Bioaccumulation of copper and zinc in Oreochromis mossambicus and Clarias gariepinus, from the Olifants River, Mpumalanga, South Africa

The upper and lower catchments of the Olifants River, South Africa, are subject to numerous anthropogenic influences that adversely affect water quality, including zinc (Zn) and cadmium (Cd) levels. Monitoring of Cd and Zn in tilapia and catfish from the river has indicated elevated concentrations. Copper content in organs and tissues are reported; no similar patterns were observed for Zn. Bioaccumulation differed in the two species, possibly because of different behavior and feeding habits. Greater bioaccumulation was detected during high flow periods, possibly because of sediment-bound metals coming into contact with fish at higher intensities. More holistic biomonitoring is needed in the river to assist managers in reducing metal accumulation.