1Hokkaido National Fisheries Research Institute, Kushiro, Hokkaido 085-0802, 2Fisheries Research Agency, Yokohama, Kanagawa 236-8648, Japan
The distribution pattern of juvenile Japanese common squid, Todarodes pacificus, in the Kuroshio-Oyashio transition region was investigated in 1994-1996. The investigation was carried out in the offshore area of Boso-Joban districts every April. The juvenile squids of 5-35mm (in dorsal mantle length, mainly 7-15mm) were caught with 2m ring-plankton-net (mesh size 3mm). The research area was divided into four sub-areas by the hydrographical conditions namely, Oyashio area, Cold water area, Warm water area, and Kuroshio area. The distribution patterns of juvenile squids were compared among these four water areas. Juveniles occurred dominantly in the Warm water area. In the other areas, juvenile density was relatively low. High density occurrences of juveniles were recognized around the frontal area. Differences in the distribution pattern among size classes were not recognized. The distribution pattern of juvenile squids might be due to passive transport by the ocean current. The warm water area where many juvenile were distributed is a warm water area of more than 10°C at 100m depth and corresponds to the area with high biomass of zooplankton. The passive system of transfering juveniles into this area influences the survival and growth for later juvenile stages.