ABSTRACT
The water around Jeju Island was characterized by the Tsushima warm current (TWC) being high temperature and salinity and the Yellow sea cold bottom water (YSCBW) being low temperature and salinity We investigated the diversity indices, community structures and trophic level of fish species collected by trawl net in the waters around Jeju Island during April 2004-August 2005. We also presented ecosystem structure estimated by combination of trophic level and the oceanographic condition. There were totally distributed 301 species in the survey area during April 2004-August 2005, regionally 151-229 species in TWC and 75-154 in YSCBW. Shannon's diversity indices (H') of TWC were 2.95-3.39, being higher than those of YSCBW (2.11-2.40), and species richness (R) of TWC were 10.93-18.33, being also higher than those of YSCBW (6.96-12.48), except the values of October 2004. A total of 7429 individuals of 98 species was seasonally examined for their dietary composition in the survey area during 2004-2005. Of which, 3,682 individuals were observed with prey organisms. Standardized diet composition and trophic level estimates were calculated for predators in the survey area being influenced by TWC and YSCBW Trophic level values were diverged with range from 3.23 of the small pelagic to 4.39 of the goose fish, depending on the taxonomic group. The analysis of trophic level values showed that ecosystem structure was different between TWC and YSCBW during April 2004-August 2005.