Abstract
Abstract Passage of upstream migrant sockeye salmon (Oncorhynchus nerka) and chinook salmon (O. tshawytscha) through the three pool-and-weir type fish ladders at Rock Island Dam on the Columbia River was controlled to a large extent by the proportion of the total flow discharged through the turbines and also by the location of the open spillway gates with respect to the ladders. At intermediate river discharges (140,000 through 300,000 ft3/sec) it was demonstrated conclusively that the fish's preference for either the right or center ladders could be controlled by spilling adjacent to these ladders. Response to the attraction spill was rapid. Attraction of sockeye was dependent not only upon spill position but also upon the tailwater elevation at the ladder entrance. The statistical analysis of fish behavior in an experimental choice situation is discussed in some detail, particularly the use of Chi-square and analysis of variance methods.
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