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Introduced common carp (Cyprinus carpio) are a recognised threat to New Zealand’s freshwater ecosystems. In 2011, an invasive fish removal programme was undertaken in 16.8 ha Lake Ohinewai, a Waika...

New Zealand's Waikato River has had a short but intense history of development, primarily through land-use change and flow regulation in the upper river, and in the lower river through flood control works, non-native species invasion, and land-use intensification. The river undergoes sharp transitions across montane-flood plain-coastal environments over a short distance and under similar climate. Together with specialized life-history requirements of many native fish, these features provide valuable insights into large river ecology and management. Testing approaches to determine outcomes of water quality changes have highlighted the value of functional indicators over traditional biotic measures for monitoring anthropogenic impacts. Initiatives to enhance native fish populations in the lower river have included remediation of migration barriers to improve access to tributary habitat, enhancement of tidal spawning habitat, and traps and gates to limit movement of large pest fish into flood plain lakes for spawning. This example of a southern temperate large river system highlights the importance of recruitment habitat and connectivity for native fish communities dominated by migratory species. Their slender bodies provide opportunities to create semipermeable barriers that enable access to flood plain habitats while restricting larger invasive fish. Recent initiatives have increased momentum to restore the ecological health of this river, but the underpinning science to guide priority actions is often lacking, and there is limited monitoring over the scales and time frames required to evaluate effectiveness.

Responses of macroinvertebrate communities to human pressure are poorly known in large rivers compared with wadeable streams, in part because of variable substrate composition and the need to disentangle pressure responses from underlying natural environmental variation. To investigate the interaction between these factors, we sampled macroinvertebrates from the following: (i) submerged wood; (ii) littoral substrates 1.5 m) benthic habitats in eleven 6th- or 7th-order New Zealand rivers spanning a catchment vegetation land cover gradient. Cluster analysis identified primary site groupings reflecting regional environmental characteristics and secondary groupings for moderate gradient rivers reflecting the extent of catchment native vegetation cover. Low pressure sites with high levels of native vegetation had higher habitat quality and higher percentages of several Ephemeroptera and Trichoptera taxa than sites in developed catchments, whereas developed sites were more typically dominated by Diptera, Mollusca and other Trichoptera. Partial regression analysis indicated that the combination of underlying environment and human pressure accounted for 77–89% of the variation in Ephemeroptera, Trichoptera and Plecoptera taxa richness, %Diptera and %Mollusca, with human pressure explaining more variance than underlying environment for %Mollusca. Analysis of replicate deepwater and littoral samples from moderate gradient sites at the upper and lower ends of the pressure gradient indicated that total Trichoptera and Diptera richness and %Diptera responded to land use differences in these boatable river catchments. Responses to human pressure were substrate specific with the combination of littoral and deepwater substrates providing the most consistent response and yielding the highest number of taxa. These results indicate that multiple substrate sampling is required to document the biodiversity and condition of boatable river macroinvertebrate communities and that spatial variation in the underlying natural environment needs to be accounted for when interpreting pressure–response relationships. Copyright © 2012 John Wiley & Sons, Ltd.

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 T...

The New Zealand fish fauna contains species that are affected not only by river system connectivity, but also by catchment and local-scale changes in landcover, water quality and habitat quality. Consequently, native fish have potential as multi-scale bioindicators of human pressure on stream ecosystems, yet no standardised, repeatable and scientifically defensible methods currently exist for effectively quantifying their abundance or diversity in New Zealand stream reaches. Here we report on the testing of a back-pack electrofishing method, modified from that used by the United States Environmental Protection Agency, on a wide variety of wadeable stream reaches throughout New Zealand. Seventy-three first- to third-order stream reaches were fished with a single pass over 150–345 m length. Time taken to sample a reach using single-pass electrofishing ranged from 1–8 h. Species accumulation curves indicated that, irrespective of location, continuous sampling of 150 stream metres is required to accu...

The use of mussel spat ropes to enable the passage of banded kokopu (Galaxias fasciatus) past perched culverts was tested under laboratory conditions. A 0.5 m high simulated perched culvert was fitted with one of two UV stabilised polypropylene rope types: “Russet Loop” and “Super Xmas Tree”. Four randomised replicate trials using each rope type were conducted to test their respective abilities to provide passage for “fresh‐run” banded kokopu whitebait (migrating post‐larval juveniles). There was no statistical difference in performance between the two rope types, with both performing equally well over each 3 h trial. A high proportion of fish used the ropes to successfully negotiate the structure (mean >85% individuals per trial irrespective of rope type). The high rate of successful passage over a short time period suggests that these ropes may be an effective, affordable and potentially easy retrofit to perched culverts, particularly for native species with similar climbing capabilities to ban...

The small, transparent gobioid Gobiopterus semivestitus is recorded for the first time from New Zealand, from a tributary of Ngunguru River, near Whangarei, Northland. Distinctive features of its sexual dimorphism are reported, in particular enlarged fins and greatly enlarged jaw dentition in the male. The origins of this species in New Zealand waters are uncertain: it could have been here for some time, unobserved; it could have dispersed recently to New Zealand across the Tasman Sea from Australia; or it could have arrived in ships’ ballast water.

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/m2) than in Pool B (0.51 fish/m2). 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.

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 spec...