Acoustic and multimodal deterrents to limit invasive fish passage

Acoustic deterrents have been deployed with variable success to decrease fish interactions with anthropogenic hazards (i.e., power plant intakes, spillways) and prevent the spread of invasive species. Acoustic deterrents are nonphysical barriers that offer many advantages in that sound can travel a great distance, are relatively independent of light and weather conditions, do not interfere with navigation and are relatively inexpensive to implement. Assessing the efficacy of deterrents is challenging as there are few controlled or long-term studies and many reports fail to specify sound parameters (i.e., intensity, frequency) preventing independent assessment. It is imperative to factor fish sensory physiology when designing nonphysical deterrents as fish need to detect, localize and move away from the stimulus. The auditory sensitivity of the target species must be identified to optimize the acoustic stimulus and the ambient soundscape mapped to ensure the sound intensity will be effective. Animals may habituate to an aversive stimulus and therefore multimodal deterrents may prove more effective than single modal systems. This paper will provide an overview of acoustic deterrents, species targeted and their efficacy. Special emphasis will be given to efforts to block the upstream migration of invasive bigheaded carp in the Mississippi River basin that currently threatens the Laurentian Great Lakes. Recent studies using a multimodal acoustic deterrent that conditions fish to associate sound with carbon dioxide will be described.