Gulf of Alaska | Mammals MASTER’S ORAL PRESENTATION Assessing the effects of Targeted Acoustic Startle Technology on the foraging success of individual harbor seals Presenter: Kathleen Mckeegan , k.a.mckeegan@gmail.com, Western Washington University Kate Clayton , claytok2@wwu.edu, Western Washington University Alejandro Acevedo-Gutiérrez , aceveda@wwu.edu, Western Washington University
Matthew Zinkgraf , zinkgrm@wwu.edu, Western Washington University Andrea Mendez-Bye , andrea.mendez.bye1@gmail.com, Oceans Initiative Stephanie Reiss , stephanie@oceansinitiative.org, Oceans Initiative Rob Williams , rob@oceansinitiative.org, Oceans Initiative Erin Ashe , erin@oceansinitiative.org, Oceans Initiative Thomas Goetz , tg45@st-andrews.ac.uk, University of St. Andrews Vincent Janik , vj@st-andrews.ac.uk, University of St. Andrews
Rebounding pinniped populations have led to conflicts with fisheries over commercially important prey species and subsequent calls for the management of pinniped predation. In the Salish Sea, harbor seal ( Phoca vitulina ) populations are suspected of impeding the recovery of Pacific salmon ( Oncorhynchus spp. ) stocks. Acoustic deterrent devices (ADDs) are designed to aid the recovery of depleted stocks by deterring pinnipeds from foraging in areas of high prey abundance. Most ADDs use painful sound signals, which can lead to hearing loss, habituation, or injury to non-target species. A new ADD called Targeted Acoustic Startle Technology (TAST) appears to decrease seal presence and predation with no evidence of harm or habituation. However, the effects of TAST on the foraging success of individual pinnipeds in the short and long-term are unknown. We compared the presence and capture efficiency (number of salmon consumed per seal per visit) of individual harbor seals across TAST-on conditions and control conditions. 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 short-term (2020) and long- term (2019-2021) effectiveness of TAST on mitigating harbor seal predation and presence. Based on photo-identification, individual harbor seals were associated with foraging successes across all three years of the study. During TAST deployment in 2020, 85% of individual seals that were exposed to TAST returned to forage in the creek on a subsequent observation. Generalized linear mixed-effect models showed that TAST reduced the duration (min) harbor seals remained at the creek by an estimated 49% and reduced the overall foraging success by an estimated 34.5%. However, the effect of TAST across individuals varied greatly, with some strongly affected and others unaffected. Generalized linear models showed no lingering effect of TAST on individual foraging success the year after deployment. Our analyses suggest TAST may be an effective tool to manage pinniped predation but is not equally effective across all predators in the population. Individual variability in foraging success must be accounted for when managing predation by pinnipeds on depleted fishery species.
Alaska Marine Science Symposium 2023 27
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