Comparison of fish fauna in three areas of adjacent eutrophic estuarine lagoons with different salinities

Variation in fish assemblages was investigated to clarify the migration pat terns and growth rates of marine, brackish and freshwater species in three adjacent areas with different salinities. In the polyhaline Lake Nakaumi, J apan, benthic fishes and crustaceans were negatively affected by oxygen dep letion in the lower water under stratification during the warm seasons. On the other hand, marine and brackish species that once migrated into the Hon jo Area, which is isolated from L. Nakaumi and has a homogeneous salinity s tructure, remained and grew there until winter. In the mesohaline Lake Shin ji, two types of fishes were distinguished: one that migrated into the lake during the warmer seasons; and the other which stayed in the lake during w inter. Fauna and production in L. Shinji were compared with those of a comp rehensive study carried out approximately 35 years ago. For 35 years, Konos irus punctatus and Sardinella zunasi have increased in abundance, while Car assius sp. and Hypomesus nipponensis have decreased, Even with the recent a cceleration in eutrophication of the lake, fish production during the warme r seasons has not declined for 35 years, but the fish fauna have drasticall y changed. (C) 2000 Elsevier Science B.V. All rights reserved.