Spatial distribution of Todarodes pacificus
fishing area
The yellow areas in Fig. 8 were extracted by 2-level
slicing methods (see ‘Materials and methods’) and represent
fishing-vessel lights, particularly those fishing
for Todarodes pacificus. The fishing areas were mainly
around the Tsushima Strait in January, extending to
Ulleung Island along the east coast of Korea and the
Oki Islands near the Japanese coast. February and
March showed similar spatial patterns in fishing area.
Their extent, however, seemed smaller than in January.
In April, fishing areas spread into 2 branches at latitude
36°N, longitude 127°E, with 1 branch located
along the east coast of Korea and the other along
Japan’s Honshu Island. The patterns visible in April
intensified in May, especially in Korean waters. In
Japanese waters, the fishing areas in May extended
from the Oki Islands to Sado Island.
In June, a squid fishing area formed along the northern
edge of Yamato Rise, and the northern edge of the
squid fishing areas along the Japan coast had extended
to the western Tsugaru Strait and to waters off
southwestern Hokkaido. In July (Fig. 8), fishing areas
contracted and disappeared along the Japanese coast
from the Tsushima Strait to the western Tsugaru Strait,
and reappeared in northern areas off the Hokkaido
coast. Although the fishing areas in August generally
resembled those in July, the fishing area along the
Hokkaido coast disappeared in August. September
saw an increase in fishing areas, especially around the
Yamato Rise, the east coast of Korea and Japanese
waters from Tsushima Strait to the Oki Islands. Note
that September fishing areas spread continuously from
Ulleung Island to the western Tsugaru Strait and
across the Yamato Rise.
In October and November, fishing areas formed 2
distinct areas. One area formed around Korea’s eastern
coast and spread to the Yamato Rise, as in September;
the other in the north above latitude 42°N. By
November, the October fishing areas around Ulleung
Island and Yamato Rise formed a dense aggregation
from the southern edge of the Yamato Rise to the Oki
Islands. In December, the main fishing areas formed
along the east coast of Korea and near the Oki Islands
(Fig. 8). No fishing area was recorded farther north
than about latitude 40°N. Fishing areas along the latitude
40°N line stretched from Ulleung Island to off the
coast of Japan.