Parasitic diseases and heavy metal analysis in Parachanna obscura (Gunther 1861) and Clarias gariepinus (Burchell 1901) from Epe Lagoon, Lagos, Nigeria

ObjectiveTo evaluate the bioaccumulation of heavy metals in Parachanna obscura (P. obscura) and Clarias gariepinus (C. gariepinus) and the use of their parasites as accumulation indicators from Lekki Lagoon.MethodsSamples of fish were procured from Oluwo market, a landing site of fish of artisanal fishermen in Epe. Metal accumulation, and intestinal parasites and protozoan of P. obscura and C. gariepinus were investigated. Sediment and water samples were examined for selected heavy metals (Cu, Cr, Ni, Pb and Fe) while nematode parasite from infected fish were also analysed for heavy metal content.ResultsAbsolute morphometric parameters had low correlation with single independent morphometric index (total length and standard length) but increased when correlated with combined indices. The prevalence of parasitic infections in P. obscura and C. gariepinus were 35% and 36% respectively. The metal concentrations accumulated in the fish's liver were more than that found in the water and sediment. There was strong correlation in metal accumulated in the parasites relative to the water medium (r = 0.968 – 1.000, P < 0.01). Procamallanus spp., a nematode accumulated 2 times more Cu, Cr, Ni, Pb and Fe than Wenyonia sp. There was higher heavy metal level observed in intestinal nematode Procamallanus sp. than wenyonia sp. in the infected fish in this study.ConclusionsThis suggests that Procamallanus sp. may be used as a potential sink of metal pollution in an aquatic environment and also a good sentinel in the environment.