Microbial flora of Clarias Gariepinus in the early stages of Development

A study was carried out to establish the microbial flora in farmed Clarias gariepinus hatchery systems. Enumeration of total aerobic heterotrophic bacteria and fungi, total coliforms, Salmonella spp. Vibrio spp. and Aeromonas hydrophila from eggs (fertilized and unfertilized), larvae, fry, fry feed and tank water showed that these microorganisms occurred more in advanced fry than in other early stages of fish development. The highest aerobic heterotrophic bacteria and fungi and total coliforms were encountered in fry feed while tank water gave the lowest counts of all microbial groups. A total of 136 bacterial and 13 fungal isolates were identified. The bacteria isolated from the samples were predominantly Gram negative except in fry feed where Gram positive bacteria predominated. Bacteria of the genera Bacillus, Staphylococcus, Micrococcus, Streptococcus, Acinetobacter, Alcaligenes, Flavobacterium, Pseudomonas, Citrobacter, Enterobacter, Escherichia, Klebsiella, Salmonella, Aeromonas, Vibrio and Chromobacterium were isolated from the samples at different frequencies with Staphylococcus, Acinetobacter and Flavobacterium predominating. Fungi of the genera Aspergillus, Mucor, Fusarium, Penicillium, Cladosporium, Phoma, Phialophora, Exophila, Candida, Saccharomyces and Cryptococcus were isolated from the samples with Aspergillus and Saccharomyces predominating and contaminating all the samples. The microbial generic diversity increased with fish development. Key Words: Clarias eggs, larvae, fry, fry feed, hatchery systems, microbial flora Tropical Freshwater Biology 11 (2002) 91-10