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This study used Defense Meteorological Satellite Program (DMSP)/Operational Linescan System (OLS) satellite images to classify and analyze the spatial and temporal variability of nighttime fishing vessel lights in the Sea of Japan. OLS images can detect the powerful lights used to attract squid. We examined DMSP/OLS nighttime visible images from 1994 to 1999. Fishing areas of the Japanese common squid Todarodes pacificus were defined as the bright areas created by 2-level slicing methods on DMSP/OLS images. T. pacificus fishing areas were mainly found along the east coast of Korea, between Cheju and Tsushima Islands, around the Yamato Rise, along the coast of Honshu, and in northern areas of the Sea of Japan. Using image classification and separability analysis, we divided the Sea of Japan into 7 areas based on different temporal variability in squid fishing area characteristics. The classification takes the potential northern and southern squid migration patterns into account. One of the potential northern migration patterns formed along Honshu Island to the north; another appeared along the east coast of Korea, northward through Yamato Rise. Southern migration patterns were almost the reverse of northern migration patterns. These 7 classified areas also correspond to the oceanographic characteristics of the Sea of Japan, i.e. a polar front at latitude 40°N, the inflow of the Tsushima Warm Current (TWC), and warm eddies. The use of remotelysensed data demonstrated in this study offers a powerful and innovative way in which to determine the migration and ecology of the Japanese common squid.

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a b s t r a c tEnergy intake during the northward migration of tagged juvenile skipjack tuna (Katsuwonus pelamis) was estimated using the heat increment of feeding (HIF) determined through peritoneal cavity temperature data acquired with an archival tag. The effectiveness of this method was confirmed by feeding experiments, even in a species without visceral heat exchangers. Applying these experimental results to the data from tagged fish in the wild revealed that the estimated energy intake of skipjack tuna was, on average, 2.2 times greater in temperate waters than in subtropical waters. This difference was likely due to the differences in the food supply between habitats. In contrast, the estimated energy cost of their daily travel distance decreased with northward migration. This result suggests that skipjack spend less energy in acquiring prey in temperate than in subtropical waters since prey are available in higher densities, thereby providing excess energy for growth or lipid reserves.

SUMMARY: In Todarodes pacificus, recruitment success is most likely dependent on the physical and biological environments of the spawning and nursery grounds. Annual catches of T. pacificus in Japanese and Korean waters have markedly increased since the late 1980s and the recent catch is equal to that of the 1960s. Here re proposed is a possible scenario for the stock increase since the late-1980s based on GIS analysis of changes in the inferred spawning area during 1984-1999. This study suggests that winter-spawning areas in the East China Sea shrank when adult stocks decreased during a cool regime, and that fall and winter spawning areas extended and overlapped in the Sea of Japan and East China Sea when adult stocks increased during a warm regime. We conclude that stock fluctuations in T. pacificus occur with annual changes of winter-spawning areas related to climatic regime shifts.