Todarodes pacificus migrates seasonally from the
southern Sea of Japan and is distributed from the East
China Sea to the Maritime Province of Siberia and Sea
of Okhotsk (Fig. 2). Over the last century, studies of
squid in Japanese waters have focused on biology and
fisheries. Numerous studies have examined spawning
areas, migration routes and spawning seasons. T. pacificus
spawns in 3 seasons: autumn (September–November),
winter (December–February), and spring/
summer (all other months) (Murata 1989). Although
recruitment occurs throughout the year, 2 spawning
groups maintain the stocks in the Sea of Japan. The
main spawning areas for both autumn and winter
spawning groups are thought to be around the
Tsushima Strait (Fig. 2). Araya (1976) the described
migration and fishing areas of T. pacificus in the northern
waters of Japan, and Hatanaka et al. (1985) and
Murata (1989, 1990) further detailed the migration of
T. pacificus also in northern waters of Japan. Kiyofuji
et al. (1998) analyzed sea surface temperature (SST)
imagery to identify the spawning areas of T. pacificus.
The schematic map in Fig. 2 (modified from Murata
1989, 1990), combines spawning and migration data
from the above studies