Bacterial load, composition and succession in the African catfish, Clarias gariepinus (Burchell, 1822) held at ambient temperatures.

Microorganisms, especially bacteria are the major causes of spoilage in fresh fish. In the coastal areas of developing tropical countries where ambient temperatures are usually high and access to modern preservation and processing technologies is low, fish is often left under ambient conditions for long periods after capture, resulting in quality deterioration and spoilage with attendant increases in post harvest losses. This study was carried out to identify, characterize and estimate the number of colony forming units (CFU) of microorganisms associated with freshly slaughtered African catfish, Clarias gariepinus held at ambient temperatures. Microorganisms were isolated from the flesh, gills, guts, mouth and skin of fish samples at successive 6-hour intervals post-slaughter for 42 hours when the fish were adjudged spoilt by a 5-member trained assessment panel. Determination of viable bacterial count was carried out by introducing aliquots of three dilutions of samples into nutrient agar plates, incubating at 37oC for 24hrs and counting the number of CFU. Microorganisms were thereafter identified using colonial and morphological characteristics and biochemical tests. Organoleptic assessment of fish samples were carried out by a 5-man trained panel. Results showed that a total of eleven microorganisms of pathogenic and/or spoilage importance were isolated at various intervals from fish samples, including Acinetobacter spp, Bacillus subtilis, B. megaterium, Citrobacter freundii, Enterobacter cloacae, Escherichia coli, Klebsiella oxytoca, K. pneumoniae, Proteus mirabilis, Pseudomonas lundensis and Staphylococcus aureus. Generally the number of CFU from various parts of fish increased significantly (P < 0.05) as time interval increased.