Impact of paralarvae and juveniles feeding environment on the neon flying squid (Ommastrephes bartramii) winter–spring cohort stock

In this study, we found that there were significant positive correlations between the catch per unit effort (CPUE, a squid abundance index) for the neon flying squid (Ommastrephes bartramii) winter–spring cohort and the satellite‐derived chlorophyll a concentrations in their spawning grounds located at 140–160°E where 21°C < sea surface temperature < 25°C from February to May. The spawning grounds of the winter–spring cohort are located in a quiet stream region, and a particle tracking experiment, based on the velocity field obtained from an ocean data assimilation system, showed that paralarvae and juveniles aged <90 days remained in their spawning grounds and the chlorophyll a concentration in their habitat had a significant positive correlation with the CPUE. A backward particle tracking experiment also showed that the chlorophyll a concentration in the spawning grounds had a significant positive correlation with the autumn–winter mixed layer depth. Based on these results, we hypothesize that the CPUE interannual variability is caused by variations in the feeding environment of the paralarvae and juveniles, which may be linked to autumn–winter mixed layer depth variations.