Strategies to deter Pacific Herring from aquatic farm infrastructure

Objective Seaweed aquaculture can benefit coastal ecosystems through the provisioning of new habitat. However, not all aquaculture–ecosystem interactions are created equal: Some interactions can result in substantial crop loss and potentially reduce the fitness of wild organisms, as is the case with Pacific Herring Clupea pallasii spawning on kelp farms in Alaska. This study drew upon herring physiology and ecology to identify potential nonlethal methods that aquatic farmers could implement to deter herring from aquaculture infrastructure while also minimizing impacts to marine mammals. Methods We exposed Pacific Herring to various stimuli (bubbles, active acoustics, lights, and suspended objects) in a net-pen and tracked fish movement using a Kongsberg-Mesotech Flexview multibeam sonar. The difference in the distance of individual fish from the stimulus when it was on and off was analyzed using linear mixed-effects models, and the effect size of each treatment was determined by calculating Cohen’s d. Results Across the methods tested, only bubble curtains elicited a clear behavioral response in Pacific Herring Clupea pallasii based on the effect size of the treatment. Acoustic pingers and strobing lights had no effect on the location of herring in the experimental space, while suspended moving or stationary fishing flashers either had no effect or attracted herring. Conclusions Although Pacific Herring demonstrated a behavioral response and avoidance of bubble curtains, deploying this technology at remote farm sites will be a challenge. Further research into developing low-cost strategies to minimize negative interactions between aquaculture and wild organisms is necessary for the sustainable growth of the industry.