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The Problem Fall chinook salmon (Oncorhynchus tshawytscha) in the Snake River are currently listed as threatened under the Endangered Species Act (ESA). Although fish bypass systems reduce the mortality of fish entering turbine intakes at mainstem hydroelectric dams, they are only operated during the spring, summer, and early fall during the peaks of seaward migrations of juvenile fish. Some juvenile fall chinook salmon are known to holdover in Lower Granite Reservoir on the Snake River during the winter and resume seaward migration the following spring. However, with fish bypass facilities inoperable during the winter, it is unknown whether late migrating fall chinook salmon are passing Lower Granite Dam during the winter months. If so, the only route of passage would be via turbines and mortality would be increased for this ESA-listed stock. Objectives This study will use acoustic telemetry to determine where holdover fish overwinter in Lower Granite Reservoir and if, and when, fish pass Lower Granite Dam during the winter months when the bypass system is shut down. Methodology
Acoustic telemetry will be used to document juvenile fall chinook salmon passage past Lower Granite Dam in the winter and habitat use in Lower Granite Reservoir. Fish will be captured by hook-and-line sampling and will be implanted periodically with acoustic transmitters. An acoustic receiver will collect data on fish passing Lower Granite Dam via eight hydrophones of which four will be located in the forebay and four will be located in the tailrace of the dam. In addition to this fixed detection array, tagged fish will be periodically tracked by boat using a mobile tracking receiver and two hydrophones to determine where tagged fish reside in Lower Granite Reservoir. Data will be analyzed for passage timing past the dam and for reservoir movement behavior. Highlights and Key Findings This is a new study, which began in early 2003. There are no results to report at this time. Where Are We Headed In 2003 This study will continue in the fall of 2003. A technical report summarizing our results will be published in the fall of 2003. Project Contact Kenneth Tiffan Email: ken_tiffan@usgs.gov Publications |
