Response of Migrating Adult Salmonids to Vertical and Horizontal Rectangular Orifices at Two Depths

Publication Date



adult, Bonneville Dam, chinook, coho, horizontal, Oncorhynchus tshawytscha, orifices, salmon, salmonids, steelhead, trout, upstream migration

Report number

Fisheries No. 547

Publication place

Washington, D.C.


United States FIsh and Wildlife Service

Series Title

Special Scientific Report


The response of migrating adult salmonids to various placements of rectangular fishway orifices was studied at the Fisheries-Engineering Research Laboratory, on the Washington end of Bonneville Dam. Chinook salmon (Oncorhynchus tshawytscha), steelhead trout (Salmo gairdneri), and coho salmon (O. kisutch) approaching a vertical wall had the the alternatives of entering rectangular orifices positioned either horizontally or vertically and either shallow (3 feet) or deep (9 feet). The responses of the three species to the various orifice conditions are analyzed. More migrants passed through shallow orifices than deep orifices, and more salmonids entered vertical orifices than horizontal orifices.

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