DISCUSSION
Most studies of squid distribution or migration have
used only in situ data collected by shipboard observations
or tagging experiments (e.g. Murata 1989). This
paper used DMSP/OLS nighttime visible images to
locate fishing vessel lights and determine the location
of fishing vessels in different areas and periods. Our
classification divided the Sea of Japan into 7 distinct
areas of seasonal fishing that correspond to the seasons
and locations of Todarodes pacificus fishing areas,
as reported by Araya (1976), Hatanaka et al. (1985),
and Murata (1989). Although information on fishing in
Korean waters is limited, our results also agree with
the annual variations in T. pacificus fishing area
reported by Choi et al. (1997).
When considering variations in squid abundance
and migration patterns, it is important to examine the
spatial and temporal patterns of squid fishing area formation
in the Sea of Japan. Our results show that seasonal
patterns may be related to physical processes
and to the annual life cycle of the squid. One of the
important findings of this study is that the 7 classified
areas coincide with the previously-reported oceanographic
characteristics of the Sea of Japan (see Table 3
for summary).
Oceanographic associations such as fronts or sea surface
temperature have been shown to influence Illex
argentinus in the South Atlantic (Waluda et al. 1999,
2001a,b). Fiedler & Bernard (1987) documented feeding
aggregations associated with oceanic fronts
detected by satellite imagery. Podestá et al. (1993)