The Fluctuation in the avundance and species composition of fish was investigated Sorido Island southern, Korea from August, 1999 to May, 2000. A total of 1,920.6 fishes were sampled and classified into 9 orders, 34 families, and 39 species. The dominant order were Perciformes including 15 famailies and 17 species, followed by Pleuronectiformes including 5 families and 6 species, Scorpaeniformes including 4 families and 6 species Ilisha elongata was the dominant occupying 23.96%, followed by Scomber japonicus 16.27%, and Engraulis japonicus 10.98%. Year-round species dominant occupying Conger myriaster, Ilisha elongata, Platycephalus indicus, Leiognathus nuchalis. Seasonal species occupying Hapalogenys mucronatus, Uranoscopus japonicus, citharoides macrolepidotus. The monthly diversity, evenness, and Richness index were 1.970~2.528, 0.669~0.759, 2.747~4.729, respectively.