Diversity of freshwater fish parasites and water quality of the Kwena Dam, Mpumalanga Province, South Africa

Abstract

The present study was carried out in the Kwena Dam, with the aim of determining selected water quality parameters, parasite diversity and condition factor (K) of Clarias gariepinus (sharptooth catfish), Cyprinus carpio (common carp) and Oreochromis mossambicus (Mozambique tilapia). This study was conducted in autumn (April 2016), winter (July 2016), spring (October 2016) and summer (February 2017). The present study was the first to investigate the parasite composition of these three fish species in the Kwena Dam. A total number of 26 Clarias gariepinus, 21 Cyprinus carpio and 57 O. mossambicus specimens were collected using gill nets of different mesh sizes (30 mm – 120 mm). Each fish was weighed, measured and euthanised by severing the spinal cord. Mucus smears from the skin, fins and gills were examined for ectoparasites using a stereo-microscope. The fish were then dissected and all organs examined for endoparasites. All parasites were fixed and preserved according to standard methods for each parasite group. In situ water parameters were determined using a handheld multi-parameter instrument for each sampling season. In addition, water samples were collected seasonally and sent to an accredited laboratory where they were analysed for selected metals and nutrients. Water quality parameters and the presence of metals in water are of importance in determining the water quality of an aquatic environment. Most water quality parameters were within the Target Water Quality Range (TWQR) for aquatic ecosystems. Aluminium, selenium and zinc had concentrations above the TWQR for aquatic ecosystems. Nutrient concentrations were within the TQWR during all sampling seasons. The water quality did not differ significantly between seasons during the present study. Four parasite groups were reported infecting Cyprinus carpio and these included Monogenea (Dactylogyrus extensus and Dactylogyrus minutus), Digenea (Diplostomum sp.), Cestoda (Atractolytocestus huronensis), Branchiura (Argulus japonicus) and Copepoda (Neoergasilus japonicus). Parasites collected from Clarias gariepinus belonged to four groups, namely Protozoa (Trypanosoma sp.), Monogenea (Quadriacanthus sp. and Gyrodactylus sp.), Nematoda (Paracamallanus cyathopharynx and Contracaecum sp.) and Branchiura (Dolops ranarum). Parasites collected from O. mossambicus belonged to five groups, namely Monogenea (Cichlidogyrus halli, Cichlidogyrus sclerosus, Cichlidogyrus tilapiae and Enterogyrus conoratus), Nematoda (Contracaecum sp.), Cestoda (Neogryporhynchus sp.), Acanthocephala (Acanthogyrus tilapiae) and Branchiura (Dolops ranarum). iv The number of parasite species for the four seasons were as follows: summer (13) > autumn and winter (12) > spring (11). From the Shannon-Wiener index results, O. mossambicus had a higher parasite diversity than Clarias gariepinus and Cyprinus carpio. The Parasite Index (IP) and Inverted Parasite Index (IPI) of the three fish species indicated that the water from the dam is not polluted. The condition factor (K) for all fish species indicated that fish collected from the dam during all sampling seasons were in a good condition and parasite load had little effect on K for all fish species. The use of PI and IPI in conjunction with the fish K can be regarded as a useful tool in freshwater and fish health monitoring. The present results report new geographical records of the parasites of Clarias gariepinus, Cyprinus carpio and Oreochromis mossambicus. Since no parasitological research was done before the present study at the Kwena Dam, the results of the present study form baseline data for future parasitology studies and can consequently be useful in the management and conservation of the Kwena Dam.