Redfin bully

Abstract: One hundred and thirty individual fish were collected and passive integrated transponder (PIT) tagged in a 100-m reach of a small North Island, New Zealand stream. The positions of the fish were monitored with a hand-held portable PIT antenna over 41 occasions during day and night in 2008/2009. Redfin bully (Gobiomorphus huttoni), shortjaw kokopu (Galaxias postvectis) and koaro (Galaxias brevipinnis) were the most represented and commonly detected species (75%, 73% and 83% detection rates, respectively). Nine longfin eels (Anguilla dieffenbachii) were tagged but only two were later detected. Redfin bullies with lower condition factors than conspecifics were less likely to be detected following tag implantation. Shortjaw kokopu were less likely to be detected but more retained tags than redfins and koaro. No difference in tag detection rates was found over a range of flow levels, nor between surveying during day and night, although a small decline in detection rates occurred as water temperature d...

Abstract: 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.

Abstract: 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...

Abstract: 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 <4 although there was 100% survival of all adults at pH 4.5, G. maculatus larvae were also tested and had high mortality at this pH. Results suggest that adults are tolerant of low-pH waters; however, successful remediation of anthropogenically acidified streams will require an understanding of the susceptibility to low pH on different life cycle stages.