Survival of Juvenile Rainbow Trout Passing through a Francis Turbine

Abstract

The immediate survival rate of juvenile rainbow trout Oncorhynchus mykiss (fork length, 81 ± 1 mm) that passed through a Francis turbine at Hb Dam on the Hinemaiaia River in the central North Island of New Zealand was estimated at 95.6 ± 1.1% (mean ± SE). The survival rate decreased to 93.1 ± 1.4% after 24 h and remained unchanged after 96 h. The survival rate was derived using maximum likelihood estimators for a tag–recapture model involving three releases of 200 fish of similar average length, and the mortality due to handling was estimated using a control of 200 similarly sized fish. The high survival of juvenile rainbow trout (<80 mm) passing through the Francis turbine at Hb power station provides a safe route for fish migrating downstream from Hb Lake into the Hinemaiaia River and Lake Taupo.