pheromonal cues in stream and habitat selection by amphid‐romous galaxiids.

Observations of sea‐level variability in Ross Sea, Antarctica - Derek G. Goring; Alex Pyne (New Zealand Journal of Marine and Freshwater Research, 2003)
Data from a new sea‐level recorder station at Scott Base on Ross Island and from a long‐established sea‐level recorder at Cape Roberts are analysed for tides and storm surge. Tides are primarily diurnal and their amplitude reduces to almost zero every 13.66 days, corresponding to the Moon's crossing of the equator. Global tide models are shown to give a poor fit with observations in Ross Sea, and although a local tide model gives a better fit for phase, the amplitudes are still not accurate. The only atmospheric tide that is significant is the semidiurnal solar tide whose amplitude is much larger than empirical models predict. Storm surge can be largely explained by changes in atmospheric pressure. Significant storm surge events are infrequent compared to locations at lower latitudes.

Genetic and morphological evidence for a single species of pink ling (Genypterus blacodes) in New Zealand waters - P. J. Smith; C. D. Paulin (New Zealand Journal of Marine and Freshwater Research, 2003)
Two species of ling, Genypterus blacodes (Forster in Bloch & Schneider, 1801) and G. microstomus (Regan, 1903) have been recorded from New Zealand and Australian waters; a third species, G. tigerinus (Klunzinger, 1872) has been recorded from Australia. Specimens of ling collected from northern, central, and southern localities in the New Zealand Exclusive Economic Zone (EEZ), and specimens of G. blacodes from Australia were shown to be similar with respect to partial sequences of mitochondrial (mt)DNA, and morphometric and meristic characters. DNA sequences of part of the cytochrome b and control region showed that G. blacodes from Tasmania and New Zealand differed by 1/291 and 4/284 nucleotides respectively, but there was much greater genetic differentiation between G. blacodes and G. tigerinus (14/291 and 14/284 nucleotides), and between G. blacodes and G. capensis (23/291 and 8/284 nucleotides). MtDNA haplotypes within New Zealand show that G. blacodes is subdivided into northern and southern stocks. It is concluded that ling in New Zealand represent a single species referable to G. blacodes , and that G. microstomus Regan is a junior synonym.

Age and growth of Cheilodactylus fuscus , a temperate rocky reef fish - Michael Lowry (New Zealand Journal of Marine and Freshwater Research, 2003)
To provide information on age and growth of red morwong (Cheilodactylus fuscus Castelnau), populations were sampled from eight locations over a 2.5‐year period with the majority of fish sampled from six sites within Sydney Harbour, New South Wales, Australia. Transverse thin sections of otoliths taken from a total of 347 fish were used to determine age. Age estimates were validated using oxytetracycline (OTC) marking and marginal increment techniques. Validated otoliths indicated that this species forms one annulus per year over an extended period from April to October. Age varied from “0” ( (t 0 = ‐1.8, k = 0.32, L = 37.64) indicated that growth is most rapid over the first 6 years, with fish being close to their asymptotic length by 7 years. There was no significant difference in length between sexes although females were significantly older than males. Comparisons of growth curves did not indicate any significant differences in the rate of growth between sexes.

Responses of crustacean zooplankton to seasonal and tidal salinity changes in the coastal Lake Waihola, New Zealand - Catherine J. Hall; Carolyn W. Burns (New Zealand Journal of Marine and Freshwater Research, 2003)
Lake Waihola is a shallow, tidal, coastal lake that receives brackish inflows resulting in salinities of up to 4.8‰. We determined the importance of salinity and tidal currents on crustacean zoo‐plankton abundance and distribution in this lake over 2 years. Tidal currents were traced using drogues, and zooplankton was sampled over tidal cycles. Tidal currents reached velocities of 35 cm s –1 closest to the tidal inlet channel. Salinity explained 26% of the variation in the abundance and species composition of the zooplankton assemblage, and accounted for >60% of the species‐environment correlation. Increases in salinity resulted in a change in crustacean dominance from the freshwater calanoid copepod, Boeckella hamata Brehm, and cladoceran, Daphnia carinata King, to the estuarine copepod, Gladioferens pectinatus Brady. The abundance of D. carinata was negatively correlated with chlorophyll a concentrations, although chlorophyll a was not correlated with salinity. Future increases in salinity and tidal currents may cause significant changes in the zooplankton community structure.

New Zealand fish: a complete guide. By ChrisPaulin, CliveRoberts, AndrewStewart, and PeterMcMillan. First published in 1989. Reprinted in 2002 by Te Papa Press, Museum of New Zealand Te Papa Tongarewa, Wellington, New Zealand. 279 p. ISBN: 0–909010–85–4. Price: NZ$39.95 (email: mcmedia@xtra.com.nz).Hook up on kingfish. By MarkKitteridge. Published in 2001 by Reed Publishing (NZ) Ltd, 39 Rawene Rd, Birkenhead, Auckland, New Zealand (www.reed.co.nz). 188 p., limpbound. ISBN 0–7900–0819‐X. Price: NZ$34.95 (email: kpower@reed.co.nz). - R. M. McDowall; Richard L. O'Driscoll (New Zealand Journal of Marine and Freshwater Research, 2003)

A new species of benthopelagic calanoid copepod of the genus Bradyidius Giesbrecht, 1897 (Calanoida: Aetideidae) from New Zealand - Janet M. Bradford‐Grieve (New Zealand Journal of Marine and Freshwater Research, 2003)
A new species of benthopelagic calanoid Copepoda is described from New Zealand. The species, Bradyidius capax n. sp. (Family: Aetideidae), is the second species of this genus to be recorded from New Zealand. B. capax females are close toB. armatus Giesbrecht, 1897 and B. rakuma (Zvereva, 1977). B. capax differs from these two species by a combination of its small size, hardly divergent rostral points, fusion line between pedigerous somites 4 and 5 not visible, posterior corners of pedigerous somite 5 directed straight posteriorly (not divergent in dorsal view), seminal receptacles occupy 57% of length of genital double somite measured ventrally, and antennal exopod segment 1 with small seta. The distribution of B. spinifer Bradford, 1969 is extended along the continental slope of north‐eastern New Zealand and some features previously undescribed, are illustrated.

Marine species of Ainudrilus and Heterodrilus (Oligochaeta: Tubificidae: Rhyacodrilinae) from Hainan Island in southern China - Hongzhu Wang; Christer Erséus (New Zealand Journal of Marine and Freshwater Research, 2003)
Six species of Rhyacodrilinae (Oligochaeta: Tubificidae) are reported from intertidal and shallow water subtidal habitats around Hainan Island in southern China. Four species are new to science: Ainudrilus pauciseta n. sp., Heterodrilus chenianus n. sp., Heterodrilus nudus n. sp., and Heterodrilus uniformis n. sp. Japanese material of Ainudrilus lutulentus (Erséus, 1984) is also briefly described. Hitherto, 27 species belonging to Tubificidae have been recorded from Hainan.

Comparison of coded abundance and fixed count rapid assessment techniques for biomonitoring in New Zealand streams - Ian C. Duggan; Mike R. Scarsbrook; John M. Quinn (New Zealand Journal of Marine and Freshwater Research, 2003)
We compared the performance of fixed count subsampling (100, 200, and 300 individuals) and coded abundance (rare, common, abundant, very abundant, very very abundant) with full count sampling for rapid assessment biomonitoring. Examining change in the Quantitative Macroin‐vertebrate Community Index (QMCI) and % Ephemeroptera, Plecoptera, and Trichoptera (EPT) values between sites upstream and downstream of pollution inputs, we found c. 1:1 relationships between assessments made using both rapid assessment methods and full counts. However, variability was greater using coded abundance, and to a degree that is likely to lead to incorrect assessments on occasion. The loss of information content in the data set, defined as Bray‐Curtis distances based on community composition between the two rapid assessment methods and those of full counts, was significantly greater using coded abundance than fixed counts. Assessment of stream invertebrate community composition using fixed counts, even as low as 100 animals, provided superior results to coded abundance in the two independent data sets tested.

Enhanced growth of longfin eels, Anguilla dieffenbachii , transplanted into Lake Hawea, a high country lake in South Island, New Zealand - Michael P. Beentjes; Donald J. Jellyman (New Zealand Journal of Marine and Freshwater Research, 2003)
Lake Hawea was stocked with c. 9500 juvenile longfinned eels (Anguilla dieffenbachii Gray) (mean weight 173 g) from the lower Clutha River of which a subsample of 2010 was tagged with coded wire tags. Three years later, the eel population in Lake Hawea was sampled resulting in 216 recaptures of transferred eels of which 42 were tagged. Eels had grown an average of 14 cm and 325 g (all recaptures). Growth rate of tag‐recaptures averaged 4.1 cm year –1 , was linear and faster than pre‐transfer when it was 2.4 cm year –1 (P 0.01). Eels transferred into Lake Hawea experienced accelerated growth and increased condition ascribed to low density (density dependent) and abundant food. Eels dispersed throughout the lake, but density was highest adjacent to “the Neck”, the point of release. Eels caught outside the Neck were larger and in better condition than those inside the Neck— further evidence of density‐dependent growth. Recaptured eels examined for sex were all females, indicating that either eels differentiated into females because density was low, or that males moved out of the lake to more preferred habitat downstream. Tag retention was high and tagging had no adverse effect on growth. Enhancement or stocking with longfins is viable for low density recruitment‐limited, high country lakes, but growth is likely to be density dependent.

Control of macrophytes by grass carp (Ctenopharyngodon idella) in a Waikato drain, New Zealand - R.D.S. Wells; H. J. Bannon; B. J. Hicks (New Zealand Journal of Marine and Freshwater Research, 2003)
Hornwort (Ceratophyllum demersum L.) and other aquatic macrophytes have historically been mechanically removed from the Rangiriri drain and Churchill East drain to maintain drain efficiency. As an alternative control method for the high plant biomass that accumulates at the end of summer, the effect of stocking diploid grass carp (Ctenopharyngodon idella L.) on the aquatic vegetation was evaluated in these Waikato drainage systems. At the start of the trial, both drains had a low diversity of aquatic macrophytes, and of the nine species (including the emergents), seven were exotic. Two months after grass carp were released to Churchill East drain (the treated drain) the four submerged and floating macrophyte species became scarce in the main drain. Over the same period, these species increased in biomass in Rangiriri drain (the untreated drain), where hornwort became dense and surface‐reaching and remained so for the duration of the trial. However, grass carp did not control submerged vegetation in smaller side drains or the shallow, upper parts of the main drain, or the marginal sprawling species and emergent species. The cost of leasing the grass carp was similar to the cost of clearing the drains mechanically, but grass carp provided continuous weed control. However, subsequent to this trial, 62 dead grass carp were found in Churchill East drain in February 2001, and weed cover subsequently increased. This illustrates that grass carp management in New Zealand agricultural drains can be problematic due to periodic fish kills.

Population genetic structure of the Canterbury mudfish (Neochanna burrowsius) : Biogeography and conservation implications - M. L. Davey; L. O'Brien; N. Ling; D. M. Gleeson (New Zealand Journal of Marine and Freshwater Research, 2003)
The population genetic structure of the Canterbury mudfish (Neochanna burrowsius) (Phillipps), a threatened endemic freshwater fish of New Zealand, was investigated using DNA sequence data derived from the mitochondrial D‐loop region. Samples were obtained from eight sites throughout the Canterbury region of New Zealand. Comparison of 845 bp from the tRNA‐pro end of the D‐loop from the 79 fish sequenced revealed low genetic diversity. Only 13 (1.5%) of the 845 bp analysed were found to be variable and only nine unique haplotypes were revealed. DNA distance estimates and phylogenetic reconstruction of these haplotypes demonstrated that there is little divergence between populations. Despite this, the population structure was significant, with just one haplotype (9) detected at more than one site in the wild. This genetic structuring is attributed to recent dispersal from a small historical population and periodic bottlenecks within individual populations. DNA divergence estimates show a significant subdivision between northern and southern populations, indicating a historical separation. It is recommended that future conservation management priorities take into account this genetic structuring in order to adequately conserve the limited genetic diversity within this species.

Benthic community dynamics during summer low‐flows in two rivers of contrasting enrichment 2. Invertebrates - Alastair M. Suren; Barry J. F. Biggs; Maurice J. Duncan; Liz Bergey; Paul Lambert (New Zealand Journal of Marine and Freshwater Research, 2003)
We examined the effects of summer low‐flow on invertebrate communities in two New Zealand rivers of contrasting enrichment and associated periphyton development. Quantitative benthic samples were collected and hydraulic measurements made from three runs in each river over a 6‐week period. Although hydraulic conditions and time since last flood disturbance were similar in both rivers, invertebrate communities were dissimilar. This dissimilarity reflected differences in periphyton communities within each river. The invertebrate community in the low enrichment river (Okuku River) was dominated by high numbers of “clean‐water” insect taxa, and this community changed little over time. Periphyton biomass was low here, and the community was composed of diatoms. Major changes occurred to the invertebrate community in the high enrichment river (Waipara River) over the summer, where the relative abundance of dominant invertebrate taxa changed from insects and snails to ostracods. Periphyton biomass was high in this river, which was originally dominated by diatoms and cyanobacteria but which became dominated by filamentous green algae. Changes to invertebrate communities were linked to this increase in filamentous green algae. Multiple regression analysis showed that changes to the invertebrate community in the enriched river were strongly correlated with the number of days at low flow, suggesting that successional processes occurred during the low‐flow period. Such changes may occur naturally during summer low‐flows in enriched rivers or could be exacerbated if velocities are reduced by abstraction. Our results suggest that a river's degree of enrichment should be considered when assessing minimum flows for consents or for the development of flow management guidelines.

Revision of the sponge genus Pleroma Sollas (Lithistida: Megamorina: Pleromidae) from New Zealand and New Caledonia, and description of a new species - Michelle Kelly (New Zealand Journal of Marine and Freshwater Research, 2003)
Diagnostic morphological characters for the sponge genus Pleroma , relicts from a diverse group of lithistid sponges (Suborder Megamorina: Family Pleromidae) that were once common in the north‐western European late Jurassic to the late Cretaceous (c. 140–65 Ma), are reviewed following examination of new collections of known species from northern New Zealand and the south New Caledonian slope. Before this work, only two living species of Pleroma were known, the genus holotype P. turbinatum Sollas from Fiji, and P. menoui Lévi & Lévi from south New Caledonian seamounts. A new species, P. aotea n. sp., is described from northern New Zealand waters, extending the suite of diagnostic characters to include nodulose megaclone desmas and amphiaster microscleres. Megaclone desmas, indistinguishable from those of P. menoui and P. aotea n. sp., are recorded from the Oamaru Diatomite in southern New Zealand (late Eocene), and the Tutuiri Greensand, Chatham Island (late Palaeocene), respectively. These published and new microfossil discoveries establish a disjunct geographic distribution for Pleroma in New Zealand.

Velocity measurements in the East Auckland Current north‐east of North Cape, New Zealand - Basil Stanton; Philip Sutton (New Zealand Journal of Marine and Freshwater Research, 2003)
Flow in the East Auckland Current (EAUC) system to the north‐east of North Cape, New Zealand is examined using data from two current meter mooring arrays, with supporting data from conductivity/temperature/depth (CTD) and satellite altimetry. Variable currents up to 45 cm s –1 were observed. The variability was partly attributable to changes in position and strength of the North Cape Eddy whose centre lies some 150 km offshore. The observed flows across the mooring line correlate well with those estimated from satellite altimetry. This gives confidence in the use of the satellite data to estimate the transport variability in the EAUC in the 1992–2001 period. No seasonal cycle was found in the volume transports but rather broadband variability at periods longer than 100 days.

A recent sponge, Pleroma aotea Kelly (“Order” Lithistida: Family Pleromidae), in the late Eocene Ototara Limestone of Otago, New Zealand - Michelle Kelly; Daphne Lee; Shane Kelly; John S. Buckeridge (New Zealand Journal of Marine and Freshwater Research, 2003)
Numerous remarkably well‐preserved lithistid sponges recovered from the late Eocene‐early Oligocene Ototara Limestone at Kakanui, North Otago, represent the first sponge body fossils to be described from the New Zealand Cainozoic. The sponges are scattered throughout a 1–3‐m‐thick volcaniclastic limestone horizon immediately overlying the Kakanui Mineral Breccia. The fossils are now solid calcite, the former siliceous skeleton having been replaced during diagenesis. The Kakanui sponges are the only known body fossils remaining from an extremely diverse sponge fauna which formed a major component of the benthos in the Kakanui‐Oamaru region in late Eocene‐early Oligocene times (c. 35–33 Ma). The sponge body fossils are described and compared with living sponges that have a similar flattened globose morphology. The fossils are morphologically indistinguishable from the living lithistid sponge Pleroma aotea Kelly (“Order” Lithistida: Family Pleromidae) from deep‐water seamounts and banks off north‐eastern New Zealand, and are significant in that they represent a stratigraphic range for the species of more than 35 million years. The present‐day distribution of P. aotea , limited to silica‐rich deeper waters, is in marked contrast to the relatively shallow warm water volcanic environments occupied during the Palaeogene. This restriction, and that of related lithistid sponges to silica‐rich deeper waters off northern New Zealand, is paralleled in other demosponges and several calcareous invertebrate groups such as barnacles, bryozoans, and crinoids.

Benthic community dynamics during summer low‐flows in two rivers of contrasting enrichment 1. Periphyton - Alastair M. Suren; Barry J. F. Biggs; Cathy Kilroy; Liz Bergey (New Zealand Journal of Marine and Freshwater Research, 2003)
Many foothill rivers in the eastern regions of New Zealand undergo severe reductions in flow during summer. These reductions are often exacerbated by abstractions for out‐of‐river uses. It has been observed that at such times some river ecosystems are more detrimentally affected by reduced flows than others. We hypothesised that the degree of degradation in river ecosystems during summer low‐flows is dependent on a river's enrichment status. We examined the effect of low flows on periphyton community dynamics in two Canterbury rivers of contrasting enrichment. Three runs in each river were sampled on four occasions over a summer low‐flow period, during which discharge was amongst the lowest on record for these rivers. Percentage cover of major periphyton groups on the riverbed was estimated across five transects in each run, and periphyton was scraped from five replicate rocks per run to quantify taxonomic richness, community composition, and chlorophyll a biomass. Periphyton communities in each river were quite different. Diatoms with a low biomass dominated the communities in the unenriched Okuku River. These communities did not change significantly in composition or biomass over the 6‐week study period. Conversely, in the enriched Waipara River, the communities had a high biomass and there was a succession in dominant taxa from diatoms and cyanobacteria to filamentous green algae over summer. This resulted in the Waipara River exceeding guidelines for the maintenance of in‐river recreational and fisheries values, whereas the Okuku River did not. Thus, degree of enrichment should be taken into account when assessing in‐river flow requirements. We suggest that enriched rivers will be more sensitive to flow abstraction (i.e., they will become more degraded), and so may require higher minimum flows to maintain river health, than unenriched rivers.

Movement patterns of mature spiny lobsters, Jasus edwardsii , from a marine reserve - S. Kelly; A. B. MacDiarmid (New Zealand Journal of Marine and Freshwater Research, 2003)
The maintenance of long‐term associations with particular reef sites is likely to have contributed to the rebuilding of the spiny lobster population (Jasus edwardsii (Hutton) (Decapoda: Palinuridae)) in the Leigh Marine Reserve, in northeast New Zealand. Between 1983 and 1985, 429 lobsters were tagged underwater with western rock lobster tags and antennae tags. Underwater tagging and commercial traps were used to tag a further 737 lobsters with T‐bar tags and antennae tags between 1994 and 1996. Twenty‐one percent of lobsters resighted (n = 323) between 1983 and 1985 maintained their association with a 15 ha reef inside the reserve for 1–8 years. Site association tended to increase with female size, whereas site association in males was relatively constant until 130 mm carapace length, and then markedly increased. Legal‐sized lobster abundance fluctuated seasonally, suggesting that a proportion of the population undertook larger‐scale movements beyond the reef. This was confirmed during a second tagging programme conducted between 1994 and 1996. About 30% of resighted lobsters (n = 212) moved 0.25–6 km from their tagging site and 20% crossed the boundary, either moving into or out of the reserve. These results indicate that although the Leigh Marine Reserve reduces spatial access to fishing grounds, a proportion of the lobster population moves out of the protected area and becomes susceptible to capture in the adjacent fishery.

Invasion of the Asian goby, Acentrogobius pflaumii , into New Zealand, with new locality records of the introduced bridled goby, Arenigobius bifrenatus - Malcolm P. Francis; Cameron Walsh; Mark A. Morrison; Crispin Middleton (New Zealand Journal of Marine and Freshwater Research, 2003)
The Asian goby, Acentrogobius pflaumii (Bleeker, 1853), is reported from New Zealand waters for the first time. It was collected by beach seine in 2001–02 from muddy substrata in the upper reaches of the Waitemata and Whangapoua Harbours. We suggest that A. pflaumii has been introduced to New Zealand, probably in ship ballast water. It may have arrived directly from its native range in the north‐west Pacific Ocean, or indirectly via Australia, which it invaded before 1996. The Australian bridled goby, Arenigobius bifrenatus (Kner, 1865), which is also thought to have invaded New Zealand via ballast water, is here recorded from three new locations, extending its known New Zealand range to five different harbours spanning c. 150 km of coastline. This species is more widespread than previously thought and appears well established. Both gobies have been found only on the east coast of the North Island.

Effects of turbidity on the ability of juvenile rainbow trout, Oncorhynchus mykiss , to feed on limnetic and benthic prey in laboratory tanks - David K. Rowe; Tracie L. Dean; Erica Williams; Joshua P. Smith (New Zealand Journal of Marine and Freshwater Research, 2003)
The feeding rate of juvenile rainbow trout, Oncorhynchus mykiss Richardson, 1836, on small (1–2 mm diam.) Daphnia spp. in laboratory tanks was not reduced by turbidity levels up to 160 Nephelometric Turbidity Units (NTU). Furthermore, the high feeding rates on larger, benthic prey (viz. Deleatidium spp. and chironomid larvae) in clear water (0 NTU) were maintained at turbidities up to 160 NTU. Therefore, any impairment of vision by increased turbidity did not affect the ability of trout to feed on these prey, and non‐visual senses may be used for the capture of such prey in turbid waters. Although trout were strongly size‐selective for both large chironomid and Deleatidium larvae in clear water, turbidities over 20 and 160 NTU, respectively, reduced size‐selection. Vision is therefore needed by trout to select larger prey. However, chironomid larvae were consumed by trout in the complete absence of light, so their ability to capture these prey in tanks was not dependent on visual cues. It is apparent that trout do use other senses such as the lateral line system to detect and capture such prey when turbidity levels are high and when light levels or water clarity are low. This ability is expected to offset any reduction in visual feeding caused by increased turbidity, and it helps explain the increased emphasis on epibenthic feeding by trout in turbid waters.

Seasonal variation in the reproductive activity and biochemical composition of the Pacific oyster (Crassostrea gigas) from the Marlborough Sounds, New Zealand - Jeffrey S. Ren; Islay D. Marsden; Alex H. Ross; David R. Schiel (New Zealand Journal of Marine and Freshwater Research, 2003)
Reproductive cycles of the Pacific oyster Crassostrea gigas (Thunberg) from the Marlborough Sounds, New Zealand, were followed between June 1998 and January 2000. Histological examination of the gonad confirms an annual cycle with a winter inactive period followed by rapid gonad development and a single short spawning period. The population gonad index correlated with seawater temperature and changes in tissue dry weight, condition index, and biochemical components. In winter, few individuals with early gametogenic stages were present and rapid development of primary oocytes (diam. 11 μm) occurred during spring (September‐November). The developmental rate and the diameter of mature oocytes (37 μm) was similar for the 1998 and 1999 seasons. For a standard 110‐mm‐length oyster, maximal tissue body weight and condition index were recorded in December. Rapid weight loss in January was length dependent and was attributed to spawning. Temperature was the environmental variable which best correlated with the timing of gametogenesis. Food availability (phytoplankton biomass) may have been responsible for inter‐annual variations. The biochemical composition (% glycogen, lipid, protein) of separated gonad and somatic tissues were variable seasonally and annually. Gametogenesis (oocyte diameter) was associated with increased gonad protein and glycogen and a decrease in lipid concentrations. These changes are similar to those in Pacific oyster populations from other parts of the world.

Distribution of fish in tributaries of the lower Taieri/Waipori rivers, South Island, New Zealand - Bruno O. David; Gerard P. Closs; Chris J. Arbuckle (New Zealand Journal of Marine and Freshwater Research, 2002)
The distribution of fish within eight small streams feeding into the lower Taieri and Waipori Rivers on the east coast of New Zealand's South Island was examined. A total of eight native and two introduced species were recorded. Eels ( Anguilla spp.) and giant kokopu ( Galaxias argenteus Gmelin) were the most widely distributed species being located in all streams surveyed. Common bullies ( Gobiomorphus cotidianus McDowall) and brown trout ( Salmo trutta Linnaeus) were also widely distributed being detected in seven and six of the streams respectively. Three streams of potential conservation significance were identified. These were Picnic Gully Creek which contained a significant population of banded kokopu ( Galaxias fasciatus Gray), a Category C threatened species, and Cullens and Alex Creeks which contained significant populations of giant kokopu, a Category B threatened species. The population of giant kokopu in Cullens and Alex Creeks currently represents the largest known population of this species on the east coast of New Zealand (excluding Southland). It has been suggested that brown trout may influence the distribution of native galaxiids. The longitudinal distribution of giant kokopu and brown trout in streams was examined at night using a continuous spotlight sampling approach. Distributions of these two species rarely overlapped at a local scale. Coarse habitat use data indicated that brown trout regularly occupied a variety of habitat types including modified agricultural channels. In contrast, giant kokopu rarely used agricultural channels being predominantly located in pool habitats.

Absolute geostrophic currents in the East Auckland Current region - P. J. H. Sutton; T. K. Chereskin (New Zealand Journal of Marine and Freshwater Research, 2002)
Absolute geostrophic currents are estimated for the full depth of the water column off the north‐east coast of New Zealand for February 1998. This is achieved by objectively‐mapping subsurface Acoustic Doppler Current Profiler (ADCP) data using horizontal length scales determined from repeat high‐resolution Expendable Bathythermograph (XBT) data and enforcing horizontal non‐divergence. The resulting 2‐dimensional map of velocity at a single depth is used as a level of known motion. Velocities at all other depths are calculated by combining this known motion with the geostrophic shear calculated from hydrographic measurements. The flow field exhibits the expected large‐scale features: the East Auckland Current (EAUC) and the North Cape Eddy. It also indicates that these flows were underestimated by the standard use of a 2000 m level of no motion, i.e., these features penetrate 2000 m. Flows at 2000 m are found to be as large as 30–40 cm/s with a mean of 17 cm/s. This is less than the maximum flows measured by deep current meters, but significantly higher than the mean. Comparisons of the ADCP‐referenced surface flow field with the surface flow field calculated by combining climatology and TOPEX/Poseidon sea‐surface height (SSH) show general qualitative agreement. The two independent flow estimates are similar in the core of the EAUC, with the differences being c. 10 cm/s, whereas the agreement further offshore is not as good.

Thermal marking of rainbow trout ( Oncorhynchus mykiss ) otoliths - Bryan Van Der Walt; Robert A. Faragher (New Zealand Journal of Marine and Freshwater Research, 2002)
A small‐scale experiment was done to test the feasibility of thermally marking hatchery‐reared rainbow trout ( Oncorhynchus mykiss Walbaum) fry that are released into rivers and impoundments in New South Wales (NSW), Australia. Fry of rainbow trout were exposed to two different 48‐h thermal cycles each of a cold and warm water period. One thermal regime consisted of a cold water period during which the temperature was reduced from 14 to 8°C for 18 h followed by a return to 14°C for 30 h. For the second thermal treatment, water temperature was reduced to 4°C for 10 h followed by a period of 38 h at 14°C. Thermal cycles were repeated 4 and 8 times for each thermal regime, respectively. Following a growth period after treatment, obvious marks were visible on all treated otoliths as distinct from control otoliths. The 10°C differential treatment created the most visible patterns and growth of these fish was not significantly different from control fish. This marking method could be applied to normal hatchery practices to evaluate the effectiveness of large‐scale rainbow trout stockings in NSW.

First encounter with a live male blanket octopus: The world's most sexually size‐dimorphic large animal - M. D. Norman; D. Paul; J. Finn; T. Tregenza (New Zealand Journal of Marine and Freshwater Research, 2002)
The first encounter with a live male blanket octopus, Tremoctopus violaceus Chiaie, 1830, illustrates the most extreme example of sexual size‐dimorphism in a non‐microscopic animal. Females attain sizes of up to 2 m long—almost 2 orders of magnitude larger than the 2.4‐cm‐long male. Weight ratios between the sexes are at least 10 000:1 and are likely to reach 40 000:1. Sexual selection and the unique defensive strategy of carrying cnidarian stinging tentacles may both have contributed to the evolution of this extreme size‐dimorphism. Such dimorphism is not seen in any other animal remotely as large.

Lipid content in rainbow trout ( Oncorhynchus mykiss ) fry and parr reared in spawning tributaries of Lake Taupo, New Zealand - Michel Dedual (New Zealand Journal of Marine and Freshwater Research, 2002)
The total lipid content of fry (25–30 mm) and parr (55–110 mm) of rainbow trout ( Oncorhynchus mykiss Richardson 1836) was measured in spring 1996 and 1997 and in autumn 1997 in six trout‐rearing tributaries of Lake Taupo, New Zealand. The fat content of fry was variable between streams and some streams had a higher inter‐annual variation than others. The fat content of parr was also variable among streams but no difference could be found between seasons. The streams that produced fry with high fat content did not always produce parr with high fat content.

Ecoregional differences in macrophyte and macroinvertebrate communities between Westland and Waikato: Are all New Zealand lowland streams the same? - I. C. Duggan; K. J. Collier; P. D. Champion; G. F. Croker; R. J. Davies‐Colley; P. W. Lambert; J. W. Nagels; R. J. Wilcock (New Zealand Journal of Marine and Freshwater Research, 2002)
We characterised water chemistry, aquatic habitat, macrophytes, and invertebrate assemblages in eight lowland streams—five in Westland, South Island, and three in the Waikato, North Island, New Zealand. Factors influencing invertebrate community structure over large (between ecoregions) and small (within an ecoregion) spatial scales were investigated. The Westland sites had generally lower nutrient concentrations, conductivity, and water clarity, and coarser substrates than the Waikato sites, reflecting differences in geological history, hydrology, and land‐use intensity. The macrophyte communities in each region were very different in species composition and structure, but seasonal abundance patterns in both regions were fairly typical of New Zealand streams in general. Alien obligate submerged macrophyte species were absent from the Westland lowland stream sites, and may partly reflect the isolated nature of this region where colonisation by asexual macrophytes would be difficult. Waikato stream invertebrate faunas were dominated by molluscs (mainly Potamopyrgus ) and crustaceans (mainly amphipods), whereas Epheme‐roptera, Trichoptera, and Coleoptera taxa dominated the Westland stream faunas. The overall structure of invertebrate assemblages appeared to be influenced by a combination of regional differences in substrate type, nutrient concentrations, water clarity, and macrophyte cover. Westland streams with more upstream pastoral development had higher proportions of molluscs than those with predominantly forested or scrub catchments. Our study suggests that large‐scale ecoregional differences may override smaller‐scale land‐use effects on lowland stream invertebrate communities, and that management strategies should be developed on an ecoregional basis for lowland stream ecosystems.

Fish effects on charophyte establishment in a shallow, eutrophic New Zealand lake - Mary D. De Winton; Aleki T. Taumoepeau; John S. Clayton (New Zealand Journal of Marine and Freshwater Research, 2002)
Fish exclosures were deployed within shallow, eutrophic Lake Rotoroa, Hamilton, New Zealand to assess the influence of an alien‐dominated fish population on establishment by charophytes. Replicated mesh exclosures were placed at sites differing in wave exposure and received transplanted charophyte oospores and plants, with identical material placed outside. Charophyte establishment from oospores and plant biomass were greater inside exclosures compared with outside. Wave exposure did not depress germling response and the effect of fish exclosures on charophyte establishment was least apparent at the most exposed site. Exclosures did not have a statistically significant influence on the light climate, and epiphytic algal development was similar or higher inside the exclosures. However, sediment mobilisation was lower inside the exclosures. Results suggest that fish were primarily responsible for the poor performance of unprotected charophytes in Lake Rotoroa, with fish effects on plants operating via direct disturbance or grazing.

Nutrient cycling and fluxes in Beatrix Bay, Pelorus Sound, New Zealand - M. Gibbs; A. Ross; M. Downes (New Zealand Journal of Marine and Freshwater Research, 2002)
Nitrogen (N) and light availability limit phytoplankton growth and hence regulate food supply for mussel farming in Pelorus Sound, New Zealand. In Beatrix Bay, a large 35‐m deep embayment off Pelorus Sound, the supply of N is heavily influenced by physical factors. Bottom intrusions of N‐rich or depleted oceanic water occur in the main channel of Pelorus Sound and N‐depleted, phytoplankton‐enriched Pelorus River water characterises the near‐surface low salinity field. Inside Beatrix Bay, nutrient cycling via phytoplankton uptake, sedimentation, and subsequent regeneration from the sediments by mineralisation, also has an important influence on the availability of N in the water column. However, almost continuous salinity or thermally induced density stratification, or both, within Beatrix Bay meant that the upper and lower water columns were often decoupled so that N regenerated from the sediments was not readily available in the upper water column, and phytoplankton settling from the upper water column may not reach the sediments directly below because of large horizontal transport. The N supply in the upper water column of Beatrix Bay, where the mussels are farmed, is most likely regulated by advection in and out of the bay from external sources. Conversely, the N concentrations below the pycnocline could be almost entirely supplied via mineralisation from the sediments. The rates of sediment N regeneration were seasonally dependent. During winter, when sedimentation exceeds mineralisation, N accumulates in the sediments at a rate of up to 10 mg m –2 day –1 , whereas in summer, when mineralisation exceeds sedimenation, N is lost from the sediments at rates of up to 9 mg m –2 day –1 .

Fish assemblages in the Hauraki Gulf, New Zealand - Terese H. Kendrick; Malcolm P. Francis (New Zealand Journal of Marine and Freshwater Research, 2002)
Species assemblages in the Hauraki Gulf, New Zealand, and the factors affecting them, were determined from abundance data collected from 1381 trawl tows by two research vessels during 1964–97. Correspondence Analysis and Ward's Cluster Analysis were used to identify assemblages, and Canonical Correspondence Analysis (CCA) to explore the relationships between the assemblages and depth, sediment type, latitude, longitude, and year. Twenty‐six species that occurred in more than 5% of the stations were assigned to four assemblages, and a further four species showed no affinities with other species. For four commercial species, there was no evidence of ontogenetic variation in assemblage membership. The CCA models explained only 11–12% of the variance in the data. Year was the most important explanatory variable, suggesting that between‐year variation in species abundance affected assemblage composition. Sediment type was also important for many species. Assemblage A species were most abundant at shallow ( 50 m) mud sites, and Assemblage D species at deep mud sites. Assemblage C species had varied habitat preferences. The commercially important Pagrus auratus and Nemadactylus macropterus preferred mud, and Chelidonichthys kumu preferred sand. Zeus faber was most abundant at muddy sites, but also occurred (sometimes abundantly) at sandy sites.

Identification of galaxiid nests, emigrating larvae and whitebait, using mitochondrial DNA control region sequences - Sjaan C. Charteris; Peter A. Ritchie (New Zealand Journal of Marine and Freshwater Research, 2002)
We used mitochondrial (mt) DNA sequences to identify nests, emigrating larvae, and whitebait of three species of diadromous galaxiids, collected from eight locations in Taranaki and Manawatu, New Zealand. DNA was extracted from whole larvae and fin clips, and a 416 base pair (bp) sequence of mtDNA control region was determined. Four Galaxias fasciatus Gray (banded kokopu) and 12 G. postvectis Clarke (shortjaw kokopu) nests were identified. Galaxias postvectis, G. fasciatus , and G. brevipinnis Günther (koaro) individuals were detected migrating downstream from drift samples collected between May and June 2001. Furthermore, we identified three species from samples of whitebait revealing three G. postvectis , six G. fasciatus , and three G. brevipinnis . Species of larval eggs, larvae, and whitebait can be accurately identified by molecular methods. These methods provide an opportunity to help in the understanding of nest habitat choice, hatching time, migration, and choice of rivers by whitebait species.

Cricotopus and Paratrichocladius ( Chironomidae : Insecta) in New Zealand, with description of C. hollyfordensis n. sp., and redescriptions of adult and immature stages of C. zealandicus and P. pluriserialis - I. K. G. Boothroyd (New Zealand Journal of Marine and Freshwater Research, 2002)
Cricotopus van der Wulp and Paratrichocladius Santos Abreu are among the most common genera of Chironomidae found in fresh waters throughout New Zealand. Imago, pupa, and fourth (final) instar larva of Cricotopus hollyfordensis n. sp. are described, and the male imagines, pupae, and larvae of Cricotopus zealandicus Hutton and Para‐trichocladius pluriserialis Freeman are redescribed from new material. C. hollyfordensis n. sp. can be distinguished from other Cricotopus species by antennal ratio and absence of tibial and abdominal markings in the male imago; shape and form of the thoracic horn, distinctive abdominal spinule patterns and lateral setae in the pupa; and mentum and mandible characteristics in the larvae. The combination of tibial and abdominal markings of the male imago; thoracic horn and abdominal spinule patterns of the pupa; and mentum and mandible characteristics of the larva distinguish C. zealandicus from P. pluriserialis and all other New Zealand Cricotopus species. P. pluriserialis is distinguished from Cricotopus species by the presence of normal and erect dorsocentral setae in the adult; smooth thoracic horn and distinctive abdominal spinule patterns of the pupa; mentum and mandible characteristics, supra‐anal setae longer than 2–3 abdominal segment lengths, and abdominal setae simple, never in tufts, in the larva. C. hollyfordensis n. sp. has been recorded from a fast flowing mountain

Influence of large woody debris on channel morphology in native forest and pine plantation streams in the Nelson region, New Zealand - Brenda R. Baillie; Tim R. Davies (New Zealand Journal of Marine and Freshwater Research, 2002)
The influence of large woody debris (LWD) on channel morphology was assessed in five pine plantation and five native forest streams in the Nelson region of New Zealand. LWD volumes averaged 127 m 3 ha –1 in pine plantation streams and 94 m 3 ha –1 in native forest streams. Most of the LWD in pine and native streams had no influence on channel morphology (78 and 54%, respectively). Those LWD pieces influencing channel morphology contributed mainly to sediment storage in both pine and native streams as well as flow deflection and debris collection in the native streams. Wood aligned either perpendicular or obliquely to stream flow and positioned on or partly buried in the stream bed had the greatest influence on channel morphology. There were twice as many pools in native streams as in pine streams, and scour processes formed the majority of pools. LWD influenced c. 50% of pool formation in both pine and native streams and increased pool variety. LWD volumes in these streams are low compared with Pacific north‐west streams of the United States, similar to streams in the subalpine forest of Colorado, and higher than volumes in the more modified streams of Europe. Similarities in pool forming processes, pool type, and spatial arrangement of wood influencing channel morphology are apparent between the streams in this study and streams of the Pacific north‐west and Colorado.

First record of a wild population of the tropical snail Melanoides tuberculata in New Zealand natural waters - I. C. Duggan (New Zealand Journal of Marine and Freshwater Research, 2002)
The thiarid snail Melanoides tuberculata (Müller, 1774), native to the Middle East and East Africa, is recorded from the wild in New Zealand for the first time from a geothermally influenced stream at Golden Springs, near Taupo. Introduction was most likely the result of one or more releases from tropical aquaria, although the timing of release is uncertain. Specimens were collected at temperatures of 29.0 and 30.4°C, and survival at these sites is likely dependent on the elevated stream temperatures. The possible spread of this species to other habitats, and potential effects on native thermal water communities, are discussed.

Genetic and meristic variation in black and smooth oreos in the New Zealand exclusive economic zone - P. J. Smith; P. J. McMillan; B. Bull; S. M. McVeagh; P. M. Gaffney; S. Chow (New Zealand Journal of Marine and Freshwater Research, 2002)
Meristic and genetic methods were used to determine the stock relationships of black Allocytus niger (James, Inada & Nakamura, 1988) and smooth oreo Pseudocyttus maculatus (Gilchrist, 1906) in the New Zealand Exclusive Economic Zone (EEZ). Samples were collected from four management areas—OEO 1 (south‐west), OEO 3A (Chatham Rise west), OEO 4 (Chatham Rise east), and OEO 6 (subantarctic) during the 1998 October‐December spawning period. Lateral line scale counts and pyloric caeca counts revealed differences between black oreo samples from OEO 6 and the other three OEO management areas. Lateral line scale counts in smooth oreo showed no significant differences between areas. Genetic analyses of four non‐coding regions of nuclear DNA and mitochondrial (mt) DNA haplotypes in black oreo showed no significant differentiation among the four management areas. Likewise for smooth oreo, genetic analyses of five non‐coding regions of nuclear DNA and mtDNA haplotypes showed no overall regional differentiation, although there was weak evidence at one locus for a difference between OEO 3A and OEO 6. The data do not reject the null hypothesis of a single genetic stock in New Zealand waters, and are typical of marine species with long pelagic juvenile stages.

Growth and population dynamics of crayfish Paranephrops planifrons in streams within native forest and pastoral land uses - Stephanie M. Parkyn; Kevin J. Collier; Brendan J. Hicks (New Zealand Journal of Marine and Freshwater Research, 2002)
Population dynamics of crayfish ( Paranephrops planifrons White) in streams draining native forest and pastoral catchments, Waikato, New Zealand, were investigated from September 1996 to July 1998. Crayfish densities were generally greater in native forest streams because of high recruitment over summer, but varied greatly between streams in both land uses. Peak densities in summer were 9 crayfish m ‐2 in native forest and 6 crayfish m ‐2 in pasture streams, but peak biomass in summer was much greater in pasture streams. Mark‐recapture data showed that crayfish, particularly juveniles, in pasture streams grew faster than in native forest streams, through both greater moult frequency and larger moult increments. Females reached reproductive size at c. 20 mm orbit‐carapace length (OCL) after their first year in pasture streams, but after 2 years in native forest streams. Annual degree days >10°C appeared to explain the differences in the timing of life cycles. Estimates of annual crayfish production (range = 0.8–3.4 g dry weight m ‐2 year –1 ) were similar in both land uses, and P/B ratios were between 0.95 and 1.2. Despite deforestation and conversion to pasture, crayfish in these Waikato hill‐country streams have maintained similar levels of annual production to those in native forest streams, although juvenile growth rates have increased and longevity has decreased.

Reproductive output of Crepidula fecunda females: Distribution of energy in the production of gametes and capsular walls - O. R. Chaparro; M. L. Flores (New Zealand Journal of Marine and Freshwater Research, 2002)
A study was undertaken on the distribution of energy in the reproductive output of Crepidula fecunda Gallardo 1979, a species which provides parental care of deposited eggs during their incubation period. A positive relationship was observed between the shell dimensions and dry tissue weight of the females which was not in turn related to the number of capsules incubated, nor with the size or dry weight of eggs deposited. Positive relationships were observed, however, between the female size and the capsular size and with the numbers of eggs per capsule and per spawning. No significant relationship was observed between the size of the females and the biochemical compositions of the individual eggs, but there was a positive relation between the sizes of the females and the total content of proteins, carbohydrates, and lipids deposited in each capsule wall and in all of the eggs of each spawning. The energetic cost per embryo varied from 0.045 to 0.049 J/embryo in females from 0.5 to 3.5 g tissue dry weight, respectively. Of the total energy invested per spawning, between 92 and 98% was in the eggs, and 2–8% in the capsular walls. Thus, parental care was relevant to the distribution of energy in the reproductive output, favouring production of gametes rather than of protective structures such as capsular walls.

Reproduction of the sea urchin Evechinus chloroticus (Echinodermata: Echinoidea) in a New Zealand fiord - Miles D. Lamare; Paul E. Brewin; Mike F. Barker; Stephen R. Wing (New Zealand Journal of Marine and Freshwater Research, 2002)
The reproductive cycle of Evechinus chloroticus (Val.) was examined at three (outer, mid, and inner) sites in Doubtful Sound, Fiordland over a 3‐year period. We found that sea urchins from all three populations had an annual gametogenic cycle, the timing of which was temporally and spatially consistent. Inter‐individual variation in the gametogenic cycle was noted within each population, however, initiation of gametogenesis was generally synchronous among males and females and among sites, occurring in May/June. Strong asynchrony in gamete maturation was observed in Deep Cove, occurring in males 4–5 months earlier than females. Spawning occurred in December at the inner and mid fiord sites, while occurring in January at the outer fiord site. Reproductive potential (maximum gonad index) and output (weight of gametes released/g of animal/year) varied spatially and temporally, where there was a consistent decreasing trend in reproductive potential and output with increasing distance away from the fiord entrance. Spatial variation in reproductive output may be associated, in part, with the strong ecological gradient found in Doubtful Sound, where there is a reported decrease in macrophyte biomass and cover towards the fiord headwaters. The implications of spatial differences in gonad production with respect to the population biology and fisheries management of E. chloroticus in the fiords are discussed.

Occurrence and use of Compsopogon coeruleus (Rhodophyta: Compsopogonaceae) in Fiji, South Pacific - G. Robin South; Posa A. Skelton (New Zealand Journal of Marine and Freshwater Research, 2002)
The rhodophyte Compsopogon coeruleus (Balbis ex C. Agardh) Montagne is newly recorded from Fiji, South Pacific. Plants occur in dense masses in the Wainivesi River in the province of Tailevu. Local villagers collect the plants and use them to cook a “pudding” with tinned fish, very similar to “puddings” prepared by coastal Fijians using marine species such as Gracilaria and Hypnea . This is the first documented account of the use of Compsopogon as a gelling agent in the preparation of human food.

Composition and flight periodicity of adult caddisflies in New Zealand hill‐country catchments of contrasting land use - Brian J. Smith; Kevin J. Collier; N. Jane Halliday (New Zealand Journal of Marine and Freshwater Research, 2002)
A total of 6085 adult Trichoptera (excluding Hydroptilidae) representing 12 families, 31 genera, and 56 species were collected by a combination of Malaise net and light trapping from July 1998 to July 1999 at three hill‐country sites of contrasting catchment land use (100% native forest, a pasture site with native forest headwaters, and 100% pasture) in the Waikato, northern New Zealand. Forty‐eight species of Trichoptera were collected from Malaise nets and 45 species from light traps. Eleven species of Trichoptera were only ever collected from the Malaise nets and seven species from only the light traps. At the native forest site, Malaise nets collected more species and taxa of conservation interest than did light traps, possibly reflecting diurnal activity or non‐attraction to light by some species. Several species of Trichoptera showed site specificity and most of these were found at the native forest site. Twenty‐eight species were active for at least 6 months of the year with at least four species active all year. A minimum overnight air temperature of at least 9°C was required to induce Trichoptera flight activity, but large‐scale flight activity may require temperatures greater than 14°C. Trichoptera with free‐living and net spinning larvae exhibited extended flight periods, and for three species examined there were bi‐modal activity peaks. Adult caddisflies with cased larvae which grazed on epilithic food resources generally had reduced flight periods and one species had a well‐defined, synchronous periodicity. These findings suggest flight periodicity may partly be a functional response to larval food availability.

Variability in spatial and temporal abundance of glass eels (Anguilla spp.) in New Zealand waterways - D. J. Jellyman; B. L. Chisnall; J. R. E. Sykes; M. L. Bonnett (New Zealand Journal of Marine and Freshwater Research, 2002)
The regional and annual variability in the abundance of newly arrived glass eels, Anguilla australis (Richardson) and Anguilla dieffenbachii (Gray), were examined using glass eel densities (n = 100 m –2 ) from electric‐fishing samples collected at 14‐day intervals over 5 years from 13 streams/ rivers throughout New Zealand. Although the density of shortfin eels exceeded that of longfin eels for any one year, the annual trends for both species were generally similar. Both species behaved independently, but significant factors affecting density were “year” and “region”, with the pronounced regional effect for longfin eels attributed to “coast” (east or west), but not “island” (north or south). There was no evidence of declining recruitment for longfin glass eels.

Distribution, seasonality, lengths, and feeding behaviour of whale sharks (Rhincodon typus) observed in New Zealand waters - C. A. J. Duffy (New Zealand Journal of Marine and Freshwater Research, 2002)
Data from 36 whale shark (Rhincodon typus Smith, 1828) sightings off north‐east North Island, New Zealand are summarised. Sightings were concentrated over the outer shelf and shelf break in areas influenced by the East Auckland Current at sea surface temperatures (SST) of 21–24°C. Sightings occurred from late spring to early autumn (November‐April) but were most frequent in midsummer (February) when upwelling along the north‐east shelf is weakest. The data indicate whale sharks occur off north‐east New Zealand most summers, including those when SST is colder than usual. A cluster of sightings and three observations of whale sharks feeding on schools of anchovy (Engraulis australis) near Whale Island, Bay of Plenty, suggest whale sharks may aggregate seasonally in this area. Estimated total lengths (TL) of 26 whale sharks ranged from 3.5 to 15 m, with 73% between 6 and 9 m TL.

Habitat use by juvenile lampreys (Geotria australis) in a large New Zealand river - D. J. Jellyman; G. J. Glova (New Zealand Journal of Marine and Freshwater Research, 2002)
Ammocoetes (larvae) of Geotria australis Gray, were sampled in a large South Island, New Zealand, river during summer to determine their distribution and habitat associations. Ammocoetes were widely distributed along the length of the river, being present at 66 of the 95 sites sampled. They ranged in density from 0 to 180 m –2 , and were associated with habitat type (mainly runs), overhead shade, and substrate features (depth or the proportion of fine sand). The amount of particulate organic matter was negatively correlated with ammocoete abundance.

Temporal and spatial quantification of aquatic invertebrate drift in the Maruia River, South Island, New Zealand - Karen A. Shearer; John W. Hayes; John D. Stark (New Zealand Journal of Marine and Freshwater Research, 2002)
We investigated temporal (day‐to‐day and season) and spatial (reach) variability of drift with the aim of guiding sampling protocol for quantifying drift at the whole river or reach scale. Overall, we found aquatic drift density and biomass varied considerably seasonally (CV = 72.9, 88.1) and to a lesser extent spatially (CV = 31.3, 30.7) and from day‐to‐day (CV = 45.2, 39.4). Although spatial and day‐to‐day variation in drift density and biomass were similar, sampling logistics suggest spatial sampling would be more cost‐effective and less time consuming. Drift density and biomass estimated from top samplers was often higher than estimates from samplers near the streambed or mid‐water column. A reliable estimate of mean densities and biomass at a site may require only two samplers— a top sampler and either a middle or bottom sampler. In our study, we calculated that sampling at four sites over 1 or 4 days at one site would be required to obtain a 95% CI within 50% of the mean drift density. Eight sites over 1 or 10 days at one site would be required to achieve a 95% CI within 25% of the mean drift density.

Photo‐identification of short‐beaked common dolphins (Delphinus delphis) in north‐east New Zealand: A photo‐catalogue of recognisable individuals - Dirk R. Neumann; Alexandra Leitenberger; Mark B. Orams (New Zealand Journal of Marine and Freshwater Research, 2002)
Photo‐identification has been established as a helpful tool in cetacean research. However, no study to date has attempted to apply this method to short‐beaked common dolphins (Delphinus delphis L.). We present here the results of two studies that were conducted concurrently in Mercury Bay and the Hauraki Gulf on the north‐east coast of New Zealand's North Island. Methods for distinguishing between individual dolphins are discussed. Sighting records of recognisable individuals indicate that some common dolphins move between Mercury Bay and the Hauraki Gulf (100 km distance), as well as between Mercury Bay and Whakatane (200 km distance). Common dolphin abundance and site fidelity appeared to be greater in the Hauraki Gulf than in Mercury Bay. A selection of photographs of distinct individuals is presented to allow future studies to compare their sighting records to ours, which may help establish the extent of home ranges, site fidelity, and possibly even longevity for common dolphins.

Abundance, distribution, and size structure of toheroa (Paphies ventricosa) at Ripiro Beach, Dargaville, Northland, New Zealand - Johyphen; Anne M. Akroyd; Kim A. R. Walshe; Russell B. Millar (New Zealand Journal of Marine and Freshwater Research, 2002)
The distribution of toheroa (Paphies ventricosa Gray) beds, and the abundance and size structure of toheroa at Ripiro Beach, Dargaville, New Zealand, were determined by a two‐phase stratified sample survey. The first phase was undertaken in February and March 1999 and the second phase in June 1999. The first phase located and sized 45 toheroa beds, and stratified the beds according to the observed density of siphon holes. A total of 53 transects were sampled. The transects were run perpendicular to the shoreline and positioned systematically within each stratum. Along each transect the sampling of beds was done at 5 m intervals using a 1 × 0.5 m quadrat. Outside of the beds, sampling was done at 10 m intervals. The total number of toheroa 75 mm (previous minimum legal size) was estimated to be 3.3 million with a standard error of 480 000. This abundance of legal‐sized toheroa is roughly comparable with numbers last seen at Ripiro Beach in the late 1960s. The total abundance of toheroa of all sizes was estimated to be 113.5 million with a standard error of 33 million. It appears that there has been good recruitment of + toheroa on Ripiro Beach and the abundance of toheroa of all size ranges has greatly increased since the previous survey in 1974.

Reproductive biology and population structure of the banded wrasse, Notolabrus fucicola (Labridae) around Kaikoura, New Zealand - Christopher M. Denny; David R. Schiel (New Zealand Journal of Marine and Freshwater Research, 2002)
Notolabrus fucicola Richardson, a large common labrid inhabiting rocky reefs around New Zealand and southern Australia, were collected monthly from December 1996 to February 1998 around Kaikoura, New Zealand. They were found to be asynchronous spawners and followed the typical labrid spring‐summer seasonal pattern of reproduction from July to December. Compared with other New Zealand labrids that are protogynous hermaphrodites, N. fucicola was found to be a secondary gonochorist, where individuals change sex before maturation. It is a dichromatic species but not sexually dimorphic. It is also monandric where only one morphological male type is present. Despite finding no transitional gonads, it is still possible that particular environmental or social conditions could induce sex change in at least a small proportion of fishes.

Density effects on juvenile shortfinned eel (Anguilla australis) cover preferences in replicate channels - G. J. Glova (New Zealand Journal of Marine and Freshwater Research, 2002)
The effects of density on day‐time cover preferences of juvenile (100–199 mm total length) shortfinned eels (Anguilla australis Richardson) were tested in replicate channels provided with natural (cobbles, macrophytes, woody debris) and artificial (shade, plastic pipes) cover during summer. The densities used were 10, 20, 30, 40, 50, 60, 80, 100, and 200 eels channel –1 (each channel = 2.4 m 2 ), with each density tested in triplicate, or better. Eels used cobbles and macrophytes almost exclusively, with cobbles being the most preferred and their use increased with increasing density; however, at 200 eels channel –1 , escape behaviour was evident during the night. In tests at 100 eels channel –1 , with only woody debris, plastic pipes, and shade sections available, the eels occupied woody debris, pipes, and shade in decreasing order. In further tests at 100 eels channel –1 , with cobbles, macrophytes and woody debris included, but with plastic pipes partially buried in the substrate and shade sections lowered to within 20 mm of the bottom, still only cobbles and macrophytes were used. Finally, in tests of 10, 50, and 100 eels channel –1 , with cover in each channel consisting of cobbles, macrophytes, woody debris, fallen sod (clumps of natural stream bank with riparian grasses), and modified shade (i.e., lowered to within 20 mm of the bottom with macrophyte rootlets attached to underside), eels preferred cobbles, shade, and fallen sod in decreasing order at all three densities. Overall, the findings of this study do not lend strong support to the hypothesis that juvenile eels use a greater variety of cover with increasing population density.

Effect of substrate stability and canopy cover on stream invertebrate communities - Erna M. Zimmermann; Russell G. Death (New Zealand Journal of Marine and Freshwater Research, 2002)
Disturbance can be an important determinant of stream benthic invertebrate community structure. Whether this is a result of the direct loss of invertebrates, an alteration to the food base of the community by the disturbance, or a combination of both, is never clear. We examined this question by conducting a disturbance experiment under artificial cover where low light limited periphyton growth and minimised the effect of disturbance on periphyton abundance. The experiment was conducted using baskets of natural substrate in a spring‐fed Taranaki Ring Plain stream, Taranaki, New Zealand during February and March 2000. Baskets were placed in the open or under cover and half were disturbed every week for 4 weeks. The artificial cover dramatically reduced periphyton biomass. Presence or absence of cover was the primary determinant of what invertebrate taxa dominated in the baskets, most likely as a result of differences in food resources. The filter feeding Coloburiscus humeralis dominated numerically in the covered baskets, whereas the generalist grazers Deleatidium spp., Beraeoptera roria , Orthocladiinae, and Diamesinae dominated numerically in the open baskets. However, cover had no effect on the overall abundance and species richness of the experimental baskets but disturbance reduced abundance and to a lesser extent species richness.

Influence of hydrologic exchange patterns on water chemistry and hyporheic invertebrate communities in three gravel‐bed rivers - Reece T. Fowler; Mike R. Scarsbrook (New Zealand Journal of Marine and Freshwater Research, 2002)
The influence of hydraulic exchange patterns on hyporheic water chemistry and invertebrate community composition was measured in three gravel‐bed rivers of southern Hawke's Bay, North Island, New Zealand. Based on patterns reported overseas we predict that down‐welling waters will be similar to surface waters in chemical characteristics and epigean animals will be more common in down‐welling waters than in up‐wellings, which would have a different chemical signature to the surface waters and a fauna dominated by hypogean invertebrates. Conductivity, pH, and temperature of hyporheic water were least like those of surface waters at up‐wellings in the groundwater‐fed Makaretu River. Only 6% of the invertebrate fauna of these up‐wellings comprised epigean animals. In contrast, in the groundwater‐recharging Tukituki and Waipawa Rivers, hyporheic water chemistry was similar to that of surface water in down‐wellings and 40% of the community comprised epigean animals by abundance. Significant increases (P 0.05) in species diversity and taxonomic richness was also identified in down‐welling zones compared with up‐wellings. Species diversity and taxonomic richness were lowest in up‐wellings in the Makaretu where hypogean animals dominated the hyporheic fauna. Species diversity and taxonomic richness were higher in down‐wellings than up‐wellings because more epigean taxa were present.

Population genetic structures of two New Zealand stream insects: Archichauliodes diversus (Megaloptera) and Coloburiscus humeralis (Ephemeroptera) - Ian D. Hogg; Pia Willmann‐Huerner; Mark I. Stevens (New Zealand Journal of Marine and Freshwater Research, 2002)
We examined the population genetic structure (allozyme variation) of two New Zealand aquatic insects: Archichauliodes diversus (Walker) (Megaloptera) and Coloburiscus humeralis (Walker) (Ephemeroptera); and tested the hypothesis that species with limited adult dispersal abilities would show high levels of genetic differentiation among hydrologically isolated habitats. Both species were characterised by low levels of within‐population genetic variability (e.g., H exp = 0.06 and 0.04 for A. diversus and C. humeralis , respectively). However, genetic differentiation among sites was considerably greater for A. diversus relative to C. humeralis (F ST = 0.57 and 0.03, respectively). A. diversus consisted of two genetically distinct groups in the North Island ( I = 0.96), and a third group from the South Island ( I = 0.67). By contrast, allelic differences among C . humeralis were minimal ( I > 0.99, in all cases), and appeared unrelated to geographic proximity or habitat type. We suggest that a combination of historic range changes and reproductive mechanisms, as well as contemporary dispersal capabilities, may be responsible for the observed population genetic structures of A . diversus and C. humeralis . Accordingly, generalisations based on present‐day dispersal abilities alone may be misleading particularly for island habitats such as New Zealand where gene pools may already be restricted.

Relative importance of surface and subsurface movement on benthic community recovery in the Makaretu River, North Island, New Zealand - Reece T. Fowler (New Zealand Journal of Marine and Freshwater Research, 2002)
Colonisation of macroinvertebrates following changes to the stream environment occurs rapidly through drift, oviposition, lateral movement, and vertical migration. To assess the influence of different sources of colonists on benthic macroinvertebrate community composition, a colonisation experiment using artificial substrate baskets was conducted in the braided Makaretu River in the southern Hawke's Bay (North Island, New Zealand). Both the numbers of taxa and individuals rapidly increased through time in baskets only allowing drifting and surface crawling invertebrates (surface), baskets only allowing invertebrates migrating from the hyporheic zone (hyporheic), and baskets that allowed both (controls). The numbers of taxa and density of individuals indicated that the artificial substrate baskets were similar to the benthos after 14 and 28 days, respectively. However, overall benthic community composition was not similar to the surrounding benthos until Day 42 in all three basket treatments. The colonisation rates identified from artificial baskets in the Makaretu River are consistent with other colonisation experiments undertaken in New Zealand and overseas. Elmidae (Coleoptera) was most abundant within surface treatments until Day 28 after which Deleatidium spp. (Ephemeroptera) became dominant. The abundance of Elmidae and Deleatidium in the control treatments was consistent with colonisation patterns in the surface baskets. Deleatidium dominated baskets allowing access from the hyporheic zone throughout the experiment. It appears that Elmidae colonise quickly in greater numbers by drifting and/or crawling and Deleatidium colonises more slowly from the hyporheic zone, eventually replacing Elmidae as the most common animal. This indicates that the hyporheic zone provides a source of invertebrate colonists later during community recovery, whereas drifting and/or crawling provides colonists early during recovery.

Two‐phase stratified random surveys on multiple populations at multiple locations - Bryan F. J. Manly; Jo‐Anne M. Akroyd; Kim A. R. Walshe (New Zealand Journal of Marine and Freshwater Research, 2002)
The two‐phase random stratified sampling design proposed by Francis (1984) was designed for situations where prior information is insufficient to ensure an efficient allocation of sampling effort to different strata. It involves taking a first‐phase sample, and then using the data from this to allocate a second‐phase sample which compensates for any shortcomings of the first‐phase sample. Here we generalise this method to situations where several species are sampled simultaneously, and at several locations. The method then uses the first‐phase sample results to decide how best to allocate a second‐phase sample to locations and strata. We provide the results of a simulation study based on model populations of shellfish which demonstrates the effectiveness of the method. We use a survey of cockles, pipis, and tuatuas on 11 Auckland Fisheries Management Area beaches as an example of its use.

Effect of three conditioning diets on the fatty acid composition of gonads and muscle of Argopecten purpuratus - Hernán Palma‐Fleming; Jorge M. Navarro; Eduardo Peña; Gloria Martínez (New Zealand Journal of Marine and Freshwater Research, 2002)
Mature specimens of Argopecten purpuratus (Lamarck, 1819), obtained from the Culture Center of Tongoy Bay, northern Chile were conditioned at 20°C and fed three different diets (mixture of pure microalgae, microalgae supplemented with a lipid emulsion, and microalgae supplemented with carbohydrates). Fatty acids were analysed at 0, 18, 38, 58, and 72 days of gonad conditioning. Both muscle and gonads showed a significant decrease in the relative distribution (weight % of total fatty acids) of saturated, monounsaturated, and n‐6 polyunsaturated fatty acids (mg/g dry weight). Generally, an increase of the n‐3 polyunsaturated group was observed for gonads until Day 58, thereafter a decrease was observed, probably as a result of environmental stress. A similar trend was observed for eicosapentaenoic and docosahexaenoic acids. n‐3 polyunsaturated fatty acids were the most preserved fatty acids, suggesting their importance as essential fatty acids for gonad maturation. The lipid‐supplemented diet afforded the best gonadal maturation and spawning occurred after 72 days.

Natural diet of the seahorse Hippocampus abdominalis - Chris M. C. Woods (New Zealand Journal of Marine and Freshwater Research, 2002)
This investigation examined the diet of adult wild seahorses, Hippocampus abdominalis Leeson 1827, from Wellington Harbour, New Zealand. Diet of seahorses (n = 59) collected from shallow subtidal macroalgal stands consisted largely of crustaceans, in particular amphipods (e.g., caprellid and ischyrocerid amphipods), caridean shrimp (i.e., Hippolyte bifidirostris) , and peracarids (i.e., the mysid Tenagomysis similis) . There were no differences in diet between male and female seahorses. Smaller seahorses consumed a greater amount of crustaceans than larger seahorses, as a result of the greater proportion of amphipods in their gut contents. There were some seasonal differences in diet, with amphipod consumption peaking in spring and summer, and decapod consumption lowest in autumn.

Uptake of palytoxin‐like compounds by shellfish fed Ostreopsis siamensis (Dinophyceae) - Lesley Rhodes; Neale Towers; Lyn Briggs; Rex Munday; Janet Adamson (New Zealand Journal of Marine and Freshwater Research, 2002)
Greenshell™ mussels (Perna canaliculus Gmelin), scallops (Pecten novaezealandiae Reeve), and Pacific oysters (Crassostrea gigas Thunberg) were fed with a New Zealand strain of mass cultured Ostreopsis siamensis Schmidt (for 27 and 84 h and with 1.5 × 10 6 or 8.6 × 10 6 cells, respectively) under laboratory conditions. The microalgal cells contained 0.3 pg palytoxin equivalents cell –1 (as determined by the haemolysis neutralisation assay (HNA) of Bignami (1993)) and extracts of these cells were toxic to mice after intraperitoneal injection. No palytoxin‐like material was detected either in the hepatopancreas or the muscle and roe of mussels fed O. siamensis . Oysters contained detectable amounts of toxin in hepatopancreas muscle, and roe while higher concentrations were present in the hepatopancreas of scallops. Extracts of control shellfish (tested biotoxin free and not fed O. siamensis) were toxic to mice, and there was no definitive evidence that feeding shellfish with O. siamensis at the levels employed in the present experiment increased the toxicity of shellfish tissue extracts to mice.

Genetic differentiation between the New Zealand and Falkland Islands populations of southern blue whiting Micromesistius australis - A. W. Ryan; P. J. Smith; J. Mork (New Zealand Journal of Marine and Freshwater Research, 2002)
The southern blue whiting Micromesistius australis (Norman, 1937) is found in two geographically distinct areas, the South Atlantic and south‐west Pacific Oceans. To date there has been no appraisal of the genetic relationships between the populations in these two areas. Here, we present analyses of New Zealand and Falkland southern blue whiting using mini‐ and microsatellite loci. Two out of six loci show highly significant allele frequency heterogeneities between the two areas, strongly suggesting genetically distinct populations.

Antarctic Intermediate Water variability in the northern New Zealand region - Basil R. Stanton (New Zealand Journal of Marine and Freshwater Research, 2002)
In the region between 30°S and northern New Zealand, vertical salinity profiles through the core of the Antarctic Intermediate Water (AAIW) show a high degree of spatial and temporal variability, and this variability is much larger than that found in nearby ocean areas. Characteristic features are interleaving of salinity layers and large changes in the salinity minimum between adjacent stations. Quantifying the changes through the calculation of an intrusion index highlights the degree of variability and the importance of boundary mixing along the New Zealand slope. However, the main cause of the variability is the meeting and mixing of higher salinity AAIW, arriving from the north‐west (having travelled around the subtropical gyre) with lower salinity AAIW arriving by more direct entry from the north‐east. These waters meet in the region through the action of the meso‐scale eddy field. Present data indicate that where strong salinity interleaving occurs, the length scales are of the order of 10 km and the time scales are of the order of a few days. Resolution of the processes at work will require studies on finer scales than presently available.

Use of the SHMAK clarity tube for measuring water clarity: Comparison with the black disk method - Cathy Kilroy; Barry J. F. Biggs (New Zealand Journal of Marine and Freshwater Research, 2002)
A metre‐long transparent tube for measuring visual water clarity was developed as part of the New Zealand Stream Health Monitoring and Assessment Kit (SHMAK) for use by non‐scientists. Water clarity measured using the tube (the horizontal sighting range of a black target) was compared with that measured using the standard “black disk” method (in which a black target is viewed horizontally underwater) to determine the feasibility of estimating black disk clarities from clarity tube readings. Readings using the two methods showed good agreement for waters with clarity c. 50 cm are lower than the black disk visibility and follow a logarithmic relationship with visibility, which enables useful readings to be made in clearer water. Independent testing of the relationship showed that black disk visibilities may be predicted with reasonable confidence in waters that contain very low concentrations of dissolved humic materials (yellow substance). In waters that are noticeably brown‐coloured, the relationship is less consistent especially at black disk visibilities of more than 1.5 m. Recommendations are given for the use of the clarity tube.

Two new species of Pseudostomella (Gastrotricha: Macrodasyida) with scaled triancres from the east coast of Australia - Rick Hochberg (New Zealand Journal of Marine and Freshwater Research, 2002)
Two new species of Pseudostomella from North Stradbroke Island, Australia, P. klauserae n. sp. and P. megapalpator n. sp., are characterised by scaled triancres, cuticular structures that until now were known only from one other member of the genus. The structure of the scaled triancres in both species is new: the triancre base is diamond‐ or triangular‐shaped with three shafts that arise to form feather‐like scales. P. klauserae n. sp. is characterised by scales arising from a diamond‐shaped triancre base, the distribution of cephalic papillae, and the abundance and distribution of anterior and lateral adhesive tubes. P. megapalpator n. sp. is distinguished by scales arising from a rounded‐triangular triancre base, large dorsal, digitiform papillae, and ventral adhesive tubes. The presence of two new species with scaled triancres allows for the formation of a novel species complex within the genus. An amended key to the species is included.

Pfiesteria shumwayae (Pfiesteriaceae) in New Zealand - Lesley L. Rhodes; Joann M. Burkholder; Howard B. Glasgow; Parke A. Rublee; Coy Allen; Janet E. Adamson (New Zealand Journal of Marine and Freshwater Research, 2002)
Pfiesteria shumwayae Steidinger et Burkholder is now known to be present in New Zealand and occurs in estuaries around the country. The presence of Pfiesteria was initially determined by a polymerase chain reaction (PCR)‐based detection assay, using oligonucleotide primers targeted at ribosomal DNA extracted from estuarine water and sediments. Presence was confirmed by isolation from fresh sediments in the presence offish (Oreochromis mossambicus) , followed by identification by scanning electron microscopy. The New Zealand isolates of P. shumwayae were ichthyotoxic in bioassays, but there is no historic evidence offish kills in New Zealand associated with the dinoflagellate.

Effects of sediment on fish communities in East Cape streams, North Island, New Zealand - J. Richardson; I. G. Jowett (New Zealand Journal of Marine and Freshwater Research, 2002)
We examined the effects of sediment on fish communities at 38 sites in the East Cape region of New Zealand. Many streams in this region are subject to high sediment loads, a natural situation that has been exacerbated by the conversion of native forest to pasture. The fish community consisted of diadromous native species common throughout New Zealand that require access to and from the sea. We found that site altitude and distance inland were important factors in determining the abundance and composition of the fish community. We used four measures as indices of sediment load: suspended sediment concentration, median substrate size, substrate stability, and the ratio of the wetted width to the width of the active (non‐vegetated) stream channel. Although all indices were correlated, the ratio of wetted width to width of active channel was most closely related to fish abundance and diversity. Fish abundance and diversity reduced as sediment load increased among streams, with up to nine fish species in streams with low sediment loads and only two species in streams with high sediment loads. In‐stream habitat also varied with sediment load; as load increased, depth and substrate size decreased and velocity increased. These results suggest that activities that increase sediment loads in rivers will have a negative impact on native fish communities in New Zealand.

Abundance of brown trout as related to littoral zone gradient in Lakes Te Anau and Manapouri, New Zealand - Rick J. Stoffels; Gerard P. Closs (New Zealand Journal of Marine and Freshwater Research, 2002)
Adult brown trout ( Salmo trutta L.) in lakes are primarily littoral/benthic foragers. We predicted that the distribution of adult brown trout in lakes would be shaped by foraging demands, and that they would be more abundant in gently sloping littoral areas, that is, littoral areas that have a greater space available to support benthic foraging habitats. To address this hypothesis, we measured abundance of brown trout among littoral areas with different gradients in Lakes Te Anau and Manapouri. There was a significant negative relationship between littoral zone gradient and relative abundance (CPUE) of adult brown trout. This result supports the hypothesis that brown trout aggregate in littoral areas with greater amounts of foraging habitat in Fiordland lakes.