The potential use of time-area closures to reduce catches of bigeye tuna in the purse-seine fishery of the eastern Pacific Ocean
Skipjack (Katsuwonus pelamis), yellowfin (Thunnus alba-cares), and bigeye (Thunnus obesus) tunas are caught by purse-seine vessels in the eastern Pacific Ocean (EPO). Although there is no evidence to indicate that current levels of fish ing-induced mortality will affect the sustainability of skipjac...
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Veröffentlicht in: | Fishery bulletin (Washington, D.C.) D.C.), 2007-01, Vol.105 (1), p.49-61 |
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Format: | Artikel |
Sprache: | eng |
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Zusammenfassung: | Skipjack (Katsuwonus pelamis), yellowfin (Thunnus alba-cares), and bigeye (Thunnus obesus) tunas are caught by purse-seine vessels in the eastern Pacific Ocean (EPO). Although there is no evidence to indicate that current levels of fish ing-induced mortality will affect the sustainability of skipjack or yellowfin tunas, fishing mortality on juvenile (younger than 5 years of age) bigeye tuna has increased, and overall fish ing mortality is greater than that necessary to produce the maximum sustainable yield of this species. We investigated whether time-area clo sures have the potential to reduce purse-seine bigeye catches with out significantly reducing skipjack catches. Using catch and effort data for 1995-2002, we identified regions where the ratio of bigeye to skipjack tuna catches was high and applied simple closed-area models to investi gate the possible benefits of time-area closures. We estimated that the most optimistic and operationally feasible 3-month closures, covering the equa torial region of the EPO during the third quarter of the year, could reduce bigeye catches by 11.5%, while reduc ing skipjack tuna catches by 4.3%. Because this level of bigeye tuna catch reduction is insufficient to address sustainability concerns, and larger and longer closures would reduce catches of this species signficantly, we recommend that future research be directed toward gear technology solutions because these have been successful in many other fisheries. In particular, because over 50% of purse-seine catches of bigeye tuna are taken in sets in which bigeye tuna are the dominant species, methods to allow the determination of the species composition of aggregations around floating objects may be important. |
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ISSN: | 0090-0656 |