The Influence of a Power Dam in Modifying Conditions Affecting the Migration of the Salmon

Abstract

At stream junctions and in selecting a spawning ground, migrating salmon prefer the colder water. Power dams modify conspicuously current and temp. conditions in the stream. In the case studied (Baker River), the migrating salmon tend to enter the cold tailrace rather than the fish-ladder. When later they try the latter, many are too exhausted to surmount it. Of those which were lifted over the dam only about 1/3 reached the normal spawning grounds some miles above the reservoir created by the dam. Some were certainly physically incapacitated for the trip; others were probably trapped by the deep cold water in the reservoir, where, if they spawned, the eggs probably perished during the fluctuations in water level.