title: Auditory detection of ultrasonic coded transmitters by seals and sea lions.
abstract: 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 mortality 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, behavioral high-frequency hearing thresholds were obtained 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 much more sensitive than predicted. Given measured detection thresholds of 113 dB re 1 μPa and 124 dB re 1 μPa, respectively, both species are likely able to detect acoustic outputs of the Vemco V16-3H under water from distances exceeding 200 m in typical natural conditions, suggesting that these species are capable of using UCTs to detect free-ranging fish.
authors.affiliation: Department of Ocean Sciences, Long Marine Laboratory, University of California, Santa Cruz, 100 Shaffer Road, Santa Cruz, California 95060.
authors.forename: Kane A
authors.initials: KA
authors.lastname: Cunningham
authors.affiliation: Fisheries Ecology Division, Southwest Fisheries Science Center, National Marine Fisheries Service, National Atmospheric and Oceanographic Administration, Santa Cruz, California 95060.
authors.forename: Sean A
authors.initials: SA
authors.lastname: Hayes
authors.affiliation: Fish Ecology Division, Northwest Fisheries Science Center, National Marine Fisheries Service, National Atmospheric and Oceanographic Administration, Seattle, Washington 98112.
authors.forename: A
authors.initials: A
authors.lastname: Michelle Wargo Rub
authors.affiliation: Institute of Marine Sciences, Long Marine Laboratory, University of California, Santa Cruz, Santa Cruz, California 95060.
authors.forename: Colleen
authors.initials: C
authors.lastname: Reichmuth
mesh_terms: D000161:Acoustic Stimulation; D000818:Animals; D001301:Audiometry, Pure-Tone; D001307:Auditory Perception; D001309:Auditory Threshold; D003463:Cues; D004784:Environmental Monitoring / Q000295:instrumentation*; D004867:Equipment Design; D005260:Female; D005399:Fishes / Q000502:physiology*; D008297:Male; D046049:Phoca / Q000502:physiology*; D011235:Predatory Behavior; D046070:Sea Lions / Q000502:physiology*; D017603:Signal Detection, Psychological; D013018:Sound Spectrography; D014159:Transducers; D014465:Ultrasonics / Q000295:instrumentation*