Reactions of Young Silver Salmon in Ten Velocity Combinations
behavior, salmon, silver salmon, swimming patterns, test flume
The reactions of 2,300 one-year-plus silver salmon (O. kisutch) were tested to various velocity combinations under conditions of light and dark. The following results were obtained. In 13 out of the 15 experimental conditions presented, significantly more fish were found in the areas of lower velocity. Fish did not retain their positions in areas of still water as readily as in areas of some velocity, except when the only alternative was water moving 1.69 fps. or more. In still water and at low velocities (up to approximately 1.0 fps.) the fish swam about in groups during the light trials. They seemed to be more influenced by the presence of other fish and observers than at higher velocities. The fish usually maintained positions in low velocity areas more readily when visual cues were present; however, velocity cues sufficed except in extreme cases. No significant preference was shown for up or downstream portions of the apparatus when both had closely equivalent velocities.