Responses to pH of nine fishes and one shrimp native to New Zealand freshwaters

Abstract

The pH values preferred and avoided by adult stages of inanga (Galaxias maculatus), common bully (Gobiomorphus cotidianus), common smelt (Retropinna retropinna), and redfinned bully (G. huttoni), were determined in a gradient tank (pH ranges of 3.2–11.2). Juvenile stages of inanga, common bully, shortjawed kokopu (Galaxias postvectus), koaro (G. brevipinnis), banded kokopu (G. fasciatus), shortfinned (Anguilla australis) and longfinned (A. dieffenbachii) elvers and glass eels, as well as freshwater shrimp (Paratya curvirostris) were also tested. Most species were found to have pH preferences and all except inanga avoided pH values of above c. 9.5. Adult fish showed stronger preferences than juveniles. An avoidance of pH values below 6.5 was apparent in most species except shortfinned elvers, koaro, and banded kokopu. Results indicate that the range of pH encountered in lowland streams are unlikely to have a major impact on the distribution of most New Zealand native freshwater fish.

Keywords:

• pH gradient
• native freshwater fish
• pH preference
• pH avoidance
• acid
• alkali
• Galaxias maculatus
• G. postvectus
• G. brevipinnis
• G. fasciatus
• Gobiomorphus cotidianus
• G. huttoni
• Retropinna retropinna
• Anguilla australis
• A. dieffenbachii
• Paratya curvirostris