Baseline metal levels in Clarias gariepinus & Crocodylus niloticus in the Kruger National Park in relation to pansteatitis – preliminary findings Roger Dixon, David Huchzermeyer, Herman Espach & Fritz Huchzermeyer.
Reason The death in the Olifants River Gorge between 2008 and 2010 of crocodiles • suffering from steatitis has resulted in a coordinated, multidisciplinary approach by various investigators and organisations to find the cause or causes. Many different vectors have been postulated as the cause of the steatitis, • observed not only in the crocodiles, but also in the barbel, a major food source for the crocodiles. Included amongst these are toxicological causes which could be ascribed to the • cumulative effects certain groups of chemicals, such as pesticides from agricultural use, and heavy metal accumulation from mining activities. A number of studies have been launched to determine which are the causative • factors. This study addresses the potential problem of heavy metals, considering the presence of active mines upstream.
Sampling As part of the ongoing investigation, many tissue samples have • been collected from Clarias gariepinus from a number of localities within the Kruger National Park, including the highly polluted traversing rivers. For comparative purposes samples were collected from an • unpolluted dam fed entirely from streams arising within the park. Further comparative samples were collected from farmed • specimens at a locality outside the Park. Similarly, tissue samples have been collected from Crocodylus • niloticus.
Sampling in the Olifants Gorge
Clarias gariepinus
Results • Wet liver samples of Clarias gariepinus were digested in nitric acid, and analysed by ICP-MS for 65 elements • The elements shown are those detected, and an average value is presented for three sites: – Olifants Gorge – damned river, natural? diet, pansteatitis – Reenvoel Dam – earth dam, natural diet, healthy fish – Lunsklip fish farm – earth dam, unnatural diet (fish slaughterhouse waste), severe pansteatitis
Relative abundance of major elements in Clarias gariepinus Ca K Reenvoel Dam Fe Olifants Gorge Lunsklip Mg Na 0 2000 4000 6000 8000 10000 12000 14000
Relative abundances of trace elements in Clarias gariepinus Al Pb Hg Ag Reenvoel Dam Mo Olifants Gorge Lunsklip Se Zn Cu Ti 0 10 20 30 40 50 60
Conclusions so far… The high Fe level in the livers of the Lunsklip fish is very different • from those in the Olifants and Reenvoel fish – reflective of different initiating causes of pansteatitis Ag & Hg are attributed to mining activities - a possible trigger • initiating redox cycling and lipid peroxidation (Kelly et al. 1998). Cu & Zn are correlated with local geology • Al, Mo & Se are attributed to the food source • Pb & Ti are anthropogenic •
Still to do... • Analysis of barbel samples from other rivers • Analysis of crocodile samples from across Kruger • Comparison of barbel metal levels on western and eastern borders • Determine whether the metal contents in the fish have a similar distribution in the crocodiles
Recommend
More recommend
