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Fluctuations in fish catch of middle-sized pelagic fish in the Seto Inland Sea, Japan
H. Hashimoto, T. Shibuno, S. Ishikawa and K. Gushima

Catch fluctuations of middle-sized pelagic fish such as sardine, anchovy, young clupeoid fish (juvenile sardine and anchovy) horse mackerel and mackerel in the Seto Inland Sea were analysed from 1964-’91. Since 1975, the sardine catch rapidly increased and became the most dominant catch from 1978-’82, whereas catches of the other fish decreased. From 1983-’86 the sardine stock decreased gradually, while catches of the other fish recovered. Recently, however, the anchovy catch has decreased again whereas catches of young clupeoid fish have fluctuated sharply at high levels. The connection between fish catches and environmental factors (water temperature, salinity, COD and chlorophyll-a) was examined. However, no correlation between trends in catch and environmental factors was found. It is said that the pelagic fish form their own community and competition occurs between fish in that community. Although the sardine were not distributed typically in the sea, the recent increase in abundance due to migration from the Pacific Ocean has affected the structure of the pelagic fish community. Consequently, the relative abundances of the pelagic fish may have influenced the composition of the catches. The increase in the catch of young clupeoid fish in recent years may have resulted from sardine spawning in the sea.

Keywords: Middle-size pelagic fish, the Seto Inland Sea, catch fluctuation, sardine, anchovy, horse mackerel, mackerel, clupeoid fish.
Contents of this volume Sci. Mar. 59(3-4) : 499-506 Back PDF
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