Response of Migrating Adult Salmonids to Vertical and Horizontal Rectangular Orifices at Two Depths
adult, Bonneville Dam, chinook, coho, horizontal, Oncorhynchus tshawytscha, orifices, salmon, salmonids, steelhead, trout, upstream migration
Fisheries No. 547
United States FIsh and Wildlife Service
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.