In the Kruger National Park (KNP), pansteatitis in sharptooth catfish, Clarias gariepinus (Burchell), was shown to be a serious problem in the inlets to large man-made lakes fed by rivers arising in the polluted catchments of the Olifants and Sabie rivers. An increasing prevalence of pansteatitis was recorded in catfish from the Olifants River gorge. A low prevalence was found in catfish upstream of the gorge at two further sites. No pansteatitis was detected in catfish from a rain-filled dam distant from the potential pollution sources affecting the Olifants River and in rivers arising outside of the park that were not dammed. Analysis of stomach content indicated a higher prevalence of fish in the diet of catfish affected by pansteatitis than in those not affected. Significant pathology in catfish was limited to changes associated with a generalised necrosis and inflammation of adipose tissues (pansteatitis), and there was evidence that lesions accumulated over time. Similar pathology was found in a captive population of catfish with known nutritional pansteatitis. Pathology in other organs that might have been attributed to pollution could not be demonstrated. Examination of blood smears and measurement of haematocrit, blood haemoglobin, serum vitamin E and erythrocyte glutathione peroxidase values did not prove useful as monitoring tools, probably because of the episodic exposure to oxidative stress and the chronic nature of the condition. Pansteatitis-affected catfish, kept in an experimental pond for 11 months after the inciting nutritional cause had been removed, retained steatitis lesions almost unaltered. Whereas lipolysis appeared to be reduced by pansteatitis, adipogenesis appeared to be unaffected. Juvenile catfish confined in experimental tanks with sediments from sites where pansteatitis occurred remained healthy, and no pathology developed after 14 months, suggesting that sediments were not directly toxic. The results of the study present the first record of pansteatitis in both wild and farmed African sharptooth catfish and emphasize the ecological importance and complexity of nutritional oxidative stress in a disturbed aquatic environment. Nutrient entrapment and the consumption of phytoplankton-feeding fish rich in polyunsaturated fats, particularly silver carp, Hypophthalmichthys molitrix (Valenciennes), a species alien to Africa but present in the Olifants River, is proposed as the dietary cause of the pansteatitis. / Thesis (PhD)--University of Pretoria, 2012. / Paraclinical Sciences / unrestricted

Since 2008, large numbers of Nile crocodile (Crocodylus niloticus) carcasses were found in the Kruger National Park (KNP), South Africa. Most of the crocodile carcasses were found in the Olifants Gorge, which is situated below the Letaba and Olifants river confluence, before the Mozambique border and Massingir Dam. The Massingir Dam is an important resource and it plays a significant role in the welfare of the local Mozambican population. Autopsies performed on the crocodiles indicated that the adipose tissue colour changed from normal white to yellow and this is usually a sign of pansteatitis. Pansteatitis is caused by lipid peroxidation in an organism and it is characterised by the lack of vitamin E. This disease is recognisable by the hardening of the fatty tissue and yellow discolouration, and is mostly associated with aquatic organisms from polluted ecosystems. There are speculations that the crocodile fatalities may be associated with the Massingir Dam that backed up into the Olifants Gorge after flooding. After the dam was reconstructed, it flooded the Olifants Gorge, causing it to act like a localised sediment trap as the water flow slowed down and as a result, caused pollutants to build-up. Sediment samples were collected from selected rivers and ponds within the KNP. These samples were analysed for selected elements, persistent organic pollutants (POPs), and polycyclic aromatic hydrocarbons (PAHs). The sediment samples were analysed in Norway for POPs and PAHs with the use of a high-resolution gas chromatography/mass spectrometry (GC/MS) and the heavy metals were analysed in South Africa with the use of inductively-coupled plasma mass spectrometry (ICP/MS). In order to identify which elements may have affected the health of the crocodiles, a series of sediment quality indices were used. These indices made it possible to determine which elements may have been involved. The order of probability of heavy metals causing harm was Se>As>Ni>Cr>Cu>I>V>Mn>Co>Fe>Cd>Hg>Zn>Pb>Ba>U. The data was compared to selected international guidelines. All the information was used to determine which of the sampled sites had the highest contamination. The sites sampled with the highest concentrations were in the Crocodile, Nkomati, Olifants, and Letaba Rivers. Concentrations of the elements, POPs, and PAHs were also quantifiable in the Olifants Gorge. The following elements (Fe, Co, Cu, Cr, Pb, V, As, and Ni) were quantified at elevated levels and may therefore have caused negative effects on the crocodiles in the Olifants Gorge. These elevated concentrations, in combination with the dramatic change in the physical environment due to the dam, could have added additional stress that may have contributed to the observed crocodile mortalities in the Olifants Gorge. / MSc (Environmental Sciences), North-West University, Potchefstroom Campus, 2015

Since 2008, large numbers of Nile crocodile (Crocodylus niloticus) carcasses were found in the Kruger National Park (KNP), South Africa. Most of the crocodile carcasses were found in the Olifants Gorge, which is situated below the Letaba and Olifants river confluence, before the Mozambique border and Massingir Dam. The Massingir Dam is an important resource and it plays a significant role in the welfare of the local Mozambican population. Autopsies performed on the crocodiles indicated that the adipose tissue colour changed from normal white to yellow and this is usually a sign of pansteatitis. Pansteatitis is caused by lipid peroxidation in an organism and it is characterised by the lack of vitamin E. This disease is recognisable by the hardening of the fatty tissue and yellow discolouration, and is mostly associated with aquatic organisms from polluted ecosystems. There are speculations that the crocodile fatalities may be associated with the Massingir Dam that backed up into the Olifants Gorge after flooding. After the dam was reconstructed, it flooded the Olifants Gorge, causing it to act like a localised sediment trap as the water flow slowed down and as a result, caused pollutants to build-up. Sediment samples were collected from selected rivers and ponds within the KNP. These samples were analysed for selected elements, persistent organic pollutants (POPs), and polycyclic aromatic hydrocarbons (PAHs). The sediment samples were analysed in Norway for POPs and PAHs with the use of a high-resolution gas chromatography/mass spectrometry (GC/MS) and the heavy metals were analysed in South Africa with the use of inductively-coupled plasma mass spectrometry (ICP/MS). In order to identify which elements may have affected the health of the crocodiles, a series of sediment quality indices were used. These indices made it possible to determine which elements may have been involved. The order of probability of heavy metals causing harm was Se>As>Ni>Cr>Cu>I>V>Mn>Co>Fe>Cd>Hg>Zn>Pb>Ba>U. The data was compared to selected international guidelines. All the information was used to determine which of the sampled sites had the highest contamination. The sites sampled with the highest concentrations were in the Crocodile, Nkomati, Olifants, and Letaba Rivers. Concentrations of the elements, POPs, and PAHs were also quantifiable in the Olifants Gorge. The following elements (Fe, Co, Cu, Cr, Pb, V, As, and Ni) were quantified at elevated levels and may therefore have caused negative effects on the crocodiles in the Olifants Gorge. These elevated concentrations, in combination with the dramatic change in the physical environment due to the dam, could have added additional stress that may have contributed to the observed crocodile mortalities in the Olifants Gorge. / MSc (Environmental Sciences), North-West University, Potchefstroom Campus, 2015