Fishery characteristics of large bigeye tuna Thunnus obesus caught by longline fishing ‘Kajiki-nawa’ along the Boso coast, Japan

Abstract

The catch characteristics of large bigeye tuna fish caught by near-shore longline boats, NL, ‘Kajiki-nawa’ along the Boso coast were analyzed. NL were operated around the Kuroshio channel of the Boso coast from November to June of previous year. The fishing line operated a shallow line with a reach of about 70 m deep during the daytime, and mainly caught fish with a fork length of 110 cm or more. Monthly mean surface water temperature for the bigeye tuna was 18.5–23.2°C, which is different from records for bigeye tuna so far, with fish caught in the high-water temperature area at shallow water depth during the day.