Biological aspects of the butterfly kingfish Gasterochisma melampus : distribution, total catch, size composition and CPUE

Biological aspects of butterfly kingfish Gasterochisma melampus were examined using Japanese longline fishery data and research data collected for over 20 years. Butterfly kingfish were distributed in a continuous band around the circumpolar region between 35°S and 45°S. The southern limit of distribution corresponded with the sub-Antarctic front. The estimated global total annual catch for butterfly kingfish ranged from 613 to 3699 t (mean 1859 t) with Japan taking the largest proportion of the total catch. Large, adult butterfly kingfish spawn in the south-eastern Pacific, whereas smaller, immature fish are distributed in feeding grounds in the area extending across the Atlantic and Indian Oceans to the south-western Pacific Ocean. Catch per unit effort (CPUE) data for fish in the feeding grounds from 1993 to 2016 were compared with the CPUE value from 1970. These data indicate that the stock is currently not likely to be depleted.