Abstract: The discharge of xenobiotic substances like heavy metals into the aquatic systems has deleterious effect on the aquatic organisms including fishes. The present study was designed to see the subtoxic effect of nickel on the fish Channapunctatus. The protein, glucose and cholesterol content of tissues from liver, kidney, brain and ovary were analysed. The alternations in protein contents of all the tissues are significant in the level 0.001in 40ppm nickel concentration. There was significant increase in glucose and cholesterol concentration of all the tissues in between the level 0.001 to 0.01 on exposure to in 40ppm nickel concentration in all the tissues. The lipid and protein content decreased in 40ppm in all the four tissues (0.001 to 0.05 level of significance). These significant alterations in the biochemical parameters of various tissues of Channapunctatus indicate deleterious effect of nickel exposure at subtoxic level also.