WRS MS Defense

TITLE: Evaluating CO 2 and sound as an invasive bigheaded carp deterrent in a model lock and dam

Bighead (Hypophthalmichthys nobilis) and silver (H. molitrix) carp, collectively referred to as bigheaded carp, are aquatic invasive fish that present a significant ecological threat to freshwater ecosystems across the United States. The continued upstream dispersal of bigheaded carp raises concerns about their potential establishment in habitats across the Upper Mississippi River and the Laurentian Great Lakes. Dams, along with their adjoining lock chambers, present potential strategic bottlenecks for restricting the movement of bigheaded carp within the Mississippi River and its tributaries. The development of a multimodal system incorporating bioacoustics and carbon dioxide (CO 2 ) has shown promise to act as an effective non-physical deterrent against the upstream passage of bigheaded carp through locks.

The effects of CO 2 injection paired with broadband sound (recorded from a 100hp outboard motor) were examined as a potential deterrent in a 10,000-liter model lock and dam system. During experimental trials (n=8), schools of 10 bigheaded carp were allowed to acclimate in the lock and dam tank over a period of 72-hours. Schools were then conditioned over two days to associate broadband sound (0.06-10 kHz; 145-150 dB re 1 Pa) with the simultaneous injection of CO 2 (~38,000 atm) within the lock chamber. Following conditioning trials, four broadband sound deterrent trials were conducted daily during a one-week period. During the acclimation, conditioning, and deterrent trials, fish behavior was evaluated using overhead video. Conditioned fish avoided the lock chamber whenever the broadband sound was active and the downstream gate was opened, effectively preventing upstream migration via the lock chamber. Carp showed no evidence of habituating to the broadband sound deterrent during week-long trials. Subsequent trials (n=8) evaluated the efficacy of the multimodal deterrent against bigheaded carp schools with a food-driven motivation to transit upstream despite acoustic deterrence. However, deterrent efficacy was maintained against food-motivated carp during the sound trial period. These results highlight the potential of using a multimodal stimulus to deter the upstream movement of bigheaded carp through lock chambers and provide an integrated strategy to protect threatened aquatic ecosystems from invasion.