Effect of Water Velocity on the Fish-Guiding Efficiency of an Electrical Guiding System

The study was performed in 1962 in a diversion of the Yakima River near Prosser, Wash. Massive structures for regulating the water velocity, producing the desired electrical field, and collecting the guided fish were installed. Evaluation facilities consisted of rotary drum screens to divert all fish that escaped past the electrical field to an inclined-screen trap. The fish tested were wild, downstream-migrating fingerlings of chinook salmon, Oncorhynchus tshawytscha; coho salmon O. kisutch; and rainbow or steelhead trout, Salmo gairdneri. The variables were three water velocities, three species, and four test periods. Fish-guiding efficiency tended to decrease with increasing water velocity. The guiding efficiencies of the electrical system at water velocities of 0.2, 0.5, and 0.8 (m.p.s) meter per second were, respectively, 84.2, 54.2, and 50.2 percent for chinook salmon, 82.4, 47.8, and 42.8 percent for coho salmon; and 69.9, 40.2, and 44.8 percent for rainbow or steelhead trout. The guiding efficiency achieved was, thus, highest with chinook salmon, intermediate with coho salmon, and generally lowest with rainbow or steelhead trout. The use of electricity to guide juvenile salmon and trout migrating downstream may be feasible in certain environments where the water velocity does not exceed 0.3 m.p.s. but does not appear practical for use in most rivers and streams.