Abstract
Roodeplaat Dam is classified as a hyper-eutrophic ecosystem due to the high
nutrient enrichment (nitrogen and phosphorus) which results in the production of
cyanobacteria. The cyanobacteria produce toxins, e.g. microcystin (a known
hepatotoxin), which have been reported to affect fish health negatively. Sharptooth
catfish Clarias gariepinus inhabiting this system has been reported to exhibit
macroscopically-visible hepatic nodular alterations. Although the exact cause of
these nodules has not yet been confirmed, it has been hypothesized that exposure
to microcystins might play a role. Recent, unpublished findings have shown high
levels of microcystins in the liver tissue of C. gariepinus from Roodeplaat Dam.
Previous reports provided information on the general histology of the nodular livers...
M.Sc. (Aquatic Health)