Masters Defense

Acoustically conditioned bigheaded carp deter naïve fish from upstream passage 

Broadband sound and CO2 are non-physical deterrents which show potential for restricting upstream migration of invasive silver (Hypophthalmichthys molitrix) and bighead carp (H. nobilis). A multimodal deterrent combining broadband sound and dissolved CO2 proved 100% effective at deterring upstream passage in a model lock and dam for conditioned bighead or silver carp schools, including food motivated fishes. While lock chambers provide strategic bottlenecks to deploy this deterrent, not all fish in the area may experience conditioning and new fish may arrive between treatments. To assess the efficacy of this deterrent under field conditions, this study examined if conditioned fish could influence the swimming behavior of naïve fish in schools. Bigheaded carp were trained to move upstream through a lock chamber to receive food in a 10,000 L model lock and dam. Three of the ten fish in each school underwent carbon dioxide and acoustical conditioning. The mixed schools underwent 28 sound-only trials over the course of a week, with 98.8% of these fish deterred (one naïve fish passed through the lock). In comparison, 80% of the bigheaded carp in naïve schools passed through the acoustic deterrent. Thus, a minority of conditioned fish can influence naïve fish which would greatly improve effectiveness of acoustic deterrents under standard lock operations. These results support the use of multimodal deterrents to prevent upstream migration of bigheaded carp.