The Effectiveness of Constant and Intermittently Flashing Light Barriers in Guiding Young Silver Salmon
barriers, channel, constant light, design, flashing light, flume, guidance, illumination, light conditions, salmon, silver salmon, swimming, swimming time, University of Washington
Using a 40 ft. cdl. light barrier set at an angle of 20 degrees to the direction of a 2 fps. flow of water, it was possible to guide statistically significant numbers of fish released from the right side across three-fourths the width of an experimental flume to a channel on the left side. There were six light conditions, with eight balanced replications of groups of 25 native fish per condition in the formal experimental design. Holding the peak level of illumination constant, the average swimming time in the flume was positively related to the 'on time' of the lights, with darkness at the bottom extreme and constant light at the other. In a series of supplementary tests, the number of fish which were still swimming at the end of the test was positively related to the peak level of constant illumination of the guiding barrier, with brighter lights associated with longer swimming times.