Bioaccumulation of Bacterial Indicators of Faecal Contamination in African Catfish (Clarias gariepinus) Raised in a Concrete Pond
This study was carried out to determine the rate of bioaccumulation of bacterial indicators of faecal contamination in African catfish (Clarias gariepinus) in a concrete pond in Akure, Nigeria. Clarias gariepinus and samples of their growing waters were collected weekly over a period of twelve weeks. The concentration of Escherichia coli, faecal coliforms, intestinal enterococci, Salmonella and Shigella were determined by standard microbiological method. The accumulation factor of each parameter was determined by dividing the log concentration of each microorganism in C. gariepinus by the corresponding log concentration in their growing waters. Physicochemical properties of the growing waters were determined using standard methods. The accumulation factor of E. coli ranged from 0.93 to 1.03; faecal coliforms 0.94 to 1.02 and intestinal enterococci 0.91 to 1.01. Positive correlations were observed between water temperature and the bioaccumulation of faecal coliforms (r = 0.71) in C. gariepinus. The findings of this study suggest that the rate of bioaccumulation of faecal indicator bacteria in C. gariepinus to a large extent depends on the physicochemical characteristics of the growing waters. Hence, fish raised in faecally impacted waters must be adequately cooked before consumption in order to prevent the occurrence of foodborne illness.
Keywords: Accumulation factor, foodborne illness, microorganism, physicochemical characteristics, surface water