Survival of Juvenile Salmonids Passing through Bypass Systems, Turbines, and Spillways with and without Flow Deflectors at Snake River Dams

Abstract

Abstract Using yearling chinook salmon Oncorhynchus tshawytscha and steelhead O. mykiss tagged with passive integrated transponders (PITs), we estimated passage survival through bypass systems, turbines, and spill bays with and without flow deflectors at Snake River dams relative to survival of fish released into the tailrace below the dam. Actively migrating fish were collected and marked with PIT tags at Snake River dam smolt collection facilities. Groups of tagged fish were then released through hoses into different passage routes; releases were coincident with a tailrace release approximately 1–2 km below the dam. Relative survival was estimated by the use of tag–recapture models for paired releases from detections of individual PIT-tagged fish at juvenile collection or detection facilities at downstream dams. Detection sites included Little Goose, Lower Monumental, McNary, John Day, and Bonneville dams, depending on the release location and year. Standard errors of relative survival probability estim...