Changes in fish and crustacean assemblage in connected coastal lagoons, Lake Nakaumi and Lake Shinji, Japan.

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Fish and crustacean assemblages in Lake Nakaumi (2 Stas.) and Lake Shinji (1 Sta.) were investigated using set nets monthly from April 1995 to March 1997. During 2 years 69 and 65 fish species were recognized in Lake Nakaumi (except for the Honjo Area) and Lake Shinji, respectively. The annual manner of the appearance and growth for each fish and crustacean was similar at each observational station. However, the monthly catches for each fish and crustacean were largely different between the 2 years. We found that a large portion of fish catches was not commercially utilized, and not counted for fishery statistics.<BR>Numbers of fish species in Lake Nakaumi had markedly decreased compared with the 103 species reported by Miyadi (1962). In western Lake Nakaumi, the growth of crustaceans was affected by oxygen depletion in the lower layer of water during warm seasons, and the catch of Hypomesus transpacificus nipponensis in winter decreased to near zero. The environment for fishes and crustaceans in Lake Nakaumi worsened due to the promotion of closurity and the deterioration in aquatic habitats. The present standing crops of major fish species in Lake Shinji were estimated using the method of Miyadi (1962) and the results of this study. Despite the recent advance in eutrophication, the high productivity of fishes was still maintained. However, fish fauna had largely changed to plantivorous species in Lake Shinji.
日本陸水学会の論文