内湾および干潟における物質循環と生物生産【59】播磨灘2.魚種間関係と環境変化からの検討

摘要

The catches of plankton feeder occupied the 75% of the total fish catches. The plankton feeder except sardine showed the peak of 55 thousand ton of catches near at 1969 and decreased since then and to thirty thousand ton at 2005. The catches of flat fish was peak at 1965, 1978 and 1997. Since the peaks were coincidence of the one of launce, anchovy and sardine, the flatfish was thought to be related with plankton feeder. It is found that a reclamation areas is related to the catches of short-necked clam, flatfish and shrimp. It is speculated that the reclamation decreased the shot-necked clam then phytoplankton is not used by the clam then unavailable phytoplankton invokes oxygen deficiency. In the result, flatfish and shrimp is thought to be damaged. The decrease of fish catch may be due to the decrease of the land based inputs of nutrients such as nitrogen and phosphorus (poor nutrient). It is discussed whether the poor nutrient produced the decrease of fish catch in Seto Inland Sea.