Drastic Decreasing of Annual Catch Yields of the Manila Clam Ruditapes hilippinarum in Ariake Sound, Southern Japan.
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概要
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Ariake Sound, southern Japan, has a huge area of tidal flats where the clam Ruditapes philippinarum is one of the major fishery products. This is also true of Kumamoto Prefecture bounding the Sound. In the past, annual catch yields of the clam in Kumamoto occupied over the half of the total catch yields of the clam in Japan. Although it reachied a peak of 65.5×10<SUP>3</SUP> ton in fiscal year (FY) 1977, the catch drastically decreased in FY 2000 to about 1% of the maximum catch year. This is also true of the other clams important commercially to the sound. Total catch yields of R. philippinarum in Japan reached a peak of 140-160×10<SUP>3</SUP> ton per year in FY 1975-1987, and then showed drastic decreases of the yields. Preliminary analyses of annual catch yield statistics of the clam in all Japanese regions indicate that the cause of decreasing yields may be different depending on fisheries regions, that is, the causes in Kumamoto may be shared with those of other prefectures bordering Ariake Sound, though the causes for R. philippinarum within the Sound may be different from those for other clams important commercially to the Sound. On the bases of analyses of historical data on annual catch yields of R. philippinarum and environmental conditions in the Sound and on several studies dealing with larval recruitment processes as determinants of benthic population size of the clam, one of the causes may be higher larval mortality, rather than decrease of spawning stocks due to overfishing. Short- and long-term studies are proposed in order to identify the causes for R. philippinarum in the Sound and also to make clear mechanisms by which the clam populations may be maintained.
- 日本海洋学会の論文
日本海洋学会 | 論文
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