Document Type

Thesis

Date of Degree Completion

Fall 2015

Degree Name

Master of Science (MS)

Department

Biology

Committee Chair

Dr. Clay Arango

Second Committee Member

Dr. Alison Scoville

Third Committee Member

Dr. Clay Arango

Fourth Committee Member

NA

Abstract

Columbia River hydropower is an economic mainstay of the Pacific Northwest. However, it is well known that the construction of hydropower dams has added anthropogenic pressure to Columbia River salmon populations. Juvenile salmon that pass through powerhouse turbines at large hydropower dams display higher mortality rates than salmon passing through alternative routes; thus at Priest Rapids Dam, a top-spill fish bypass was constructed as a safer alternate downstream passage. To investigate the efficacy of this new passage structure, an acoustic telemetry study was conducted in the spring of 2014 to determine the ability of the bypass to collect and safely pass juvenile steelhead and Chinook salmon. The bypass collected 47% of the monitored steelhead and 38% of the monitored yearling Chinook salmon. Analysis of route choice identified forebay temperature, powerhouse discharge, spillway discharge and forebay approach patterns as significant drivers of passage selection. Immediately following dam passage, steelhead and Chinook salmon that used the bypass had higher survival and migrated faster compared to powerhouse route fish. The Priest Rapids Fish Bypass served its intended purpose by reducing the anthropogenic footprint of this hydroelectric facility on migrating juvenile salmon, which will aid the potential recovery of Columbia River salmon.

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