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Testing a passive deterrent on longlines to reduce sperm whale depredation in the Gulf of Alaska

TitleTesting a passive deterrent on longlines to reduce sperm whale depredation in the Gulf of Alaska
Publication TypeJournal Article
Year of Publication2015
AuthorsO'Connell V., Straley J., Liddle J., Wild L., Behnken L., Falvey D., Thode A
JournalIces Journal of Marine Science
Date Published2015/05
Type of ArticleArticle
ISBN Number1054-3139
Accession NumberWOS:000356233800037
Keywordsatlantic; commercial fishing; depredation; fishery; Gulf of Alaska; longline; mammals; marine; passive deterrent; physeter-macrocephalus; sablefish; sperm whales

In Alaska, sperm whale (Physeter macrocephalus) depredation on longline sets has increased since implementation of the Individual Fishing Quota programme in 1995. A collaborative effort (SEASWAP) between longliners, scientists, and managers has undertaken research to evaluate this depredation with a primary objective to develop and test a passive deterrent that would reduce depredation without reducing catch rate of sablefish (Anoplopoma fimbria). Commercial longliners, fishing for their own sablefish quotas during the regular season, deployed beaded gear (25 mm lucite beads attached to gangions) with control gear and set recorders to collect acoustic data. Beaded and control gear were randomly assigned by skate quad (672 hooks) with 5 quads in each longline set. Acoustic recorders were used to document sperm whale creak-pause events, representative of depredation of the longline gear. Although there were more sablefish per skate quad on the beaded gear and there was a decrease in depredation events on the beaded gear compared with the control, neither effect was significant (p = 0.205 and 0.364, respectively). The SEASWAP project is testing other deterrent strategies including gear modifications and the establishment of a sighting network to improve avoidance.

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