Impoundment and introductions: Their impacts on native fish of the upper Waipori River, New Zealand

The distribution of fish species in tributaries of Lake Mahinerangi, a hydro electric storage impoundment, and its feeder catchment the upper Waipon River were surveyed Six fish species were located during the survey of 46 sites, ot which Galaxias species and brown trout were the most widely distributed Only single fish species were recorded at 35 sites (76 1%), two or more at eight sites (17 4%), and none at three sites (6 5%) Absent from all the survey sites was the long‐finned eel, the most ubiquitous native fish ot New Zealand The fish distributions and presence offish passage barriers suggest a dominance hierarchy existed with dominant species excluding other species from certain stream reaches Brown trout was considered the most dominant species, and koaro and brook char the next most dominant Two non‐migratory galaxnds, the dusky galaxias and Eldons galaxias, were considered the most susceptible to displacement and have probably suffered range contractions since the creation of Lake Mahinerangi and the introduction of salmonids

Keywords:

• Galaxias
• salmomds
• distribution
• threatened
• landlocked
• impoundment
• dominance
• species interaction
• community structure

Notes

National Institute of Water and Atmospheric Research, P O Box 11–115, Hamilton, New Zealand Email r allibone(aniwa eri nz