Distribution and migration of the common squidTodarodes pacificus in the Yellow Sea

Study of the distribution and migration of the common squid,Todarodes pacificus Steenstrup, based on the index of important fishing ground (P _i) and fisheries statistics on the Yellow Sea and northern East China Sea during 1980–1991 showed that:

1. Its catch in the fishing period (June to November) is 91.77% of the annual yield. The fishing ground distributes over the northern and middle Yellow Sea and adjacent area of the Changjiang Estuary.
2. It over-winters in the northern East China Sea and waters adjacent to Goto Island from December to February and spawns in waters near Haijiao Island and west of Kyushu. The main stock migrates along 123 °30′E to the Changjiang Estuary, Haizhou Bay, offsea from Shidao to Qingdao, mideastern Yellow Sea, and offsea Weihai and Haiyang Island succesively for feeding after April. The surplus stock migrates again to the wintering ground in December.
3. The favorable feeding temperature is 6–23°C (optimum of 13–20°C in the changjiang Estuary and 7–13°C in the northern and middle Yellow Sea). Its distributing area relates to the area of the Kuroshio influence.
4. It habitually migrates vertically, living at the surface at night and at the bottom in daytime. But this tendency changes somewhat in different stages.