Northwest Fisheries Science Center

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Document Type: Journal Article
Center: NWFSC
Document ID: 4792
Title: Auditory detection of ultrasonic coded transmitters by seals and sea lions
Author: Kane A. Cunningham, Sean A. Hayes, A. Michelle Wargo Rub, Colleen Reichmuth
Publication Year: 2014
Journal: Journal of the Acoustical Society of America
Volume: 135
Issue: 4
Pages: 1978-1985
Keywords: coded transmitters,pinniped hearing,

 Ultrasonic coded transmitters (UCTs) are high-frequency acoustic tags that are often used to conduct survivorship studies of vulnerable fish species. Recent observations of differential mortalilty in tag control studies suggest that fish instrumented with UCTs may be selectively targeted by marine mammal predators, thereby skewing valuable survivorship data. In order to better understand the ability of pinnipeds to detect UCT outputs, we obtained behavioral high-frequency hearing thresholds from a trained harbor seal (Phoca vitulina) and a trained California sea lion (Zalophus californianus). Thresholds were measured for extended (500 ms) and brief (10 ms) 69 kHz narrowband stimuli, as well as for a stimulus recorded directly from a Vemco V16-3H UCT, which consisted of eight 10 ms, 69 kHz pure-tone pulses. Detection thresholds for the harbor seal were as expected based on existing audiometric data for this species, while the California sea lion was 33 dB more sensitive than previously predicted at 69 kHz.  Given measured thresholds of 113 dB re 1mPa and 124 dB re 1mPa respectively, both species are likely able to detect the Vemco V16-3H underwater from distances exceeding 500 m in typical natural conditions, suggesting that these species are capable of using UCTs to detect free-ranging fish.

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Theme: Recovery, Rebuilding and Sustainability of Marine and Anadromous Species
Foci: Describe the relationship among human activities and species stock status, recovery, rebuilding and sustainability.