Distribution of fish in tributaries of the lower Taieri/Waipori rivers,South Island,New Zealand

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.     

Reproduction in Galaxias fasciatus Gray (Salmoniformes : Galaxiidae)

A study of the reproductive cycle was made on Galaxias fasciatus Gray from streams on Banks Peninsula, South Island, New Zealand. There was no spawning migration; adults remained in the usual adult habitat to breed. The course of gonad maturation showed that spawning occurred in the autumn, from the end of April to mid‐June. Most males matured at 2 years of age and most females at 4 years old. Egg numbers in the females varied from 3800 to 23 600. Males were predominant in age groups 1–4, females in the older age groups. Amongst fish of potential breeding age there was an excess of males. Circumstantial evidence suggested that eggs were laid among piles of water‐logged debris lodged in pools and backwaters. The larvae, which are briefly described, probably hatch during floods to be swept quickly downstream to the sea.     

Effects of turbidity on the migration of juvenile banded kokopu (Galaxias fasciatus) in a natural stream

Laboratory experiments have shown that the juvenile migratory stage of banded kokopu (Galaxias fasciatus (Gray 1842)) is more sensitive to turbidity than other native fish species and avoids turbidity levels of >25 nephelometric turbidity units (NTU). Field trials using juvenile fish collected from the Tarawera River and Hays Stream, New Zealand, were used to test the results from these laboratory experiments by measuring the effects of turbidity on the migration direction and rate for banded kokopu in a natural stream setting. In the stream setting, neither the migration rate nor the migration direction were affected at turbidity <25 NTU. At higher turbidity levels, significantly fewer fish migrated up stream within a given time period. Because there was rarely any downstream movement, this suggests the fish either halted or slowed their upstream movement. A slower rate of migration could result in fewer juveniles reaching adult habitat, and would account for the reduced abundance of adult banded kokopu in rivers that are turbid during the migration season. Achieving turbidity levels of <25 NTU in rivers and streams during the migration season would therefore help maintain upstream migrations and populations of banded kokopu, and hence other native fish species.     

Effects of riparian manipulation on stream communities in small streams: Two case studies

The effects of riparian manipulation in New Zealand are described for two case studies, one a short‐term study of the effects of the removal of riparian vegetation on fish, and the second, a long‐term study of the effect of re‐establishment of riparian vegetation on fish and benthic macro invertebrates. The first case study was an experiment carried out between November 2001 and May 2002. Overhanging bank vegetation and in‐stream wood were removed from short reaches of a small pastoral stream that had intact riparian margins, resulting in a change in stream structure with the formation of shallow uniform runs rather than pool and riffle structures as in unmodified reaches. The removal of bank cover and consequential instream habitat changes reduced inanga (Galaxias maculatus) densities by a factor of four within months of vegetation removal, showing the importance of instream cover and habitat to inanga. Adult longfin eel (Anguilla dieffenbachii) also became less abundant in the cleared reaches, but elvers (Anguilla spp.) became more abundant. In the second case study, pastoral sections in two small streams draining from native forest catchments were restored in 1995/96 by planting riparian vegetation and preventing stock access. After 10 years, the restoration efforts had more than doubled the numbers of giant kokopu (G. argenteus) and redfin bullies (Gobiomorphus huttoni), slightly increased numbers of banded kokopu (G. fasciatus), and decreased shortfin eel (A. australis) numbers by about 40%. The macroinvertebrate communities changed so that they became more similar to those at upstream native forest reference sites. These two case studies show that riparian margins can influence the composition of the fish and macroinvertebrate communities in small streams through the effects on cover, instream habitat and probably water temperature. Riparian restoration was most effective for the fish species that use cover and pool habitat.     

Reduced abundance of banded kokopu (Galaxias fasciatus) and other native fish in turbid rivers of the North Island of New Zealand

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

Timing and habitat of koaro (Galaxias brevipinnis) spawning in streams draining MtTaranaki,New Zealand

A spawning site of Galaxias brevipinnis Giinther was located in a New Zealand stream for the first time. It was at the edge of a riffle and only partially submerged. The habitat used for spawning matched that described for G. brevipinnis in Australia. Spawning was estimated to have occurred between late April and early May and the eggs hatched in late May. The species of fish spawning was identified by rearing the eggs through to identifiable juveniles and by DNA sequencing of one individual.     

Conservation status of New Zealand freshwater fish, 2009

The threat status of 74 freshwater and estuarine fish present in New Zealand was determined. Fifty-one native taxa were ranked of which 67% were considered Threatened or At Risk. A single species was classified as Extinct, the New Zealand grayling, which has not been observed since the 1920s. Four taxa were classified in the highest threat category, Nationally Critical, and a further 10 taxa as Threatened (Nationally Endangered or Nationally Vulnerable). Twenty taxa were ranked in the At Risk group with the majority ranked as Declining. Endemic galaxiids (Galaxiidae) dominated the Threatened and At Risk taxa. The majority (68%) belonged to the Galaxias genus, comprising 81% of recognised taxa in this genus and all five species in the genus Neochanna were also ranked as Threatened or At Risk. In addition to 51 native taxa, a further three fish species were considered colonists and 20 introduced species were classified as naturalised, although two of these are considered rare. The majority of the Threatened species occur in the Canterbury and Otago regions where a suite of rare non-migratory galaxiids exist. Threat mechanisms that were identified as causal in the decline of freshwater fish species were the impact of introduced fish species, declining water quality, effects of water abstraction, loss of habitat via land-use change and land-use activities, and river modifications.     

Spawning site selection,egg development,and larval drift of Galaxias postvectis and G. fasciatus in a New Zealand stream

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.     

The influence of habitat availability on juvenile fish abundance in a northeastern New Zealand estuary

Management of fish populations is often focused on the exploitation of adult fish. Maintaining the habitat requirements of all life stages may also be an important consideration. We investigated the value of structured habitat to juvenile fishes within a northeastern New Zealand harbour using artificial seagrass units (ASUs). Specifically, we deployed ASUs across treatments with high vs. low habitat manipulations. We hypothesised that if the abundance of recruiting juvenile fishes was greater on the high habitat availability treatments this would suggest that the availability of habitat was limiting juvenile fish abundance. Our analyses were focused on the four most abundant fishes that settled on our ASUs: snapper (Pagrus auratus); spotty (Notolabrus celidotus); trevally (Pseudocaranx dentex); and an assemblage of pipefish species. For snapper, spotty and pipefish, abundance was greater on the high habitat availability treatments. This result would be unlikely to occur if the availability of juvenile fishes was limiting, suggesting that juvenile fish abundance is more likely to be limited by habitat. In terms of spatial gradients, spotty abundance and size increased with distance into the harbour. The spatial gradient present for spotty indicates the importance of placing the habitat dependency of juvenile fish into a landscape context. Overall, these results demonstrate that maintaining structured habitats may be an important consideration for some valuable inshore fish populations in northeastern New Zealand.     

Diets of alpine galaxias (Galaxias paucispondylus Stokell) and longjawed galaxias (G. prognathus Stokell) in a South Island,New Zealand,high‐country stream

Thedietsofthealpinegalaxias(Galaxias paucispondylus Stokell, 1938) and the longjawed galaxias (G. prognathus Stokell, 1940) were studied in Deep Creek, a high‐country stream in the central South Island of New Zealand. Both species are small, slender fish with entirely freshwater life cycles. Their diets were very similar and consisted of aquatic invertebrates, dominated by the larvae of Deleatidium spp. (Ephemeroptera), Hydrobiosis spp. (Trichoptera), and Chironomidae (Diptera). Although diets partly reflected what was available in the stream, both fish selected soft‐bodied prey in preference to cased or harder shelled prey. Both species are probably nocturnal feeders.     

Growth characteristics,pigmentation, and the identificaton of whitebait (galaxias spp., Salmonoidea)

Definitions are given for stages in the development of five species of Galaxias, family Galaxiidae, which have marine larvae.

Larvae of Galaxias maculates attenuates and G. brevipinnis are large, and those of G. fasciatus relatively small as they enter fresh water from the sea. Development as whitebait involves shrinkage by about 25% in total length; the head length, considered separately, shrinks by about 15%. The ratio of standard length to head length alters from the larval to the adult value before positive growth recommences. These features are probably similar for G. postvectis and G. argenteus

Minimum observed pigmentation is described for the late larvae of G m. attenuates, G. brevipinnis, and G. fasciatus and for early whitebait of these and of G. postvectis and G. argenteus Subsequent development of melanophores and of colour pattern is described and figured. Large melano‐phores along the lateral line distinguish early whitebait of G. m. attenuates, but no distinguishing feature of pigmentation has been found in other species until the juvenile pattern is apparent. This pattern is characteristic for each species, and it persists in adult G. m. attenuates. G. argenteus has distinct juvenile and adult patterns, the latter being developed in a second, superficial, layer of pigment cells. Adult G. postvectis develop a distinctive fin colour pattern unlike other New ‐Zealand Galaxias; the superficial pigment layer is without definite pattern. In adult G. brevipinnis this layer resembles the persistent juvenile pattern and the two layers combined give a reticulate appearance. In G. fasciatus the juvenile pattern persists and develops as the fish grow; the superficial pigment layer is present in adults but is not usually apparent.

Until now positive identification of whitebait has depended on colour pattern. Recently recorded identifications of unpigmented whitebait are shown to be misleading. A key is given for the identification of early and late whitebait using absolute measurements as an important character.     

Emigrating larvae of koaro,Galaxias brevipinnis Günther (Teleostei: Galaxiidae), from the Otira River,New Zealand

Fish larvae were collected in stream benthic invertebrate drift nets from the Otira River, near Arthur's Pass, New Zealand during a study of benthic drift. They are identified as probably those of koaro (Galaxias brevipinnis Gunther) on the basis of estimates of myomere counts (indicating Galaxiidae or Retropinnidae); by a process of elimination of likely species on the basis of distance up stream, elevation, and habitat characteristics; and by determining fish species in the Otira River tributaries upstream of the sampling location. This comprises the first likely record of emigrating larvae of koaro, a species known to be diadromous by the return migrations from the sea of whitebait juveniles during spring. A newly hatched larva of koaro is described and figured.     

Laboratory culture of Galaxias maculatus and potential applications

Galaxias maculatus has considerable potential as a laboratory animal. Laboratory techniques used to maintain, artificially spawn, hatch, and rear this New Zealand native freshwater fish are described. Potential research applications for the fish, the eggs, and the larvae are outlined. The development of the larvae is described.     

The Canterbury mudfish,Galaxias burrowsius Phillipps,a vanishing species

Examination of available samples and of ecological knowledge of Galaxias burrowsius Phillipps (Galaxiidae) suggests that this species is confined to the Canterbury Plains and is now nearly extinct.

Possible reasons for its decline are analysed and it is suggested that this decline may have started nearly 1,000 years ago with the changes in the climate‐vegetation pattern. It has been hastened by the recent drastic transformation of the environment by European settlers. Distribution and habitats of two other New Zealand mudfishes, Neochanna apoda and N. diversus (Galaxiidae) are related to those of G. burrowsius     

Spatial and temporal distribution of landlocked Galaxias maculatus and Galaxias platei (Pisces: Galaxiidae) in a lake in the South American Andes

Galaxiids are present in many of the Andean lakes in southern South America. We studied landlocked Galaxias maculatus (Jenyns) and Galaxias platei Steindachner populations in a deep oligotrophic lake (Lake Gutiérrez, Patagonia, Argentina). Their temporal and spatial distribution, intralacustrine movements (horizontal and vertical), and spawning periods were analysed using several sampling techniques (ichthyoplankton net, seine net, gill net, and baited benthic taps). We identified the early life stages of both species based on their morphology and otolith shape. The free embryos of both species migrate to the limnetic zone, where they coexist as larvae, facing the same food availability and probably the same predation risk. Each species then moves on to its own juvenile and adult habitat: the littoral and benthic zone for G. maculatus and only the deeper benthic zone for G. platei. Their adult habitats and part of their spawning periods partly overlap.     

Description of the larval development of Galaxies maculatus in landlocked lentic and lotic systems in Western Australia

The larvae and larval development of Galaxias maculatus are described from a freshwater lake and a saline river in southwestern Western Australia. The size at hatching (7.0 mm total length) was similar to that recorded elsewhere for G. maculatus and the sequence of fin development (i.e., caudal, dorsal, anal, pectoral, and pelvic fins) was identical to that recorded for galaxiids generally. There were relative increases in the proportions of head length and body depth with larval growth and a decrease in proportion of pre‐anal length. Larvae from river habitats were smaller throughout larval stages of development than those from the lake. Fins of riverine fish began and completed development at a smaller size of fish than the lacustrine population, presumably as a response to the need for great motility at a smaller fish size in lotic environments.     

Effects of sediment on fish communities in East Cape streams,North Island,New Zealand

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.     

Demersal fish and habitat associations from visual surveys on the central California shelf

In 2004, we surveyed demersal fishes and habitats on the continental shelf off central California (65–110 m depth) using the occupied submersible Delta. Our objectives were to estimate the relative abundance of habitats and to examine demersal fish species composition, diversity, density, and sizes relative to these habitats. A total of 112 transects were completed covering 32 km of seafloor. A higher density of fishes was estimated in boulder and cobble habitats than in mud and brachiopod beds. More than 80% of the fishes were small, measuring 20 cm or less in total length. Species with small maximum size (primarily pygmy rockfish, Sebastes wilsoni, and blackeye gobies, Rhinogobiops nicholsii) accounted for nearly half (49%) of the total number of 12,441 fishes. Most fishes were immature, with only 4 of 20 harvested species having more than 50% of the individuals larger than the size at first maturity. Our study area on the continental shelf may be an ontogenetic transition zone for immature fishes before they move to their adult habitat on the slope. Alternatively, historical fishing pressure may have contributed to the lack of large, mature fishes in the survey area. Understanding the importance of these habitats to fishes at various life stages will improve our ability to assess these deepwater fish stocks and effectively manage these living resources on an ecosystem basis.     

Census survey approach to quantifying īnanga spawning habitat for conservation and management

Here, we describe a methodology for quantifying the spawning habitat of īnanga (Galaxias maculatus), a protected native fish species. Our approach is demonstrated with a survey of the Heathcote/ōpāwaho following the Canterbury earthquakes that produced unexpected findings. Spawning habitat was detected over a 2.5?km reach and the area occupied by spawning sites (75m²) was much larger than in previous records (ca.?21m²). Sites dominated by the invasive Phalaris arundinaceae were found to support high egg numbers. Spawning has not previously been recorded on this species and it is identified in the literature as a threat to spawning habitat. Considerable spatio-temporal variation was also detected in the location of spawning sites and pattern of egg production. Together, these aspects illustrate the need for a comprehensive survey methodology to reliably quantify spawning habitat. The Heathcote/ōpāwaho example shows the utility of our census approach for achieving this, and supporting habitat conservation objectives.     

Do predatory fish of benthic crustaceans vary between kelp and barren reef habitats in northeastern New Zealand?

Fish assemblages that included known predators of benthic crustaceans were compared between kelp and barren habitats in northeastern New Zealand using baited underwater video census methods. The benthic-feeding fish were observed in winter, spring/summer and autumn, as well as during night-time in spring/summer. Overall, the fish assemblages varied between barren and kelp habitat, being most marked in winter. Individual benthic-feeding species, such as grey mao mao (Scorpis lineolatus) and leatherjacket (Meuschenia scaber) were associated with barren habitat, while the spotted wrasse (Notolabrus celidotus) was more strongly associated with kelp habitat. The results suggest that changes in habitats on coastal reefs affect populations of species that are benthic predators, which may in turn influence the distribution and abundance of their prey species, such as juvenile spiny lobsters.