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SC/69B/SM/10
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Resource ID
22170
Access
Open
Document Number
SC/69B/SM/10
Full Title
The ongoing issue of fishery interactions among endangered Hawaiian false killer whales: repeated mouthline and dorsal fin injuries, stock and sex-specific trends, and early-life interactions
Author
A.E. Harnish, R.W. Baird, S.D. Mahaffy , A.B. Douglas, M.A. Kratofil, J.F. Shaff, T. Cullins, S.H. Stack, J. J. Currie, A.L. Bradford
Authors Summary
Harnish et al. analyzed mouthline and dorsal fin injuries that were consistent with hook-and-line fishing gear interactions for three populations of false killer whales in Hawaiian waters. Nearshore around the main Hawaiian Islands there are several thousand small-scale commercial and recreational hook-and-line fishermen with no observer coverage in any fishery, while offshore the U.S. deep-set longline fleet has had approx.20% observer coverage. The Hawai?i pelagic stock of false killer whales overlaps with both nearshore and offshore fisheries (including high seas foreign fisheries), the endangered main Hawaiian Islands (MHI) stock primarily overlaps with unobserved nearshore fisheries, and the Northwestern Hawaiian Islands stock has limited overlap with any fisheries. For individuals with both dorsal fin and mouthline photos available, the MHI stock had the highest rates of fisheries-related injuries (28.7% of individuals), followed by the pelagic stock (11.7%), while there were no fisheries-related injuries for individuals from the Northwestern Hawaiian Islands stock that had both photo types. Mouthline and dorsal fin injury rates were known to be negatively biased, as the median percentage of mouthline visible ranged from 50-60%, and individuals with excellent quality dorsal fin photos had a higher proportion of fisheries-related injuries. Females were significantly more likely to have fisheries-related injuries to the dorsal fin than males, although rates of mouthline injuries were similar. Some individuals from the MHI stock were documented with multiple fisheries-related injuries acquired on different occasions, indicating repeated interactions with fisheries.
Publisher
IWC
Publication Year
2024
Abstract
Monitoring bycatch in fisheries is essential for effective conservation and fisheries sustainability. False killer whales (Pseudorca crassidens) in Hawaiian waters are known to interact with both commercial and recreational fisheries, but limited observer coverage obscures the ability to document interactions and assess bycatch rates. Here, we assess fisheries interactions using photographic evidence of dorsal fin and mouthline injuries for three false killer whale stocks that vary in their spatial overlap with fisheries. Photographs from 504 individuals documented from 1999?2021 were scored for injuries to determine their consistency with fishery interactions