Cues, creaks, and decoys: using passive acoustic monitoring as a tool for studying sperm whale depredation

TitleCues, creaks, and decoys: using passive acoustic monitoring as a tool for studying sperm whale depredation
Publication TypeJournal Article
Year of Publication2015
AuthorsThode A, Mathias D., Straley J., O'Connell V., Behnken L., Falvey D., Wild L., Calambokidis J, Schorr G., Andrews R., Liddle J., Lestenkof P.
JournalIces Journal of Marine Science
Volume72
Pagination1621-1636
Date Published2015/05
Type of ArticleReview
ISBN Number1054-3139
Accession NumberWOS:000356233800034
Keywordsacoustic deterrent; Alaska; click; commercial fishing; depredation; diving behavior; gulf; Gulf of Alaska; harbor seals; longline; marine mammals; orcinus-orca; passive acoustic monitoring; physeter-macrocephalus; porpoises phocoena-phocoena; prey-capture; rates; sablefish; sperm; underwater sounds; whales
Abstract

Since 2003, a collaborative effort (SEASWAP) between fishers, scientists, and managers has researched how Alaskan sperm whales locate demersal longline fishing activity and then depredate sablefish from gear. Sperm whales constantly produce relatively low-frequency biosonar signals whenever foraging; therefore, over the past decade, passive acoustic monitoring (PAM) has become a basic tool, used for both measuring depredation activity and accelerating field tests of potential depredation countermeasures. This paper reviews and summarizes past published PAM research on SEASWAP, and then provides a detailed example of how PAM methods are currently being used to test countermeasures. The review covers two major research thrusts: (i) identifying acoustic outputs of fishing vessels that provide long-distance "cues" that attract whales to fishing activity; and (ii) validating whether distinctive "creak" sounds can be used to quantify and measure depredation rates, using both bioacoustic tags and statistical comparisons between visual and acoustic depredation estimates during federal sablefish surveys. The latter part of the paper then provides an example of how PAM is being used to study a particular potential countermeasure: an "acoustic decoy" which transmits fishing vessel acoustic cues to attract animals away from true fishing activity. The results of an initial 2011 field trial are presented to show how PAM was used to design the decoy signals and monitor the efficacy of the deployment. The ability of PAM to detect both whale presence and depredation behaviour has reduced the need to deploy researchers or other specialists on fishing cruises. Instead, volunteer fishers can deploy "user-friendly" acoustic recorders on their gear, greatly facilitating the testing of various deterrents, and providing the industry and regulators a convenient and unobtrusive tool for monitoring both the scale and long-term spread of this behaviour across the Alaskan fishery.

DOI10.1093/icesjms/fsv024
Student Publication: 
No
Research Topics: 
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