The tissues were homogenized and approximately 10gm of the homogenate then digested as follows 1.0 gm of the powdered samples (muscle, liver and gill) were placed in a 100 ml round bottom flask with ground glass joint and mineralized under reflux using a mixture of 6 ml HNO3, 2.0 ml HClO and 4 ml H2O2 . The digestion is done with help of water bath .The digestion procedure lasted for about 6 h to obtain a clear solution. The digests were prepared in triplicate and carefully transferred with their respective washing into a 25 ml volumetric flask and diluted to volume. The digests were then analyzed for Cu, Cr, Pb and Zn, using an atomic absorption spectrophotometer (MODEL No. SL 173, ELICKO, India) with aqueous calibration standards prepared from the stock standard solutions of the respective elements as was reported by