Monthly fish samples were collected using bottom gill nets and analyzed to study species composition and seasonal variation of fish assemblages in the coastal waters off Gadeok-do, Korea in 1998. During the study period, a total of 49 fish species representing 30 families were collected. The fish assemblages predominantly consisted of Limanda yokohamae, which accounted for $53.3\%$ of the number of individuals and $42.2\%$ in the biomass. The fish species, which had over 100 individuals, included Cynoglossus abbreviatus, Ditrema temmincki, Hexagrammos otakii, and Stephanolepis cirrhifer. These four species accounted for $24.1\%$ of the number of individuals and $24.3\%$ of the biomass. More fish species were collected in May and June than in any other months. The number of individuals and the amount of biomass peaked in April and May and reached a low in August. While the predominance of L. yokohamae caused the lowest species diversity by number of individuals in April, the predominance of Platycephalus indicus caused the lowest species diversity by biomass in July. Although gill nets show a strong selectivity for the target species or for size, gill nets can be used as an alternative fishing gear to collect fish in waters with rough bottoms, like rocky reefs, where other kinds of fishing gear such as trawls can not be used.