Abstract
Ph.D.
The current study evaluated a bio-monitoring technique developed in the USA by Adams,
Brown and Goede, 1993. This project was sponsored by the Department of Water Affairs
and Forestry (DWAF), to enable testing of the Health Assessment Index (HAI) under
South African conditions. Testing took place in the Olifants River system, one of the
most polluted river systems . in South Africa. Initially two river points were tested using
Oreochromis mossambicus (Robinson, 1996), Clarias gariepinus (Marx, 1996) and
Labeo rosae (Luus-Powell, 1997). The current study re-tested the HAI at the same two
sample sites, namely Mamba and Balule in the Kruger National Park, using 0.
mossambicus and C. gariepinus respectively. Two additional sites were tested in the
upper catchment area, namely Loskop Dam and Bronkhorstspruit Dam. The current study
further enabled the comparison of HAI results collected during drought and flood
conditions.
Results obtained after deployment of the HAI were corroborated using chemical analysis
of water, sediment and biota. Water and sediment analysis was carried out by the Institute
for Water Quality Studies using standard techniques. Bio-accumulation of aluminium,
copper, iron, lead, manganese, nickel, strontium and zinc was assessed in the gills, liver,
skin and muscle tissue of sample fish using standard Atomic Absorption Spectrometry
techniques. Modifications made to the original HAI involved the inclusion of variable
ranking in the assessment of fish parasites, with endo- and ectoparasites evaluated
separately. Testing of this parasite hypothesis lead to the development of a Parasite Index
component to the HAI.
Assessment of water, sediment and fish tissue determined that the Olifants River system
is indeed exposed to macro and heavy metal pollutants, which negatively affect aquatic
health. Constituents posing the greatest threat are chlorides, fluorides, phosphates, total
dissolved solids, copper and iron concentrations. Testing the HAI and parasite hypothesis
using C. gariepinus, provided the most meaningful results. During testing of the parasite
hypothesis both endo- and ectoparasite numbers conformed to the suggested idea that
higher endoparasite numbers will occur at highly impacted areas, whereby ectoparasite
numbers will be low. This was particularly evident in the lower catchment area, whereby
comparisons between drought and flood conditions were carried out. Subsequent
decreases in water quality directly after the flood were noted using water and sediment
analysis. This observation reflects the results gathered using the HAT and during testing
of the parasite hypothesis at all four sample sites. During statistical analysis of the HAI,
using logistic regression analysis, parasite numbers, more specifically endoparasite
numbers, were the most indicative of fish health. Environmental stressors (flood
conditions) result in immunological responses observed in fish, and are reflected
statistically using the HAI as changes in WBC %. It is suggested that endoparasites and
WBC % provide the best overall assessment of fish condition. These variables should
thus not be eliminated, in order to streamline the HAI evaluation procedures.
Testing of this bio-monitoring technique under South African conditions provided
meaningful results. This indicates that the HAI can be used to assess water quality, with
existing water monitoring programmes further benefiting from its incorporation.