Biomarker responses in African sharptooth catfish, Clarias gariepinus (Burchell, 1822), as indicators of potential metal and organic pollution along the Vaal River system, South Africa

The Vaal River is of considerable economic and environmental importance. It flows through five provinces within South Africa and it is subject to numerous recreational and industrial activities, which often prove detrimental to the health of the system. To determine the extent of the impact that these anthropogenic stressors have on the river system, physiological effects in Clarias gariepinus were assessed during a 2016/2017 sample survey using a suite of biomarkers (exposure and effect). Inhibition of acetylcholinesterase and increased metallothionein concentrations were recorded in response to the increase in organic pollutants and metals. Oxidative stress biomarkers, such as superoxide dismutase, showed significant increases in response to possible recent pesticide exposures, whereas lipid peroxidation and protein damage were evident with increased malondialdehyde and protein carbonyl concentrations respectively. The data provide a novel account of the use of biomarkers to assess negative anthropogenic effects observed along the entire length of the Vaal River system.