Health of sharptooth catfish Clarias gariepinus in Pongolapoort Dam, South Africa: a comprehensive study

A histology-based fish health assessment protocol was used in 2009-2010 to assess the health status of Clarias gariepinus from Pongolapoort Dam, South Africa. Nineteen fish were collected by angling. The histology of liver, kidney, gills and testes or ovaries was semi-quantitatively assessed and compared to that of fish from a reference site in the Okavango Panhandle, Botswana. Necropsy observations indicated that C. gariepinus from Pongolapoort Dam were in poorer condition than those from the Okavango Panhandle. Microscopic analysis showed that the mean liver index (I-L), gill index (I-G), testis index (I-T) and ovary index (I-O) were higher, although not statistically significant, in fish from the Okavango Panhandle. The difference in the results between the necropsy-based observations and semi-quantitative histological results was due to the external abnormalities detected in the necropsy analysis, including parasites and skin lesions, not expressing as changes to cell and tissue structure. According to the parameters measured, C. gariepinus from Pongolapoort Dam were in a healthy state.