The Use of a Chain Barrier to Guide Young Salmon
barriers, chains, channel, downstream fish passage, downstream migration, illumination, migration, night, salmon, University of Washington
Three age groups and four species of salmonidae (568 fish) were tested in a simple discrimination apparatus during the daytime and at night to determine the response to a chain barrier hung in still water. When the strands of safety chain were not more than 2.5 cm. apart, there was a statistically significant reduction in the number of fish entering either of the experimental channels, but the proportion of fish diverted (66 percent) was not considered large enough to be of practical importance. In the dark the chain barrier deflected only 56 percent of the fish, certainly not enough to be of value if the downstream migration occurs principally at night. The experimental alley with the slightly higher level of illumination deflected 89 percent of the fish in the daytime.