Behavioral Response of Walleye to a Bioacoustic Bubble Strobe Light Barrier

Walleye loss from Iowa reservoirs has recently been recognized as an important management issue.  We evaluated a nonphysical behavioral barrier for diverting walleye from a simulated outlet structure in a test facility.  The barrier system evaluated, produced a sound-bubble barrier, strobe light barrier, and a hybrid sound-bubble, strobe light barrier.  Trials were 16 h in duration.  Walleye escapement tended to be higher when lights were on compared to off, regardless of the level of sound.  The use of sound reduced walleye escapement compared to control conditions; however, all three sound frequency ranges tested produced similar levels of deterrence. Challenge rate was the number of times a walleye approached the barrier and was deflected and was lowest when lights remained off.  Trials evaluating the strobe light barrier demonstrated light provided no negative stimulus to walleye transition rate.  Overall, emigration probability was reduced by approximately 50% from control when the sound bubble barrier was operated alone and it look longer for fish to escape, suggesting a substantial reduction of walleye loss from reservoirs may be obtained by using a sound-bubble barrier without the use of strobe lights.