Assessing the deterrence effect of target-specific acoustic startle technology on killer whales and humpback whales during interactions with Norwegian purse seine herring fishery

Abstract

Norwegian fishers report an increase in negative interactions with marine mammals: An issue that is also on the rise, globally. Efforts to mitigate these interactions using currently available methods have yielded little success for larger cetaceans. This study examines the efficacy of a novel target-specific acoustic startle technology (TAST) in deterring killer whales (Orcinus orca) and humpback whales (Megaptera novaeangliae) during interactions with purse seine fisheries for Norwegian spring-spawning herring (Clupea harengus) in Northern Norway. This was done by conducting controlled exposure playback experiments in proximity of fishing vessels and feeding whales and recording the presence of the whales before, during and after the acoustic playbacks. The results suggest that TAST may be effective in reducing the likelihood of negative killer whale interactions with the fishery, but on the effect was much less clear in terms of humpback whale behavior. Overall, the expected number of surfacings of killer whales was reduced by 85% during exposure to TAST, with no evidence of habituation. Additionally, the effect of TAST appears to attenuate quickly over distance with a strong recovery (return of whales) during the post-exposure observation phase, which is positive for preventing harm due to long-term habitat avoidance. This thesis provides strong indications that TAST can be used as a safe and effective tool for mitigating whale-fisheries conflicts in the marine environment.