Isoda & Saitoh (1993) analyzed satellite SST images
and hydrographic data along the east coast of Korea.
Their research showed warm eddies intruding northward
from spring to summer around the Ulleung Basin,
and the presence of relatively stable northward currents
along the eastern coast of Korea in autumn. Kim
et al. (2002) reported the characteristics of the temporal
variations in sea level at Ulleung Island and concluded
that short-term variations in sea level are
caused primarily by the movement of the warm eddies
around the Island. Choi et al. (1997) noted that the
squid-angling fishery started to move north in April
and then south in September. Mesoscale eddies are
also important in the enhancement of phytoplankton
production (e.g. Saitoh et al. 1998) and the distribution
of Pacific sardine larvae (Logerwell & Smith 2001). In
our results, Class 2 fishing areas were mainly distributed
around Ulleung Island from June to December. If
higher prey densities are associated with shelf-break
fronts and eddies, the consistent presence of fronts and
eddies comprises predictable feeding locations for
higher trophic level feeders which take advantage of
increased prey densities, and also a predictable fishing
area. The dynamics of warm-water eddies probably
also affect squid fishing area formations, as suggested
by the fishing area distributions of Class 2 and the
study of Choi et al. (1997).
In the laboratory, Bower & Sakurai (1996) observed
that Todarodes pacificus females rest on the bottom
just before spawning. Similarly, bottom trawls often
collect exhausted, spent females on the shelf and slope
at 100 to 500 m depth (Hamabe & Shimizu 1966), indicating
that spawning females would concentrate at
depths between 100 and 500 m. Thus, topography may
affect squid distribution. The main autumn and winter
spawning grounds form around the Tsushima Strait
(Murata 1989, and present Fig. 2). Kiyofuji et al. (1998)
identified the inshore area of Korea’s east coast as a
possible spawning ground, primarily using satellite
SST and topography data. Class 5 corresponds to this