Abstract
Abstract Subyearling (age-0) hatchery summer-run Chinook Salmon Oncorhynchus tshawytscha have been released into the Columbia River in mid-June from Wells Fish Hatchery, Washington, since 1993, but release-to-adult survival (SAR) under this strategy has been low. I used paired releases of four broods of coded-wire-tagged age-0 Chinook Salmon released in mid-May (early release [ER] group) and mid-June (late release [LR] group) to evaluate whether advancing the release date could improve SAR. Additionally, passive integrated transponder tags implanted in a subsample of each release group were used to estimate emigration rate and release-to-McNary Dam survival of juvenile fish. Mean migration rate from release to McNary Dam was significantly faster for LR fish than for ER fish. No among-year difference in mean survival from release to McNary Dam was observed between ER and LR groups, although differences were observed within years. Mean overall SAR was significantly greater for ER fish than for LR fish. These results suggest that altering the release date of age-0 Chinook Salmon at Wells Hatchery would enhance return survival.
Published Version
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