Heavy metals and polycyclic aromatic hydrocarbon content of cultured Clarias gariepinus (Cat Fish) muscle and pond water in Lagos Metropolis, Nigeria

Abstract

Background: The quest to meet growing demand for fish and economic sustenance has led to increased number of aquaculture farms in Nigeria with little consideration on the biochemical and environmental status of the fishes.

Objective: This study investigated the heavy metals, polycyclic aromatic hydrocarbons (PAHs) haematological, antioxidant and biochemical status of cultured Clarias gariepinusand its pond water.

Methods: Muscle tissues excised from C. gariepinus and pond water samples obtained from commercial fish ponds across five locations (Akoka, Surulere, Ejigbo, Iyana Ipaja and Badagry) within Lagos State, Nigeria were evaluated for heavy metals, polycyclic aromatic hydrocarbons (PAHs), and antioxidants content using Atomic Absorption Spectrophotometer, Gas Chromatography, and  spectrophotometric methods respectively. Haematological and some biochemical parameters were determined in blood samples collected from the fishes.

Results: Heavy metals and PAHs detected in the fish muscle and pond water samples were at concentrations significantly (p<0.05) above standard permissible limits. The order of prevalence of heavy metals in the C. gariepinus muscle and pond water was Ni > Pb > Cr > Cd. Significant (p<0.01) positive associations exist between antioxidant biomarkers (SOD, CAT and GSH) and lipid peroxidation biomarker (MDA). However, there was no significant (p>0.05) difference in the levels of haematological, lipid profile and kidney function biomarkers of the C. gariepinus cultivated across all the five locations.

Conclusion: Present study show evidence of pollutants in the fish muscle and therefore call for adequate monitoring to ensure the safety of the food chain especially with the up springing of local fish farms across Lagos, Nigeria.

Keywords: Biosafety, Clarias gariepinus, Food chain, Heavy metals, Polycyclic aromatic hydrocarbons