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The occurrence and density of Pacific saury Cololabis saira larvae and juveniles were examined in relation to environmental factors during the winter spawning season in the Kuroshio Current system, based on samples from extensive surveys off the Pacific coast of Japan in 2003–2012. Dense distributions of larvae and juveniles were observed in areas around and on the offshore side of the Kuroshio axis except during a large Kuroshio meander year (2005). The relationships of larval and juvenile occurrence and density given the occurrence to sea surface temperature (SST), salinity (SSS), and chlorophyll‐a concentration (CHL) were examined by generalized additive models for 10‐mm size classes up to 40 mm. In general, the optimal SST for larval and juvenile occurrence and density given the occurrence was consistently observed at 19–20°C. The patterns were more complex for SSS, but a peak in occurrence was observed at 34.75–34.80. In contrast, there were negative relationships of occurrence and density given the occurrence to CHL. These patterns tended to be consistent among different size classes, although the patterns differed for the smallest size class depending on environmental factors. Synthetically, the window for spawning and larval and juvenile occurrence and density seems to be largely determined by physical factors, in particular temperature. The environmental conditions which larvae and juveniles encounter would be maintained while they are transported. The survival success under the physically favorable but food‐poor conditions of the Kuroshio Current system could be key to their recruitment success.

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Tian, Y., Nashida, K., and Sakaji, H. 2013. Synchrony in the abundance trend of spear squid Loligo bleekeri in the Japan Sea and the Pacific Ocean with special reference to the latitudinal differences in response to the climate regime shift. – ICES Journal of Marine Science, 70: 968–979. Spear squid Loligo bleekeri is widely distributed in the Japanese coastal waters. The fisheries depend largely on four stocks: the southern and northern stocks both in the Japan Sea and the coastal regions of the Pacific. The catch per unit effort (cpue) for the northern stock in the Japan Sea decreased substantially during the 1980s but increased during the 1990s, while the abundance index for the southern stock showed the opposite trend. The cpue for the southern and northern stocks in the Pacific coast showed a similar pattern to that in the Japan Sea. The synchrony in the abundance trends between the Japan Sea and the Pacific Ocean, and latitudinal differences between the northern and southern stocks indicate the impact of the climate regime shift. Generalized additive model analysis identified significant effects of environmental factors. Increased water temperature had a positive effect on the northern stock but a negative effect on the southern stock in the Japan Sea and the Pacific, whereas El Niño–southern oscillation events and the Asian monsoon had additional significant effects on the Pacific stocks. These results suggest that the abundance trends of spear squid were largely forced by environmental factors with latitudinal differences in the response to the climate regime shift.