A comparative study of various ecological factors of the Pulicat Lake in relation to fishery during a severe drought season in 1975 and a normal season in 1976 is presented. High salinity and temperature condition has affected the plankton production, whereas very low oxygen level has resulted in heavy fish mortality during the closure period of the bar mouth of the lake. For improving the fishery, keeping the present bar mouth permanently open and establishing another connection with the sea at the northern end of the lake are suggested.