Basis of acoustic discrimination of Chinook salmon from other salmons by echolocating Orcinus orca.
The "resident" ecotype of killer whales (Orcinus orca) in the waters of British Columbia and Washington State have a strong preference for Chinook salmon even in months when Chinook comprise less than about 10% of the salmon population. The foraging behavior of killer whales suggests that they depend on echolocation to detect and recognize their prey. In order to determine possible cues in echoes from salmon species, a series of backscatter measurements were made at the Applied Physics Laboratory (Univ. of Wash.) Facility on Lake Union, on three different salmon species using simulated killer whale echolocation signals. The fish were attached to a monofilament net panel and rotated while echoes were collected, digitized and stored on a laptop computer. Three transducer depths were used; same depth, 22° and 45° above the horizontal plane of the fish. Echoes were collected from five Chinook, three coho and one sockeye salmon. Radiograph images of all specimens were obtained to examine the swimbladder shape and orientation. The results show that echo structure from similar length but different species of salmon were different and probably recognizable by foraging killer whales.
Marine Mammal Research Program, Hawaii Institute of Marine Biology, University of Hawaii, P.O. Box 1106, Kailua, Hawaii 96734, USA.
Whitlow W L
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John K
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Horne
Christopher
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Jones
D000162:Acoustics / Q000295:instrumentation; D000400:Air Sacs / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D000818:Animals; D003463:Cues; D004192:Discrimination, Psychological; D004455:Echolocation; D017684:Oncorhynchus kisutch / Q000033:anatomy & histology; D011235:Predatory Behavior; D011859:Radiography; D021641:Recognition, Psychology; D012474:Salmon / Q000033:anatomy & histology*; D012542:Scattering, Radiation; D013018:Sound Spectrography; D013997:Time Factors; D014159:Transducers; D014828:Vocalization, Animal; D050685:Whale, Killer / Q000502:physiology*