Abstract
M.Sc.
The Olifants- and Luvuvhu rivers both flow through the Kruger National Park (KNP). The Olifants River (OR) is a major tributary of the Limpopo River with water quality being less than desirable due to high concentrations of pollutants as a result of the activities in the upper catchment. The crocodile population of the river declined from 1000 in 2008 to 347 in 2009 due to pansteatitis. Labeobarbus marequensis in the upper catchment also showed symptoms of the disease (Templehoff, 2010). This raised concern about the health of the fish in the OR, particularly in the section flowing through the KNP. The Luvuvhu River (LR) is also a tributary of the Limpopo River with main land uses in the catchment being agriculture, mining and communal lands. Of concern is the finding of DDT residues in water, sediment, and domestic and indigenous biota upstream of the sites sampled in this study (Barnhoorn et al., 2009) which raised concerns about the health of fish in the lower reaches of the river flowing through the KNP. Therefore, the aim of this study was to assess the health status of
[9]
selected fish species from the OR and LR in the KNP using a histology-based health assessment protocol (HBHA). The species selected for this study included Hydrocynus vittatus, Labeobarbus marequensis, Labeo cylindricus and Labeo rosae. The OR was sampled in September 2009 and May 2010 while the LR was sampled in November 2009 and April 2010. A necropsy was done to determine if there were any internal or external macroscopic alterations with any alterations noted on a score sheet. Blood was taken for haematocrit (Hct), leukocrit (Lct) and total plasma protein (TP) determination. As part of the HBHA, a necropsy-based health assessment index (HAI) was applied using a modified protocol of Adams et al. (1993) where the necropsy and blood parameters were used to calculate the mean and sum HAI for the different species sampled on each sampling trip. Biometric indices including the condition factor, hepatosomatic index, splenosomatic index and the gonadosomatic index were calculated. Age was determined using otoliths for tigerfish and scales for the other species. Samples of selected organs (liver, kidney, gill, testes or ovaries) were taken for histological analysis. Microscope slides were assessed qualitatively to identify any histological alterations present. These results were semi-quantitatively assessed according to the protocol of Van Dyk et al. (2009a) from which an organ index and fish index were calculated. The organ index is an indication of the number and severity of histological alterations in a particular organ of a selected species. The organ indices were classed according to the classes of Van Dyk et al. (2009a) with Class 1 (<10) being tissue with slight histological alterations; Class 2 (10-25) being tissue with moderate histological alterations. The fish index is a sum of all of the organ indices for any given fish sampled.