1Marine Fisheries Research and Development Center (JAMARC), Fisheries Research Agency, Yokohama, Kanagawa 220-6115, 2Faculty of Marine Science, Tokyo University of Marine Science and Technology, Minato, Tokyo 108-8477, Japan
Two different-shaped hooks, ‘Tainawa-bari’ and ‘Mutsu-bari’, are currently used by commercial longline fisheries targeting red tilefish in the East China Sea. The shape of ‘Mutsu-bari’ is more circular than ‘Tainawa-bari’. For protecting young small fish, selecting an appropriate hook size is a potential resource conservation measure. Hence, the size selectivity of each hook should be evaluated. Comparative fishing experiments were conducted using both ‘Tainawa-bari’ of four sizes (Japanese nominal number #10, 12, 14, and 16) and ‘Mutsu-bari’ of #13.5 size in the East China Sea. The parameters of size selectivity of ‘Tainawa-bari’ and ‘Mutsu-bari’ were estimated by the SELECT method under the assumption of geographical similarity on upper jaw length and hook width of a given retention probability. As a result of AIC model selection, a single master curve using a short hook width for ‘Mutsu-bari’ as the hook width parameter was chosen for expressing hook size selectivity of the two hooks, which implied no difference in size selectivity between the two different-shaped hooks. Thus, the single master curve for hook size selectivity and relative fishing intensity of each hook can be used for fisheries resource management.