Effectiveness of hatchery-reared Japanese flounder (Paralichthys olivaceus) in the coastal waters off Kanagawa prefecture [Japan]
2008
Isshiki, T.(Kanagawa-ken. Fisheries Technology Center, Miura (Japan)) | Katayama, S.
Japanese flounder (Paralichthys olivaceus) is an important coastal fisheries resource in the coastal waters off Kanagawa prefecture. The main fishing gears were gill net and set net in the Sagami Bay and the mouth part of Tokyo Bay and small bottom trawl net in the inner part of Tokyo Bay. The catch commenced to decline in the late 1970's and fell to the bottom in the end of 1980's. In recent year, however, it has been relatively stable after recovering in 1990's. The stock enhancement program of the flounder has been carried out in Kanagawa prefecture since 1987. Approximately 95-325 thousand hatchery-product juveniles (60mm and over in mean total length) were released every year from 1992 to 2004. Ratio of released fish in the landings and return rate were estimated to be 25.9-81.9% and 4.5-12.5% (7.2% on average) in the inner part of Tokyo Bay, while 8.1-23.0% and 1.8-9.7% (5.0% average) in the Sagami Bay and the mouth part of Tokyo Bay. Age composition in the, Sagami Bay and the mouth part of Tokyo Bay showed more occurrences over 2 years old of wild flounder than released fish, suggesting possibility of immigration of wild fish from other sea areas.
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