Evaluating CO₂ and sound as an invasive bigheaded carp deterrent in a model lock and dam

Several deterrents are currently being investigated to block the upstream migration of invasive silver (Hypophthalmichthys molitrix) and bighead carp (H. nobilis). Broadband sound (100 hp outboard boat motor recording) and dissolved CO₂ both show potential for restricting the upstream movement of invasive bigheaded carp through contained environments such as lock chambers. This study examined the effect of combining both broadband sound and CO₂ into a multimodal deterrent to restrict upstream passage via the lock chamber in a 10,000 L flow through model lock and dam system. Bigheaded carp schools were classically conditioned to associate broadband sound with elevated levels of CO₂ in the lock chamber. After conditioning, broadband sound alone was 100 % effective in restricting the upstream passage of bigheaded carp under standard lock chamber operations, and bigheaded carp were deterred from entering and transiting the lock chamber for 28 consecutive trials over a one-week period. These results could help inform field deployments of non-physical deterrents within lock chambers for restricting the upstream movement of invasive bigheaded carp.