Image classification and signature-separability
analysis
Image classification identified 7 different areas of
temporal variability in fishing-vessel distribution.
Table 2 illustrates the results of the signature analysis.
The average distance was 1.4, indicating high separability,
i.e. that the 7 fishing areas were successfully
identified to class. The 7 classes have distinct spatial
patterns (Fig. 9) and represent different months
(Fig. 10).
Class 1 (Fig. 9) was located around latitude 41°N,
extending from north Korean waters and the Hokkaido
coastline to the Yamato Rise. Class 1 was also seen in
the northern part of the Sea of Japan. Class 1 fishing
areas appeared from August to September (Fig. 10).
Class 2 (Fig. 9) was located around Ulleung Island,
Cheju Island, and the coast of Hokkaido, with the
largest areas near Ulleung Island. Class 2 occurred in
January and continuously from May to December
(Fig. 10). Taking into consideration the mean DN and
the locations of the fishing area, fishing area occurred
mainly from July to December. Spatial patterns of
Class 3 (Fig. 9) were similar to those of Class 1; vessels
were identified around latitude 40°N, from the Korean
coastline to the Yamato Rise and along the western
coast of Hokkaido. However, temporal variability differed
from that of Class 1, as Class 3 fishing areas were
recorded from May to November (Fig. 10). Class 4
(Fig. 9) followed the Japan coast from the Oki Islands
to northern Honshu, with none identified in Korean
waters. Class 4 fishing areas developed from April to
June, as well as in December (Fig. 10). Spatial distributions
of Class 5 (Fig. 9) extended from southwest of
Tsushima Island to latitude 37°N, along the coast of
Korea, to the Oki Islands along the Japanese coast.
Fishing areas were recorded in all seasons (Fig. 10).
Class 6 (Fig. 9) had the largest distribution of all the
classes, extending between the Oki Islands and Yamato
Rise and into northern parts of the Sea of Japan.