| Summary: | Rebounding pinniped populations have led to renewed conflicts with fisheries over access to commercially important prey species. Non-lethal management tools, such as acoustic deterrent devices (ADDs), are commonly used to mitigate predation and aid the recovery of depleted fish stocks. However, most ADDs utilize painful sound signals, which can lead to hearing loss, habituation, and injury to non-target species. Alternatively, a new startle reflex-based ADD called TAST (Targeted Acoustic Startle Technology) has been shown to decrease pinniped predation with no adverse impacts on non-target marine species. Initial research on TAST deployment shows no evidence of target species habituation; however, the long-term effects of TAST on the predation success of individual pinnipeds is unknown. In the Salish Sea, harbor seal (Phoca vitulina) populations have rebounded since the early 1970’s and are suspected of impeding the recovery of Pacific salmon (Oncorhynchus spp.), a taxon of great ecological, cultural, and conservation concern. Harbor seals prey on adult salmonids returning to Whatcom Creek in Bellingham, WA, and have been studied since 2011. In the fall of 2020, TAST was deployed near the Whatcom Creek Hatchery fish ladder to deter harbor seal predation during the fall Chum (O. keta) and Chinook (O. tshawytscha) salmon runs. Based on observations and photographs, we assessed the long-term effectiveness of TAST by comparing the occurrence and foraging success of individual harbor seals in years before, during, and after TAST was deployed. Generalized Linear Mixed-Effects Models were used to determine how individual foraging success was impacted by TAST presence. This research will inform the effectiveness of novel pinniped predation management tools designed to encourage the recovery of depleted salmonid stocks.
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