Experimental Investigation of Some Heavy Metals in the Muscle Tissue of Cultured African Catfish (Clarias gariepinus)

Abstract

Often times, environmental scientist believes that heavy metal contamination of aquatic ecosystem is related only to fishes in aquatic environment. The present study was therefore undertaken to investigate the bioaccumulation of Manganese (Mn), Cobalt (Co), Mercury (Hg), Asernic (As), Chronium (Cr) and Nickel (Ni) in the muscle tissue of Cultured African Catfish (Clarias gariepinus). A total of two (2) fish were used (male and female) weighing 390g and 310g. They were sacrificed and all the internal organs were removed and was oven dried at initial temperature of 1050c and later adjust to 650c until a constant weight was obtained. The samples were grinded and were digested with tri acid mixture (HNO3: HCL: H2SO4). Digestion continued until the liquor become clear. The samples were analyzed using Dez Elmer Analyst 300 Atomic Spectroscopy (AAS). The result showed that Mn recorded 896.94±0.577mg/l; Co 78.10±0.577mg/l; and Ni, 78.725±0.578mg/l in feed 1 and Mn recorded 506.823±1.155mg/l; Co 32.499±0.577mg/l; Hg, 0.001±0.00001mg/l; As, 0.006±0.0000mg/l; Cr, 122.794±0.577mg/l. and Ni 56.180±0.578mg/l in feed 2. The result of the muscle tissue of male and female C.gariepinus shows the presence of heavy metals at different concentrations and the highest concentration was observed in female recorded Ni (44.200±0.5774mg/l) and the lowest observed in males recorded in Cr (-0.007±0.0001mg/l). There was a significant difference (P>0.05) among male and female C.gariepinus. This study has proved the availability of Mn, Co, Hg, As, Cr and Ni in the muscle tissue of C.gariepinus and also in the water and feeds used in culture the fish. This metal concentration observed in muscle tissue feeds and water was beyond the maximum permissible limit by WHO/FAO and NOAA for human consumption contrary to the most view that bioaccumulation of heavy metals is related to environmentally polluted water. Based on these findings, it is recommended that proper quality control analysis should be carried out in the cultured fish to determine its safety.