Assessment of Metal Accumulation and Bioaccumulation Factor of Some Trace and Heavy Metals in Freshwater Prawn and Crab

Globally, freshwater decapods have been one of the major food delicacies because of their rich deposits of minerals. High metals are usually accumulated in the body tissues of these organisms because of their lifestyle. Metal accumulation in freshwater decapods has been acclaimed and perceived to cause serious health concerns when transferred to humans along the food chain. A recent study has shown that freshwater biota, prawn ( Macrobrachium rosenbergii ), showed significant differences (p < 0.05) in Mn, Cu, Pb and Cr and no significant difference (p > 0.05) in Fe, Zn and Cd. In contrast, the freshwater biota, crab ( Sudanonautes africanus ), showed significant differences (p < 0.05) in Fe, Zn and Mn and no significant differences (p > 0.05) in Pb, Cr and Cd. A high accumulation of Fe in the whole tissues of Macrobrachium rosenbergii and Sudanonautes africanus was also established. This is because Fe in the Nigerian soil and sediment is naturally very high beyond slated thresholds and tend to accumulate and transcend or magnify in benthic. It was noticed that Zn (2.68) and Cr (4.52) had the highest bioaccumulation factors in prawn and crab, respectively. Chromium has been observed to be carcinogenic. The consumption of Cr in the muscles of crab might constitute probable serious health risk.