Predisposing Factors that Promote Prevalence of Heavy Metals Assimilation and Bioaccumulation in Aquatic Medium and amongst Fishes

The degree of heavy metals assimilation and bioaccumulation in fish tissues (muscles, gills, liver, and kidneys), amongst scale-less fishes- Chrysichthys macrotis, Chrysichthys nigrodigitatus, Clarias gariepinus and Heterobranchus longifilis, -scaly fishes- Cynoglossus senegalensis, Oreochromis aureus, O. niloticus, Lutjanus fulgens, Pomadasys rogeri, and Tilapia galilea, water columns and sediments, were investigated. Heavy metals assimilation and bioaccumulation varied among organisms with or without scales, tissue types, and fish location (water column & sediments) and pollution level.  Fishes with scales had lower concentrations of heavy metals than scale- less fishes. The scalier the fish, the lower the metal assimilation and bioaccumulation. As expected, trace metals were generally lower in muscles than liver, and kidney. Liver had highest followed by kidney, gills and then muscles. Fish trophic level (water column or sediments) and water pollution levels affected heavy metal concentrations. Concentrations were always more in sediments than water column or tissues. The more polluted the water, the more the assimilation and accumulation of trace metals.