A comparative assessment of the health status of feral populations ofClarias gariepinusfrom three dams in the Limpopo and Olifants river systems, Limpopo province, South Africa, using the fish health assessment index protocol

Abstract

An evaluation of the health status of feral populations of the freshwater catfish Clarias gariepinus was carried out between 2009 and 2010 at three dams in the Limpopo and Olifants river systems with varying levels of human impact. Fish health was assessed using a modified health assessment index (HAI) protocol, with the inclusion of the inverted parasite index (IPI) and condition factor (K). These biomonitoring tools provide relatively simple and rapid indications of how well fish are coping in their environment. To verify the biomonitoring results, water quality analyses were included in the study. The nutrients and mining-related pollutants in the three dams differed to a great extent and showed an increasing trend in the order: Luphephe-Nwanedi Dams < Flag Boshielo Dam < Return Water Dam. The HAI score varied across the three sampling sites, with individual mean values of 93.3, 84 and 42.7 at the Return Water Dam, Flag Boshielo Dam and Luphephe-Nwanedi Dams, respectively. The top six metrics that correlated best with fish health scores were the levels of ectoparasites, haematocrit values and the condition of the gills, liver, skin and fins. Although the HAI successfully differentiated among the three localities, which differed in water quality, it was non-specific in response to contaminants. Notably, the premise set forth by the IPI that endoparasites increase with a decrease in water quality was not supported.

Metal contamination and human health risk associated with the consumption ofLabeo rosaefrom the Olifants River system, South Africa

“…The concentrations of aluminium, lead and iron in surface waters were comparable to those of previous studies (Madanire-Moyo et al 2012;Oberholster et al 2012). Aluminium, copper and lead were above the target water quality range (TWQR) at both impoundments.…”

A histological evaluation of pansteatitis‐affected Mozambique tilapia, Oreochromis mossambicus (Peters 1852), from different geographical locations in South Africa

“…For example, lamellar telangiectasia (aneurysms) reported for one specimen from Lake Loskop can be attributed to the influx of metal pollutants, as the mechanism of dissolved metals toxicity is reported by Madanire‐Moyo et al. (2012a) to interfere with osmotic balance and respiratory processes that result in the coagulation of mucous on the gills. Alternatively, it could be a result of increased pressure within the lamellar capillaries caused from the netting and retrieval process when catching fish.…”

“…Lake Flag Boshielo (S 24°46′59.99″: E 029°25′23.99″) was constructed in 1987, and in 2005, the dam was raised by a further 5 m to a height of 30 m (Ashton, 2010). The reservoir is situated about 85 km downstream of Loskop Dam and approximately 25 km north‐east from the town of Marble Hall (Madanire‐Moyo, Luus‐Powell, & Olivier, 2012a, 2012b), which is situated in the southern and middle region of the Limpopo Province. With a catchment area of 4,213 km 2 , a mean depth of 8.15 m (Dabrowski, Oberholster, & Dabrowski, 2014) and a surface area of 1,288 ha, the storage capacity of the lake is 185.1 million m 3 .…”

“…The lake forms part of the Limpopo River Basin. Constructed in 1964 for irrigation purposes, the impoundment is comprised of twin lakes that are connected by a 2.5 m deep channel (Madanire‐Moyo, Luus‐Powell, & Olivier, 2012a, 2012b). Combined, the lakes have a surface area of 198.2 ha and a storage capacity of 20.11 million m 3 .…”

“…Due to the lack of medium‐ to large‐scale industrial, mining and agricultural activities within the watershed of the lakes, aquatic conditions are considered by Oberholster, Ashton and Macmillan (2009) and Madanire‐Moyo et al. (2012a), Madanire‐Moyo et al. (2012b) to be relatively unpolluted and, for the purpose of this study, were used as a reference site.…”