False killer whales and fisheries interactions in Hawaiian waters: Evidence for sex bias and variation among populations and social groups |
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Authors: | Robin W. Baird Sabre D. Mahaffy Antoinette M. Gorgone Tori Cullins Dan J. McSweeney Erin M. Oleson Amanda L. Bradford Jay Barlow Daniel L. Webster |
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Affiliation: | 1. Cascadia Research Collective, Olympia, Washington 98501, U.S.A;2. Wild Dolphin Foundation, Waianae, Hawai‘i 96792, U.S.A;3. Wild Whale Research Foundation, Box 139, Holualoa, Hawai‘i 96724, U.S.A;4. Pacific Islands Fisheries Science Center, NOAA Fisheries, Honolulu, Hawai‘i 96818, U.S.A;5. Southwest Fisheries Science Center, La Jolla, California 92037, U.S.A |
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Abstract: | We assessed scarring patterns as evidence of fisheries interactions for three populations of false killer whales in Hawai‘i. Bycatch of the pelagic population in the tuna longline fishery exceeds their Potential Biological Removal level. Scarring was assessed by seven evaluators as consistent, possibly consistent, or not consistent with fisheries interactions, and average scores computed. Scores were highest for scarred main Hawaiian Island (MHI) false killer whales, followed by pelagic and Northwestern Hawaiian Island (NWHI) individuals. Considering only whales for which the majority of evaluators scored scarring as consistent revealed significant differences among populations in the percentage of individuals scarred; MHI: 7.5%, pelagic: 0%, NWHI: 0%. Assessment by social cluster for the MHI population showed that 4.2% of Cluster 1, 7.1% of Cluster 2, and 12.8% of Cluster 3 individuals had such scarring, although differences between clusters were not statistically significant. There was a significant sex bias; all sexed individuals (n = 7) with injuries consistent with fisheries interactions were female. The higher proportion of MHI individuals with fisheries‐related scarring suggests that fisheries interactions are occurring at a higher rate in this population. The bias towards females suggests that fisheries‐related mortality has a disproportionate impact on population dynamics. |
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Keywords: | bycatch injuries fisheries interactions fisheries sex bias false killer whales Hawai‘ i |
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