|Document Type:||Journal Article|
|Title:||A review of flow and survival relationships for spring and summer chinook salmon Oncorhynchus tshawytscha from the Snake River Basin|
|Author:||John G. Williams, Gene M. Matthews|
A flow and survival relationship, based on 1970s research, for juvenile chinook salmon, Oncorhynchus tshawytscha, that migrate through the Snake and Columbia Rivers is the foundation of many fishery managers' recommendations for modifications to the hydropower system to stem the decline of populations recently listed under the Endangered Species Act. However, a review of the 1970s data found that estimated fish survivals through the hydropower system reflected conditions that no longer exist and that between 1977 and 1979 these estimated survivals were negatively biased. Debris entrained in front of, and throughout, the fish collection system of the uppermost dam on the Snake River resulted in fish descaling and most likely poor fish survival. Under the lowest flow conditions, decreased survival due to increased travel time was exacerbated by sporadic or less than optimal turbine operations, or both, which further delayed fish passage through the dams and, at the uppermost dam, subjected fish to debris for longer periods of time. Use of flow and survival relationships based on yearly estimates of juvenile migrant survival in the 1970's will probably not accurately predict survival of spring–migrating juvenile chinook salmon under present conditions. This is particularly true for survival predictions during low–flow conditions.