How fish detect screens: Investigating fishes' abilities to avoid screens while swimming in a current, and testing vibrations and strobe lights as deterrents

The importance of vision and the lateral-line system in fish-screen and louver avoidance was investigated in marine and freshwater species, including shiner surfperch (Cymatogaster aggregata), staghorn sculpin (Leptocottus armatus), steelhead trout ( Oncorhynchus mykiss), Chinook salmon (Oncorhynchus tshawytscha ) and Sacramento splittail (Pogonichthys macrolepidotus). Fish were viewed swimming in front of screens and louvers in laboratory flumes. Experiments were conducted during the day (lighted) and night (dark, to limit vision). Streptomycin-sulfate treatments were used to block fish's lateral-line systems. The fish's lateral-line system was treated with the vital stain stained with 2-(4-(dimethylamino)styryl)-N-ethylpyridinium iodide (DASPEI) and viewed under a stereofluorescent microscope to verify the streptomycin treatment's effectiveness. Industrial vibrators and a strobe light directed at the screens and louvers were tested as possible behavioral deterrents. The total number of times a fish contacted the screens or louvers was analyzed as a measure of performance. All species tested contacted the screens significantly more often during the night. The response to the streptomycin, vibration and strobe-light treatments varied among species. More fish passed through the louvers than became impinged on the screens. Juvenile Chinook salmon passed through the louvers more frequently during the night and when swimming in faster currents. This research should benefit fisheries and water resources managers, regarding their-fish protection decisions. It also poses important questions for future research.