29. Fisheries, Utilization, and Stock Status of Spiny Dogfish in Japan
Hideki Nakano, Yasuko Semba, and Daiji Kitagawa
Abstract.—Around Japan, spiny dogfish Squalus acanthias occur off the Pacific coast of Hokkaido Island and northern Honshu and off the western coast of Japan from the East China Sea to the Japan Sea. They have been caught and used historically on both coasts. This species is usually caught as bycatch except in some small-scale local fisheries which directly target it.
The spiny dogfish is known to migrate widely according to seasonal patterns. Individuals living off Honshu (both coasts) during winter migrate north along the preferred thermocline (assumed 8–12°C) in spring and summer, and individuals off Hokkaido move south following the preferred water temperature in autumn and winter. The migrating schools mainly consist of mid- to large-size fish of about 80 cm. Small fish, less than 50 cm, are believed to remain in localized areas and do not migrate.
Spiny dogfish catch became important in the early 1900s as subsidiary fisheries resources for bottom longline fishing vessels targeting Pacific cod Gadus morhua or halibut Hippoglossus stenolepis in northern part of Japan. After that, the fishery repeatedly expanded and contracted during 1910–1920 depending on the price of fishmeal fertilizer. Industrial bottom trawl fishing was introduced to the spiny dogfish fishery in the 1930s. After World War II, the spiny dogfish catch rapidly increased with the support of a policy of increasing food production yields. The total shark landing of Japan was about 50,000 metric tons (mt) in 1947, but it rapidly increased to 120,000 mt in 1950. Catch then decreased for economic reasons and has remained at low levels. At present, industrial bottom trawl, bottom longlines and gill nets have been the primary gear used for fishing spiny dogfish. The longline and gill net gear, which target bottom and floating fish, respectively, were primarily used in northern areas, whereas industrial trawling occupied an important role in the fishery in southern areas.
Given global concerns regarding the stock status of sharks and the lack of conservation strategies for non-target species, the Japan Fishery Agency established an advisory committee for a National Plan of Action (NPOA) for the Conservation and Management on Sharks in 1997. The Fisheries Agency established a formal National Plan of Action in 1999 with the cooperation of the Advisory Committee. Status assessments of sharks are made every 2 years and recommendations for conservation and management are given based on the assessment report.