ASSESSMENT OF HEAVY METAL BIOACCUMULATION IN THE GILLS AND TISSUE OF THE JUVENILE CLARIAS GARIEPINUS (CATFISH)
The Assessment of heavy metal Bioaccumulation as well as the rate of excretion of the bioaccumulated metals in the Gills and Tissue of the juvenile Clarias gariepinus (catfish) when placed in pollution-free aquatic environment (artificial environment) was determined. Clarias gariepinu (catfish) samples of about ten weeks old were collected from fish tanks in the Department of Environmental Zoology of the Delta State University, Abraka and held in bulk container filled with chlorine-free water for five days at 28?20C. While preparing the stock and test solutions for the metals, the nitrate form of lead, chloride of cadmium and the zinc sulphate (ZnSO4.7H20) were chosen because of its moderate toxicity. Bioassay test method was adopted with three different concentrations of the test solutions (10 mg/kg, 5 mg/kg and 2 mg/kg of lead, 8 mg/kg, 5 mg/kg and 2 mg/kg of cadmium and 8 mg/kg, 5 mg/kg and 2 mg/kg of zinc) of the metals under investigation were prepared. The Cappon (1987) Static method was used in digesting the fish sample and metal concentration in the gills and tissues of the fish samples were determined using Atomic Absorption Spectrophotometer. Results from this study revealed that Pb had a higher mortality rate (20%) than cadmium (10%) and zinc (0%) at the same concentration of 5mg/kg. The study further revealed that the bioaccumulation of heavy metals in the different parts of the fish was not uniform but could thus, be concluded that the determination of bioaccumulation can be used to monitor the health of aquatic environment as data from the study revealed that the degree of contamination was directly proportional to bioaccumulation. Results obtained from this work also indicated that if fish exposed to contaminated environment are able to migrate to safe unpolluted environment, they can, over a period of time naturally eliminate significant amount of ingested toxicants such as heavy metals.
|Keywords: bioaccumulation, bioaccumulation factor (baf), heavy metals, clarias gariepinu, juvenile, catfish|
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