Steatitis in wild sharptooth catfish, Clarias gariepinus (Burchell), in the Olifants and Lower Letaba Rivers in the Kruger National Park, South Africa

Abstract

Large numbers of adult Nile crocodiles

Impact of temporary desiccation on the mobility of nutrients and metals from sediments of Loskop Reservoir, Olifants River

“…Despite significant efforts to determine the cause of pansteatitis at both locations, the ultimate cause remains elusive. Potential causes that have been explored include opportunistic piscivory following fish kills (Dabrowski et al, 2014a); bioaccumulation of Al and Fe in the food chain (Oberholster et al, 2012); and altered aquatic food-webs (Huchzermeyer et al, 2011). Outbreaks of pansteatitis in aquatic fauna concurrent to blooms of M. aeruginosa have been previously documented (Nichols et al, 1986;Neagari et al, 2011); however, no definitive link between the disease and cyanobacteria has been established.…”

Chemical characteristics and limnology of Loskop Dam on the Olifants River (South Africa), in light of recent fish and crocodile mortalities

“…Since then the population has been in decline (Ferreira and Pienaar, 2011). The condition has also been reported in sharptooth catfish (Clarius gariepinus) at the same location (Huchzermeyer et al, 2011). The occurrence of the disease in two geographically distinct fish and crocodile populations on the same river is peculiar, especially as there have been no reports of the disease occurring between these locations.…”

“…The only other incidence of pansteatitis in wild animal populations in South Africa was reported further downstream, in the Olifants River gorge in the Kruger National Park, where over 180 crocodiles died and were diagnosed with the condition (Huchzermeyer et al, 2011). Since then the population has been in decline (Ferreira and Pienaar, 2011).…”

Chlorinated, brominated, and fluorinated organic pollutants in Nile crocodile eggs from the Kruger National Park, South Africa

“…Of the 37 dead crocodiles that were inspected, 83 per cent were males. Steatitis was also detected in fish, terrapins, and herons at different locations on the Olifants River (Myburgh and Botha, 2009;Ashton, 2010;Huchzermeyer et al, 2011). Parasitic and bacterial diseases have been excluded.…”

“…Parasitic and bacterial diseases have been excluded. The exact cause(s) of the steatitis is not yet known, but speculation includes microcystins from cyanobacteria in the water and food of the crocodiles (Myburgh and Botha, 2009), trapping of pollutants settling out of the water due to the effect of the river slowing down in the upper reaches of the Massingr Dam across the border in Mozambique (Osthoff et al, 2010), crocodiles feeding on dead and rancid fish caused by anthropogenic ecosystem impacts (Ashton, 2010), crocodiles feeding on dead and rancid fish from fishnets (Huchzermeyer et al, 2011), broad-scale cascades of environmental deterioration and pollution (Ferreira and Pienaar, 2011), crocodiles feeding on local catfish (Clarias garipienus) with steatitis with no known cause but pollution is suspected (Huchzermeyer et al, 2011), changes in the food web due to changes in the ecosystem, combined with a yet to be found extralimital fish species as vector of the cause (Woodborne et al, 2012), high concentrations of aluminium in the body fat of Nile tilapia (Oreochromus mossambicus) that interferes with cellular metabolism (including lipid-peroxidation) and affects predators such as crocodiles (Oberholster et al, 2012), a seasonal dietary change due to upstream migration of alien silver carp (Hypophthalmichthys molitrix) with a fatty acid composition different from local fish (Huchzermeyer, 2012).…”