Assessment of bacterial loads of Clarias gariepinus (Burchell, 1822) obtained from cultured and natural habitats

Abstract

Abstract Background African catfish (Clarias garipienus) is a major tropical aquaculture species in Africa and most cultivated by fish farmers in Nigeria. The dominance of African catfish for fish farming is attributed to several favourable characteristics such as its ability to tolerate a varying range of environmental conditions, high stocking densities under culture conditions, fast growth rate, acceptability of artificial feed, high fecundity rate, ease of artificial breeding and high market value. However, catfishes are known to harbour bacteria which limit its suitability for human consumption. Hence, this study was conducted to compare the bacterial loads of C. gariepinus from cultured and natural habitats. Methodology A total number of twelve live adult (200–799 g) C. gariepinus comprising 3 each were randomly obtained from two cultured habitats (ponds) and two natural habitats (rivers). In the laboratory, the skin and the intestine of the fish were examined for the presence of bacteria using nutrient, mannitol salt and cetrimide agars. Results Seven bacteria isolates namely, Pseudomonas aeruginosa, Bacillus subtilis, Staphylococcus aureus, Staphylococcus epidermis, Micrococcus luteus, Escherichia coli and Streptococcus spp. were identified from the catfishes using their colonial, morphological and biochemical characteristics. The results showed that the total bacterial loads in cultured habitat (skin, 25.77 × 104cfu/g; intestine, 22.50 × 104cfu/g) were significantly higher than the total bacterial load recorded in natural habitat (skin, 15.94 × 104cfu/g, intestine, 14.23 × 104cfu/g). Specifically, total Staphylococcal loads (skin, 10.40 × 104cfu/g; intestine, 10.77 × 104cfu/g) and Pseudomonad loads (skin, 6.80 × 104cfu/g; intestine, 8.00 × 104cfu/g) were significantly higher in cultured habitat than natural habitat where Staphylococcal loads (skin, 6.66 × 104cfu/g; intestine, 5.50 × 104cfu/g) and Pseudomonad loads (skin, 5.46 × 104cfu/g; intestine, 5.54 × 104cfu/g) were recorded. Generally, it was observed that bacterial loads were higher on the skin compare to intestines of C. gariepinus obtained from both habitats. Conclusion The study showed that bacterial loads were more in C. gariepinus obtained from cultured habitat compared to those obtained from natural habitat. It is therefore recommended that sanitary conditions under which fish are reared in fish pond should be improved.

Keywords

• Bacteria loads
• Clarias gariepinus
• Isolates
• Ponds
• Rivers