CHANGES IN FISH SPECIES-DIVERSITY AND DOMINANT SPECIES COMPOSITION INTHE YELLOW-SEA

Species diversity of the Yellow Sea fish community in 1959, 1981, 1985 and 1986 was measured by means of several methods. An evenness index, E=log(e)(1/lambda)/log(e)S, was introduced to measure the fish commun ity. The differences in diversity index in the Yellow Sea between seas ons are due to fish migration, while the differences between years are attributed to the changes of species composition caused by overfishin g and species interactions. The numbers of dominant, common and rare s pecies of fish were calculated using Hill's diversity index. The domin ant species in 1959 were all demersal fish, which were the major targe t for fisheries in the 1950s and 1960s. However, in the 1980s, pelagic fish took a very dominant position, especially small pelagic fish, wh ich were the prey of large pelagic and bottom fish. This indicates tha t the depletion of most demersal fish and large size pelagic fish has resulted in the increase of small planktophagous pelagic fish in the Y ellow Sea.