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Reducing sea turtle interactions in the Hawaii-based longline swordfish fishery

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Gilman, E and Kobayashi, DR and Swenarton, T and Brothers, N and Dalzell, P and Kinan-Kelly, I (2007) Reducing sea turtle interactions in the Hawaii-based longline swordfish fishery. Biological Conservation, 139 (1- 2). pp. 19-28. ISSN 0006-3207

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Abstract

The reduction of sea turtle mortality in fisheries may contribute to recovering populations.
To reduce turtle interactions, regulations for the Hawaii-based longline swordfish fishery
required vessels to switch from using a J-shaped hook with squid bait to a wider circleshaped
hook with fish bait. Analyses of observer data showed that, following the introduction
of the regulations, significant and large reductions in sea turtle and shark capture rates
occurred without compromising target species catches. Capture rates of leatherback and
loggerhead turtles significantly declined by 83% and 90%, respectively. The swordfish catch
rate significantly increased by 16%. However, combined tuna species and combined mahimahi,
opah, and wahoo catch rates significantly declined by 50% and 34%, respectively. The
shark catch rate significantly declined by 36%, highlighting the potential for the use of fish
instead of squid for bait to contribute to addressing concerns over the sustainability of current
levels of shark exploitation. There was also a highly significant reduction in the proportion
of turtles that swallowed hooks (versus being hooked in the mouth or body or
entangled) and a highly significant increase in the proportion of caught turtles that were
released after removal of all terminal tackle, which may increase the likelihood of turtles
surviving the interaction. A quarter of turtle captures were in clusters (>1 turtle caught
per set and consecutive sets with turtle captures), which is substantially higher than predicted
by chance if the events were independent. This suggests that turtles aggregate at foraging
grounds and that instituting methods to avoid real-time turtle bycatch hotspots may
further reduce turtle interactions. There was no significant correlation between turtle and
swordfish catch rates (vessels with high swordfish CPUE do not necessarily have high turtle
CPUE), indicating that there may be a fishing practice or gear design causing some vessels
to have low turtle catch rates without compromising swordfish catch rates.

Item Type: Article
Journal or Publication Title: Biological Conservation
Publisher: Elsevier BV
Page Range: pp. 19-28
ISSN: 0006-3207
Identification Number - DOI: 10.1016/j.biocon.2007.06.002
Additional Information:

The definitive version is available at http://www.sciencedirect.com

Date Deposited: 07 Apr 2008 14:39
Last Modified: 18 Nov 2014 03:35
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