Catch trend of bigeye tuna Thunnus obesus by purse seine using fish aggregating devices, by flag states and area of operation in tropical regions of the Western and Central Pacific Ocean

摘要

Seventeen members and cooperating non-members (CCMs) of the Western and Central Pacific Fisheries Commission (WCPFC) were responsible for 86% of the total catch of bigeye tuna Thunnus obesus by purse seine fishing from 2012 to 2014. We categorize the CCMs into an eastern, western and “other” group based on their main fishing areas. We found significant differences in the bigeye tuna catch per fish aggregating device (FAD) between the eastern group and the western group. We also estimated that the eastern group achieved a higher catch of bigeye tuna because of their increased fishing effort using FAD in the eastern area where there is a higher catch per unit effort for FAD. The regression analysis found significant correlations between the annual catch of bigeye tuna and the number of FAD sets. The average catch of bigeye tuna per single FAD set, estimated from the slope of the regression line, was 7.1 t in the eastern area and 2.7 t in the western area. An impact and risk plot composed of the slope of the regression line and the catch of bigeye tuna by each individual CCM was developed to improve management measures. Appropriate measures for the sustainable use of tuna resources in the region are discussed.