Northwest Fisheries Science Center

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Document Type: Contract Report
Center: NWFSC
Document ID: 6770
Title: An assessment of the relationship between smolt development and fish guidance efficiency at Bonneville Dam
Author/Editor: Albert E. Giorgi, Waldo S. Zaugg, Brian R. Beckman
Publication Year: 1989
Publisher: National Marine Fisheries Service
Contracting Agency: U.S. Army Corps of Engineers. Portland, Oregon
Contract Number: DACW57-87-F -0320
Pages: 35
Date: May 1989

Research conducted by the National Marine Fisheries Service (NMFS) in cooperation with the U.S. Army Corps of Engineers (COE) has demonstrated that fish guidance efficiency (FGE) not only changes from year to year and among dams, but can also change during the course of any year's outmigration and even within a day.  Of juvenile salmonids entering a turbine intake, FGE is the proportion that are guided into the gatewells and accompanying bypass system. 

Data acquired at Lower Granite and Little Goose Dams from 1985 to 1987 suggest that intraseasonal changes in FGE are associated with the changing physiological status of the smolt population.  NMFS researchers have presented evidence which indicates that yearling chinook salmon, Oncorhynchus tshawytscha, that are fully smolted within the population are more susceptible to guidance by traveling screens.  We hypothesize that over the course of the outmigration the proportion of fully smolted fish in the population increases, which in turn explains intraseasonal increases in FGE observed at Lower Granite Dam. 

Since 1983, NMFS has been conducting research at Bonneville Dam to evaluate and improve FGE at the Second Powerhouse.  Results have often been disappointing despite many structural modifications to the collection system.  One factor that may be influencing these results is the extent to which the physiological status of the smolt population changes during the outmigration.  The purpose of this study is to determine if seasonal changes in the physiological status of the migrant population are evident at Bonneville Dam, and assess whether those changes are related to concurrent FGE estimates.