A complex sound coupled with an air curtain blocks invasive carp passage without habituation in a laboratory flume

Invasive bigheaded carp are currently advancing upstream in the Mississippi River and threaten to invade its headwaters. The possibility that sound projected into navigation locks might block this invasion is being considered and four types of complex sound have been shown to have promise: an outboard-motor sound, a proprietary cyclic sound, air curtains, and the (coupling) pairing of this proprietary sound with an air curtain. In a laboratory study, we systematically tested the effects of these stimuli on invasive bighead carp and common carp, as well as the native largemouth bass (which lack hearing specializations), in a darkened laboratory flume. We were specifically interested in whether the outboard-motor sound or the proprietary sound might be more effective at blocking and deterring fishes (i.e., does the type of complex sound matter), and whether coupling either of these sounds with an air curtain might enhance their effectiveness. We found that the proprietary sound was more effective than the outboard-motor sound at both deterring and blocking common carp as well as deterring bighead carp. The largemouth bass were less affected by both sounds. We also found that when an air curtain was coupled to either sound, the combined stimulus became more effective at blocking all three species. This was especially true for the proprietary sound which when coupled with an air curtain blocked 97% of bighead carp. The proprietary sound coupled with the air curtain has promise to block bigheaded carp and should be considered for field tests.