Size composition of neon flying squid caught by Japanese squid jigging vessels in waters east of 170°E in 2025 and a preliminary estimation of catch by cohort

This study investigates the relationship between size-box categories and mantle length of the neon flying squid (Ommastrephes bartramii, NFS) caught by Japanese squid jigging vessels in the North Pacific Ocean. On-board size measurements of mantle lengths of squid caught by commercial jigging were conducted from May to September in 2025, covering five size-box categories. In total, the mantle lengths of 3023 individuals were measured. Based on these measurement results and measurement data from previous studies in 2012–2013, the proportions of the winter-spring cohort were calculated for each size-box category. By applying these proportions to the catch by size-box categories, the catch proportion of the winter-spring cohort in the total catch was preliminarily estimated to be an average of 4.1% for the period from May to September 2010–2025.