Can Circle Hooks Improve Western Atlantic Sailfish, Istiophorus Platypterus, Populations?
Abstract:Although many uncertainties surround the status of western atlantic sailfish, Istiophorus platypterus (shaw, 1792), stock size (b) is considered below and fishing mortality rate (F) above the targets that would allow maximum sustainable yield (MSY). One means of improving status is to implement live-release policies and to employ circle hooks to increase release survival. In the present study, we examined the efficacy of a switch to circle hooks to achieve population-level BMSY and FMSY targets. First, we evaluated the scope that exists to employ circle hooks and adopt live-release policies. Second, we decremented recent landings by the reductions that could be achieved through live release and increase in survival between circle hooks and traditional J-hooks. Third, we projected these landings in the bayesian surplus production model. Assuming that landings in the non-release fleets remain constant, the current percentages of circle hooks (approximately 25%) and live release (approximately 25%) could reduce landings by 7%–8%. This measure alone would have less than a one percentage point increase in probability of improving status. With maximum practicable live release of around 50%, because many fleets market sailfish, and 100% circle hook use, landings could be reduced by 13%–23%. This would only have a 0.42–1.36 and 0.45–2.56 percentage point increase in the probability of meeting biomass and fishing mortality targets, respectively. While circle hooks can be a useful tool to convert landed fish to live releases, they are unlikely to meet current targets for western atlantic sailfish unless combined with other management that would reduce overall landings.
Document Type: Research Article
Publication date: July 1, 2012
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