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ESR 5:309-323 (2008)  -  DOI:

Reducing seabird bycatch in the Hawaii longline tuna fishery

Eric Gilman1,2,*, Donald Kobayashi3,4, Milani Chaloupka5

1IUCN Global Marine Programme, 2718 Napuaa Place, Honolulu, Hawaii 96822, USA
2Centre for Ecology and Conservation, University of Exeter, Cornwall Campus, Penryn TR10 9EZ, UK
3US NOAA Fisheries, Pacific Islands Fisheries Science Center, 2570 Dole Street, Honolulu, Hawaii 96822, USA
4Department of Environmental Sciences, University of Technology, Sydney, New South Wales 2007, Australia
5Ecological Modeling Services, PO Box 6150, University of Queensland, St. Lucia, Queensland 4067, Australia

ABSTRACT: Mortality in longline fisheries represents a global threat to some species of pelagic seabirds. Regulations were adopted in 2001 to reduce seabird bycatch in the Hawaii longline tuna fishery. We used a Poisson generalized additive regression modeling approach to evaluate the change in seabird bycatch rates from the pre- to post-regulation period, and to evaluate the efficacy of alternative combinations of seabird bycatch reduction methods employed during the post-regulation period. Informative covariates of temporal and geo-referenced spatial effects of fishing effort and sampling variation commonly found with count data were included in the model to provide a better inference of the effect of employing required changes in fishing gear and methods. We found a significant 67% (95% CI: 62 to 72) reduction in the seabird bycatch rate following the introduction of regulations. Post-regulation, sets employing 4 different combinations of seabird avoidance methods all resulted in significant reductions to the pre-regulation seabird catch rate. Employing side-setting and 60 g weights was the only combination with no seabird captures during the post-regulation period. Using heavier branch line weights and treated bait (thawed and dyed blue) both significantly reduced seabird catch rates. Temporal and spatial distribution of fishing effort and the timing of initiating setting were also significant factors affecting seabird bycatch rates: time-area closures and restricting the timing of setting could further reduce seabird bycatch. A substantial proportion of seabird captures occurred south of the area where mitigation measures are required: moving the southern boundary farther south would further reduce seabird catches.

KEY WORDS: Albatross · Bycatch · Fisheries · Longline · Mitigation · Seabird

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Cite this article as: Gilman E, Kobayashi D, Chaloupka M (2008) Reducing seabird bycatch in the Hawaii longline tuna fishery. Endang Species Res 5:309-323.

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