Microbiological Quality, Proximate Composition and Heavy Metal Contamination of Pond-raised Catfish (Clarias gariepinus)

Abstract

Catfish (Clarias gariepinus) is a commonly consumed fish in Nigeria. Its high demand necessitated fish farming in ponds which is now the current trend for fish production in Nigeria. Thus, the safety and quality of pond raised catfish has to be ascertained. The nutritional content, microbiological quality and heavy metal contamination of twenty (20) pond-raised catfish purchased from four different markets in Lokoja, Nigeria was determined using standard laboratory methods. The total bacterial count ranged between 1.5 x 103 - 3.9 x 103 cfu/g while the total fungal count ranged between 1.0 x 103 - 2.2 x103 cfu/g from the different sampling locations. The fungi from the pond raised fish samples were identified as Rhizopus stolonifer, Aspergillus niger, Mucor sp., Penicillum sp. and Fusarium sp. The bacterial isolates were identified as Escherichia coli, Micrococcus sp., Salmonella sp., Staphylococcus aureus, Proteus sp., Bacillus sp., and Pseudomonas sp. Iron (Fe), copper (Cu), nickel (Ni), zinc (Zn) were present in all the fishes examined at concentrations not exceeding the approved permissible limits in food although lead (Pb), and cadmium (Cd) were below detection limits in all the fish samples. Pond raised catfish is a rich source of protein and fat. The incidence of some likely enteric and toxigenic organisms in the fish calls for a systematic approach in ensuring safety of the consumers. The consumption of the fish does not pose a likely source of heavy metal accumulation however the source of zinc in the fish should be identified as they can bio-accumulate quickly and pose a serious health risk to man.