Examining Management Issues for Incidentally Caught Species in Highly Migratory Species Fisheries in the Western and Central Pacific Ocean

Last modified: 
December 14, 2019 - 9:36am
Type: Thesis
Year of publication: 2014
Authors: Valerie Chan
Institution: University of California
City: Los Angeles
Academic department: Environmental Science & Engineering

In 2010, the Western and Central Pacific Fisheries Commission (WCPFC) adopted a conservation and management measure (CMM) for North Pacific striped marlin (Kajikia audax). A 2012 stock assessment indicated that the limits in this CMM were insufficient to prevent overfishing of this stock. I used a survey employing Analytical Hierarchy Process (AHP), demographic and short answer questions to collect information on stakeholder opinions on select criteria and management options if a new CMM were to be developed. Management options with the highest ratings were circle hooks and catch limits while the lowest ratings were for a retention ban. Respondents had varied opinions on the need to manage striped marlin and additional research could bolster support for further management. An Ecopath with Ecosim model was then used to evaluate how implementation of different management measures for North Pacific striped marlin would impact biomasses of striped marlin and other groups. Increases in fishing effort had the greatest impact on relative biomass, with declines in most of the higher level trophic groups and increases in many of the mid-level trophic groups. The use of circle hooks and the elimination of the shallowest hooks from deep longline sets led to increases in striped marlin biomass, and effects to other species were limited. Recovery of striped marlin was greatest if measures were implemented to all fleets; conservation measures adopted unilaterally by the United States would have a minimal impact on biomass recovery for this species. Lastly, I discussed the benefits and costs of broader retention policies for purse seine and longline tuna fisheries in the western and central Pacific Ocean (WCPO). Using bycatch data from observers and logbooks from the U.S. purse seine and longline fleets operating in the WCPO, this dissertation documents the types and magnitude of fish discarded. Expanding retention policies beyond the target tunas and to other gear types would further reduce discarding and possibly provide stronger incentives to develop and use more selective techniques. Beyond impacts to the ecosystem and fisher behavior, adopting broader retention policies may have other implications, and this dissertation explored those implications on vessels, processors, and communities.

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