Assessing the use of vibrations and strobe lights at fish screens as enhanced deterrents for two estuarine fishes.

The role of vision and the lateral-line system in fish-screen avoidance behaviours was investigated in shiner surfperch Cymatogaster aggregata and staghorn sculpin Leptocottus armatus. Avoidance experiments were conducted in front of water-diversion-type wedge-wire fish screens in a laboratory flume with a 0.3 m s water velocity. Fish contacted the screens less frequently during the day than night, indicating that fish screen avoidance is visually mediated during the day. Input from the fishes' lateral-line systems was also blocked with streptomycin-sulphate treatments during the night to determine if these fishes use mechanoreceptive cues to guide screen avoidance in darkened conditions. Streptomycin-treated and untreated fish had similar contact rates suggesting that mechanoreceptive guidance was not increasing the fishes' abilities to avoid contact with non-vibrating screens at night. Fishes were stained with 2-(4-(dimethylamino)styryl)-N-ethylpyridinium iodide (DASPEI) to assess the streptomycin treatment's effectiveness. We also tested the fishes' ability to avoid contact with the screens at night, when a strobe light or industrial vibrator was operated on the screens, to respectively increase the screen's visual and mechanoreceptory guidance potential. Cymatogaster aggregata contacted the screens significantly less frequently when they were vibrating, compared with their night-time controls, suggesting useful mechanoreceptive guidance. Leptocottus armatus contacted the screens significantly less frequently under strobe-light illumination, compared with their night-time controls, suggesting useful visual guidance. This research should benefit fishery and water-resource managers, regarding the development of future fish-protection decisions at screened water diversions.