Abundance trends of two neon flying squid (Ommastrephes bartramii) stocks in the North Pacific

Abstract

Abstract Chen, C-S. 2010. Abundance trends of two neon flying squid (Ommastrephes bartramii) stocks in the North Pacific. – ICES Journal of Marine Science, 67: 1336–1345. Two stocks of neon flying squid (Ommastrephes bartramii) have been identified in the North Pacific, with differing life-history traits and geographic distributions, one in the Northeast Pacific and the other in the Northwest Pacific, each with seasonal cohorts. Both stocks are targeted by commercial fishing fleets from China, Japan, and Taiwan. The variability in abundance for each stock has been studied independently, but a comparable analysis between the two stocks is lacking. The abundance trends for the two stocks were examined using catch data from the Taiwanese squid fishery between 1986 and 2006. A time-series of monthly catch per unit effort and three explanatory variables, sea surface temperature in the presumed hatching grounds, the Southern Oscillation Index, and the number of vessels, were analysed using dynamic factor analysis to quantify squid abundance. The optimal model contained one common trend and all three explanatory variables. The Northwest Pacific and Northeast Pacific stocks exhibited opposing trends in abundance, and the results suggest that large-scale environmental factors, rather than regional factors, are more critical in influencing the abundance of oceanic squid species.