瀬戸内海東部（播磨灘）の栄養塩環境と漁業

摘要

Red tides were frequent, and eutrophication went ahead in the Harima-nada of the early 1970s. Various environmental measures were performed, and the sea became clean afterwards. However, discoloration of cultivated "Nori" occurs because in late years dissolved inorganic nitrogen (DIN) became too much low. In addition, the fishery production decreases to a half of the early 1990s. Therefore, a decline of the production capacity of the sea by the decline of the nutrient is concerned about. From the reason, we analyzed it about fish catches and relations with the DIN. As a result, meaningful correlation was seen between DIN concentration and fish catches of the compact trawl. In addition, it was thought that the DIN concentration was affected by the load from the land. From these results, we supposed that fish catches decreased by a decrease in load from the land.