Influence of El Nino/La Nina on the western winter-spring cohort of neon flying squid (Ommastrephes bartramii) in the northwestern Pacific Ocean

Ommastrephes bartramii is an oceanic squid distributed widely in the North Pacific, and its western winter-spring cohort is the target of a traditional squid fishery. Commercial fisheries data from the Chinese mainland squid-jigging fleet for the period 1995-2004 were analysed with respect to environmental variables. Sea surface temperature anomalies (SSTA) in the Nino 3.4 region had the strongest negative correlation with the SSTA of feeding and spawning grounds of the squid, with a time-lag of three and eight months (p < 0.05), respectively. A La Nina event would result in a decrease in squid recruitment through variability in environmental conditions on the spawning grounds, whereas an El Nino event would lead to environmental conditions favourable to squid recruitment. El Nino/La Nina events also influenced squid distribution on the feeding grounds, resulting in a northward shift of the fishing grounds in La Nina years and a southward shift in El Nino years. A multiple linear regression equation was derived to describe the dependence of the squid abundance index on environmental variables.