Laboratory Evaluation of the Survival of Fish Impinged on Modified Traveling Water Screens

Traveling water screens (TWSs) modified for fish protection can be used at power plant cooling water intakes to reduce the injury to and mortality of impinged fish. Existing biological efficacy data show that postimpingement survival is highly variable by species and has improved over time as screen designs have incorporated more fish-friendly features. Data with the improved screen designs were largely absent for many freshwater species prior to this evaluation. The mortality, injury, and scale loss rates of 10 species of freshwater fish impinged and recovered with a modified Ristroph-style TWS were evaluated in a laboratory flume. Fish were impinged at a 0.3-, 0.6-, or 0.9-m/s approach velocity. Over 13,000 fish were tested in more than 100 replicates during the study. Mortality rates did not exceed 5% for any species and velocity tested. Despite a general trend toward increasing mortality at higher velocities, velocity was only a significant factor in the mortality of Bluegills Lepomis macrochirus . Injury and scale loss rates were low for most of the species tested, although they were more variable than the observed rates of mortality. There was a trend toward lower mortality, injury, and scale loss in larger fish. In all cases in which fish length was a significant factor, the pattern of decreasing mortality, injury, and scale loss as fish increased in length was consistently observed. These results indicate that TWSs modified for fish protection have the potential to prevent impingement losses at power plant intakes. Received June 28, 2013; accepted October 25, 2013