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This study used an experimental approach to compare the passage success of native and exotic fish species from the temperate Southern Hemisphere over an artificial baffled fish ramp designed for overcoming low-head (≤1.0 m) fish migration barriers. Passage efficiency was, on average, lower for the exotic species [koi carp (Cyprinus carpio), rudd (Scardinius erythrophthalmus) and rainbow trout (Oncorhynchus mykiss)] compared to the native species [inanga (Galaxias maculatus), redfin bully (Gobiomorphus huttoni) and common bully (Gobiomorphus cotidianus)]. Nonetheless, there was considerable variation between individual species, with rainbow trout outperforming common bully and juvenile inanga, but koi carp and rudd failing to pass any of the ramps. The differences in predicted probability of passage success between the native and exotic fish species in this study were sufficient in some cases to indicate the potential for the baffled fish ramps to operate as a selective migration barrier. Nonetheless, further testing is required to validate these results across a broader range of conditions before deployment.

An investigation of intraspecific habitat-related patterns of variation in oculoscapular lateral-line superficial neuromasts (SN) identified a decrease in the ratio of total SNs to pores, and a trend towards decreased asymmetry in SNs in the habitat-generalist common bully Gobiomorphus cotidianus from fluvial habitats compared to lacustrine habitats, suggesting habitat-related phenotypic variability. A greater ratio of pores to SNs, as well as less variation in the total number and asymmetry of SNs observed in the fluvial habitat-specialist redfin bully Gobiomorphus huttoni may provide further evidence of variations in the oculoscapular lateral-line morphology of fluvial habitat G. cotidianus individuals serving as adaptations to more turbulent environments.

A series of 14 day experiments was conducted on five common New Zealand fish species (redfin bully Gobiomorphus huttoni, inanga Galaxias maculatus, brown trout Salmo trutta, longfin eel Anguilla dieffenbachii and koaro Galaxias brevipinnis) to assess the effect of pH on survival and changes in body mass. No species survived in water of pH

This study evaluated the effect of ramp length and slope on fish passage over baffled ramps with 15° and 30° gradients. Three fish species indigenous to New Zealand were tested: the redfin bully Gobiomorphus huttoni, the common bully Gobiomorphus cotidianus and the inanga Galaxias maculatus with ramp lengths of 3, 4·5 and 6 m. As slope and ramp length increased, passage success rate decreased for G. maculatus and G. cotidianus. At a slope of 15°, both G. maculatus and G. cotidianus could pass all ramp lengths tested with the highest success rate on the 3 m ramp. As the gradient increased to 30°, G. maculatus could only pass the 3 m ramp, and G. cotidianus were incapable of passing any ramp. Gobiomorphus huttoni were the only test species capable of climbing the wetted margin of the ramps. Increasing ramp slope significantly reduced passage success for G. huttoni, but ramp length, up to the maximum used in this study, had no significant influence on successful passage.

Species termed 'habitat-generalists' are able to survive across a wide range of habitats, potentially enabled by the plastic behaviours and morphologies of individuals. This study aimed to compare habitat-related adaptive specialisation in habitat-generalists and specialists, by comparing feeding abilities of fish under varied hydrodynamic conditions. We compared the proportion of prey consumed by a New Zealand fluvial habitat- specialist, the redfin bully, to a closely related habitat-generalist found in fluvial and lacustrine habitats, the common bully, over a 6-h period in either still or turbulent aquaria. We tested for intraspecific habitat-specific adaptations by comparing feeding of common bullies from habitats with different hydrodynamic conditions. Within common bullies, previous research has documented a pattern of more lateral-line system oculoscapular canal pores in fluvial habitats compared to lacustrine ones. By testing for a relationship between total pores and feeding success, we also aimed to identify the adaptive value of an increase in pores in turbulence. We identified decreased feeding (i.e., proportion of prey consumed) by both species in turbulence, but less so for redfin bullies. There was no clear indication of adaptation to habitat type by common bullies, with high variability in feeding by fish from all locations. We also found no statistical relationship between feeding and total oculoscapular canal pores. The results of this study suggest specialised adaptations of a habitat-specialist to turbulent environments. The variability in feeding activity of common bullies also suggests the importance of behavioural plasticity in the survival of a habitat-generalist across a wide range of conditions.

This study uses Passive Integrated Transponder (PIT) technology to describe the habitat use patterns of the small, benthic redfin bully (Gobiomorphus huttoni). A 100-m reach of small upland stream in Manawatu, New Zealand was mapped to scale and inventoried for microhabitat variables. Flow velocity, depth, surface turbulence, substrate size and interstitial refuge space availability were measured in 0.25-m2 quadrats throughout the reach. A total of 67 redfin bullies were PIT tagged within the reach and monitored during day and night surveys in 2008 with a portable PIT monitoring system. Of these, 72 % were detected at least once and 64 % were detected 5 times or more within the study reach. Univariate analyses showed that redfin bullies utilized microhabitats that had larger substrate particles and more interstitial refuge spaces compared with all microhabitats available in the reach. During the day, redfin bullies were found in areas with larger substrates than areas where they were found at night. No differences in microhabitat use were found regarding gender, body size or season. Multivariate analysis revealed four macrohabitat types and showed that redfin bullies used deeper, complex macrohabitats during the day, then spread out to occupy all available macrohabitats at night. These findings have implications for river managers trying to cope with increasing anthropogenic impacts such as sedimentation.

Mahurangi Technical Institute (MTI) operates a commercial fish hatchery that conducts aquaculture research, acts as a teaching tool for aquaculture students, breeds native fish for reintroduction projects, and for supply to zoos and public aquariums for display, as well as breeding selected introduced species for biological control of aquatic weeds throughout New Zealand. This research arm has a long and successful history in the breeding and rearing of a number of fish species, including New Zealand native threatened freshwater-fish species. The Shortfin eel Anguilla australis, Giant kokopu Galaxias argenteus, Banded kokopu Galaxias fasciatus, Shortjaw kokopu Galaxias postvectis, Koaro Galaxias brevipinnis, Redfin bully Gobiomorphus huttoni, Common bully Gobiomorphus cotidianus, Giant bully Gobiomorphus gobioides, Cran's bully Gobiomorphus basalis, Freshwater shrimp Paratya curvirostris and Freshwater crab Amarinus lacustris have all been bred successfully at MTI. Of these native species, MTI has successfully closed the lifecycle of Giant kokopu, Banded kokopu, Cran's bully, Common bully, Freshwater shrimp and Freshwater crab. This paper focuses on work so far conducted to close the lifecycle of the Shortfin eel and the Giant kokopu.

SUMMARY 1. Within-species phenotypic variation is hugely variable and may play a role in determining the range of habitats a species can exploit. Our study addressed two main questions: 1. does phenotypic variation allow some species (i.e. habitat-generalists) to use heterogeneous habitats and 2. are habitat-generalists more variable than species occupying relatively homogeneous environments (i.e. habitat-specialists)? 2. We examined the morphology of the common bully (Gobiomorphus cotidianus), a habitatgeneralist eleotrid fish found in lakes and rivers throughout New Zealand. We also compared the level of morphological variability in common bullies with that in the closely related redfin bully (Gobiomorphus huttoni), a habitat-specialist of moderate- and fast-flowing rivers. 3. Common and redfin bullies were collected from the South Island of New Zealand. A series of body and fin measurements were made, and cephalic dorsal head pores of the mechanosensory lateral-line system were counted. The pores and associated canal neuromasts are important for prey detection and predator avoidance in other species, particularly, in turbulent conditions where the effectiveness of superficial neuromasts may be compromised. 4. The common bully had more dorsal head pores in fish from rivers than in those from lakes. This pattern was apparent only in adults, suggesting that selective pressures associated with adult habitat, be it rivers or lakes, are responsible. 5. As expected, there was greater phenotypic variability in the generalist common bully than in the specialist redfin bully, particularly with regard to the sensory pores, suggesting their importance for survival in turbulence. 6. We identified habitat-related patterns in phenotypic variability in a generalist species and demonstrated a link between phenotypic variability and habitat breadth. Variation in the common bully may explain its ability to occupy a range of habitats.

Common native fish species that are rare in New Zealand rivers with high suspended solids (SS) concentrations were identified to determine which species were likely to be most affected by high SS concentrations. Mortality rates for the three most sensitive species (banded kokopu Galaxias fasciatus, redfin bully Gobiomorphus huttoni, common smelt Retropinna retropinnd) were measured over a range of SS concentrations to identify lethal concentrations. The survival of banded kokopu and redfin bully was not reduced by SS concentrations up to 43 000 g m−3; however, the 24‐h survival of common smelt was reduced by SS concentrations over 1000 g m−3, and its median lethal concentration (LC50) was close to 3000 g m−3. SS concentrations over 3000 g m−3 for more than 24 h will therefore reduce smelt but not affect the mortality of most other common native fish species. Although mortality from high concentrations of SS can account for the scarcity of smelt in rivers with high SS concentrations, mortality fro...

The effects of surface type and slope on fish passage over artificial ramps were evaluated for two small diadromous fish species native to New Zealand: the redfin bully Gobiomorphus huttoni and adult and juvenile inanga Galaxias maculatus. Surfaces tested include smooth plastic, sand, gravel (limestone chips 5–20 mm), nylon brush and two plastic moulded cores of ground drainage products Cordrain® and Miradrain®. Slopes of 15° (1:3·7), 30° (1:1·7) and 45° (1:1) were assessed. Slope was the greatest factor influencing successful passage, with the lowest gradient tested (15°) providing the highest passage for both fish species. Most ramps at 45° only allowed the passage of redfin bullies, these fish being capable of ‘climbing’ the wetted margin of the ramps. Because of this climbing ability, redfin bullies were not as affected by the ramp surface, as inanga. Nevertheless, the smooth plastic surface, which resulted in the highest water velocities over the ramps, was un-passable by either species at slopes >15°. Gravel, the nylon brush and the two plastic moulds provided high passage rates for inanga at gradients of 15 and 30°. At a slope of 45°, Miradrain® was the only surface inanga could pass. Overall, Miradrain® produced the most successful passage for both inanga and redfin bullies, but to maximize passage, slope should not be >15° and a wetted margin is essential for climbing species.

The acute toxicity of un‐ionised ammonia to seven New Zealand indigenous fish and one indigenous crustacean species was established. Shrimp (Paratya curvirostris) was the most sensitive species, followed by banded kokopu (Galaxias fasciatus), common bully (Gobiomorphus cotidianus), common smelt (Retropinna retropinna), redfin bully (G. huttoni), inanga (Galaxias maculatus), and longfin and shortfin eels (Anguilla dieffenbachii and A. australis). The 96 h LC50 at 15°C and pH 7.5 and pH 8.1 ranged from 0.75 to 2.35 mg NH3 I−1 for these species. Unusually, New Zealand fish were more tolerant to ammonia than some native invertebrate species tested by a similar method. Within the limits of the life stages and species tested here, adequate protection is provided for native fish by adopting US Environmental Protection Agency ammonia criteria.