The effect of Targeted Acoustic Startle Technology on the foraging success of individual harbor seals

• Main Author: McKeegan, Kathleen Anne
• Format: Text
• Language: English
• Published: Western CEDAR 2022
• Subjects: harbor seal; Pacific salmon; pinniped management; acoustic deterrents; management tools; hazing devices; conservation conflict; Biology; Keta; Pacific; Phoca vitulina
• Online Access: https://cedar.wwu.edu/wwuet/1128; https://cedar.wwu.edu/cgi/viewcontent.cgi?article=2164&context=wwuet

Rebounding pinniped populations have led to conflicts with fisheries over commercially important prey species. Acoustic deterrent devices (ADDs) are used to aid the recovery of depleted fish stocks by mitigating pinniped predation. However, most ADDs use painful sound signals, which can lead to hearing loss and habituation. Alternatively, a new ADD called Targeted Acoustic Startle Technology (TAST) decreases pinniped predation with no evidence of harm or habituation, but effects on the foraging 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.). In fall 2020, TAST was deployed to deter harbor seals that reliably aggregate in the mouth of Whatcom Creek in Bellingham, WA, from preying on fall runs of hatchery chum (O. keta) and Chinook (O. tshawytscha) salmon. Field observations were conducted between 2019-2021 to assess the shortterm (2020 fall salmon run only) and long-term (2019-2021 salmon runs) effectiveness of TAST on mitigating harbor seal predation. Analyses showed that TAST significantly decreased the duration that individuals remained at the creek but had variable effects on the foraging success of individuals in 2020. Generalized Linear Models showed no lingering effect of TAST on the presence or foraging success of seals the following year. I conclude that TAST may be an effective management tool in the short-term, but individual variability must be accounted for when managing predation by pinnipeds on depleted fishery species.