Standardizing catch per unit effort for the autumn and winter-spring cohorts of neon flying squid based on Japanese driftnet surveys
We present the catch per unit effort (CPUE) of the autumn and winter-spring cohorts of neon flying squid (Ommastrephes bartramii) based on Japanese driftnet surveys conducted during the summer in the western North Pacific. The size of squid caught with driftnets showed a bimodal distribution, and we assumed that individuals smaller than the boundary separating the two peaks represented the winter-spring cohort, while larger individuals represented the autumn cohort. The autumn cohort was mainly caught at stations east of 170oE, while the winter-spring cohort had a wider distribution. Standardized CPUE estimated with generalized additive models with temporal, spatial, and environmental variables showed large interannual variation for both cohorts. However, there were no clear increasing or decreasing trends over the years for either cohort.