Bacterial flora of polycultured common carp (Cyprinus carpio) and African catfish (Clarias gariepinus)

Quantitative and qualitative analyses of bacterial flora associated with pond water, gills, and intestine of polycultured healthy common carp (Cyprinus carpio) and African catfish (Clarias gariepinus) were carried out and identified to species level where possible. Total viable bacterial counts in the pond water ranged from 9.2 ± 5.5 × 103 to 6.6 ± 5.1 × 104 colony-forming units (cfu)/mL; in the gill filaments of carp and catfish, 3.3 ± 3.8 × 106 to 7.9 ± 5.6 × 106 and 1.1 ± 4.6 × 105 to 2.3 ± 5.2 × 106 cfu/g, respectively; and in the intestine of carp and catfish, 1.4 ± 2.9 × 1010 to 1.7 ± 6.0 × 1011 and 2.7 ± 3.4 × 1010 to 1.0 ± 4.5 × 1011 cfu/g, respectively. Gram-negative rod-shaped bacteria dominated the populations: 90% in carp, 89% in catfish, 80% in water, and 86% in the total populations. Altogether, 14 bacterial species of 10 genera were identified in total populations. Pond water bacteria had a reflection on the bacterial composition of the gills and intestine of carp and catfish. Aeromonas hydrophila, Shewanella putrefaciens, Vibrio cholerae, Staphylococcus sp., and Vibrio vulnificus appeared as the common bacteria in the populations, where the first three were highly significantly abundant (P<0.0001). Moreover, A. hydrophila was the most significantly dominant bacteria (32%; P<0.005) among the total populations. Pantoea sp. and Pasteurella pneumotropica were present only in carp and catfish, respectively, but Corynebacterium urealyticum and Micrococcus sp. were present only in pond water.