The Swimming Ability of Immature Silver Salmon (Oncorhynchus kisutch) Measured in an Experimental Flume
barriers, downstream fish passage, fatigue, flume, illumination, inclined screen, intake, salmon, screens, silver salmon, swimming, swimming ability
The swimming ability of immature silver salmon was measured by two methods: a) The time before the fish became impinged upon a stationary vertical screen. This method is the better measure of severe fatigue under strong motivation. An average of 35 percent of the fish were still swimming after 15 hours of continuous exposure to nominal velocity of 3.4 fps. b) The time before displacement over an inclined plane at the end of the flume. This method may be as much a measure of motivation as of physical fatigue. All fish were displaced 24 feet downstream in less than 15 minutes with nominal velocity of 3.9 fps. The velocity at different points in the flume varied widely depending upon how the water was introduced from the intake towers. The fish that were impinged in the first 15 minutes were significantly smaller than those still swimming at the end of 15 hours. When a 20 degree angled light barrier with 90 ft. cdls. of illumination was introduced in one half of the flume, 80 percent of the fish were able to avoid this side and were impinged on the retaining screen or were displaced over the falls in the dark.