Abstract
M.Sc. (Environmental Management)
The Kruger National Park (KNP) is a world renowned wildlife reserve and a source of South African ecotourism benefiting the economy. The Olifants River is the largest river running through the KNP and it is known to be one of South Africa’s most polluted rivers. In the winters of 2008 and 2009 Nile crocodile carcasses were found in the Olifants River gorge in the KNP. In a very short period nearly the entire population of Nile crocodile was lost, the cause of which was later identified as pansteatitis. Pansteatitis is caused by lipid peroxidation known to be nutritionally mediated, as it is associated with diets high in polyunsaturated fats, often of fish origin and insufficient antioxidants specifically vitamin E, which is solely synthesized by plants and must therefore be obtained through diet. The hypothesis of this study is therefore that the fish inhabiting the Olifants River are antioxidant deficient, more specifically, vitamin E deficient, causing the wildlife e.g. crocodiles and predatory fish species, that feed on the fish, to become vitamin E deficient as well, and subsequently develop pansteatitis. If the hypothesis is true, the top fish predator in this aquatic system, the tigerfish Hydrocynus vittatus, should therefore also exhibit signs of dietary vitamin E deficiency. The aim of this study was to determine if tigerfish from the Olifants River in the KNP are exhibiting any signs of antioxidant deficiency, specifically vitamin E deficiency. The objectives to accomplish this aim were firstly to analyse the total plasma antioxidant activity using an ELISA assay, and secondly, to perform a histology-based fish health assessment on the target organs of the tigerfish to identify any histological alterations, specifically those known to be associated with vitamin E deficiency. The results were compared to the results from fish of the same species from two reference sites where there have been no signs of vitamin E deficiency, such as pansteatitis-related wildlife deaths. The results of the plasma analysis as well as the histological assessment showed no conclusive signs of vitamin E deficiency in tigerfish from the Olifants River. It is therefore unlikely that the pansteatitis in the affected wildlife is caused by dietary vitamin E deficiency in the aquatic system, but rather by vitamin E depleting mechanisms such as the presence of high amounts of toxicants with pro-oxidant properties, which may be causing an imbalance of pro-oxidants and antioxidants within the body. Hence the rate of vitamin E regeneration cannot keep up with the rate of oxidation. This is occurring only in certain species due to their specific behaviour or eating habits.