TURBINE PASSAGE SURVIVAL ESTIMATION FOR CHINOOK SALMON SMELTS (ONCORHYNCHUS-TSHAWYTSCHA) AT A LARGE DAM ON THE COLUMBIA RIVER

The short-term survival rate of hatchery-reared fall yearling chinook salmon smelts (On,corhynchus tshawytscha) introduced at 3.1 m below th e turbine intake ceiling (N = 350) at a large Columbia River hydroelec tric dam relative to the survival. rate of controls (released in the d ischarge) was estimated at 93.0% (90% profile CI = 90.1-95.5%); among those introduced at 9.3 m depth (N = 250) the survival rate was 94.7% (90% CI = 91.9-97.0%). Differences were not significant, and the poole d estimate of 93.9% (90% CI = 91.9-95.7%) is higher than is generally assumed or reported (70-89%) for salmonids. Unlike the prevailing mode ls based on recovery ratios of alive fish only, our likelihood model i ncluded the capture probabilities of both the alive and dead fish for estimation of parameters and their standard errors. Survival rates rep orted herein refer to the direct effects of turbine passage; those rep orted in the literature, however, do not make a clear distinction betw een direct (immediately upon turbine passage) and indirect effects tha t may occur over time. The types of fatal injuries observed suggested that a reduction or elimination of gaps between the hub and runner bla des may enhance fish survival.