In order to investigate the oceanic condition of fishing ground in the southwestern coastal sea of Korea, the oceanographic observation were carried out by the trainingship of Yosu university on May, August and November in 1998. Main features in the observation are as follows; 1) the ranges of temperature, salinity, density and chlorophyll-a were from $14.5^{circ}C;to;18.0^{circ}C,; from;33.5 extperthousand;to;34.5 extperthousand$from 24.0 to 25.5 and from $1.0mu$g/l in spring (May) from $15.0^{circ}C;to;27.5^{circ}C,;from;0.0 extperthousand;35.0 extperthousand$9.0 to 26.0 and from 0.5$mu extrm{g}$/l to 4.0$mu extrm{g}$/l in summer(August), and from $ to 21.0^{circ};31.0 extperthousand$, from 22.0 and from $4.0mug/l;to;20.0mug/l$ in autumn(November), respectively, 2) the temperature in the coastal region was higher than that in the open ocean while salinity, density and chlorophyll-a were lower, and the convection was identified between the surface and the bottom during in spring and autumn, 3) the chlorophyll-a in the this region was varied in each season, being highly distributed offshore Yosu Bay, 4) on evidence of sea water intrusion toward Kumun island was observed.