Abstract
Abstract In June 1995, we evaluated the effectiveness of a 122-m-long array of 25 low-frequency transducers for guiding juvenile salmon away from turbine units 9 and 10 at Powerhouse I of Bonneville Dam, Columbia River, Oregon. Juvenile salmonids included subyearling and yearling chinook salmon Oncorhynchus tshawytscha and yearling coho salmon O. kisutch, steelhead O. mykiss, and sockeye salmon O. nerka. Generated sounds were predominated by 300-Hz and 400-Hz frequencies and transmitted as 2-s crescendos, with repeated amplitude ramps from 0 to about 160 decibels referenced to 1 μPa at 1 m every 2 s. Sound-on and sound-off treatments did not differ significantly in the mean number of fish passing north or south across the upstream end of the array, where the angle of incidence of flow was only about 5 degrees. The power of these one-tailed t-tests (α = 0.05) for detecting 50% differences in means was 82% for fish passing north across the array and 99% for fish passing to the south. We also counted smolts ...
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