Abstract
M.Sc. (Zoology)
The necessity to maintain high water quality standards has become essential not only to man, but also to conserve aquatic life forms. The Olifants, Selati and Letaba Rivers were monitored for water quality
variables and metal concentration in water, sediments and muscle, gill, fat, gonads, liver, bile, blood
and kidney of the sharp tooth catfish, C. qariepinus. Some of the water quality variables measured
were not within the limits of those standards set for the protection of fish and other aquatic life forms.
Turbidity seems to be the biggest problem, due to the Phalaborwa barrage. Metal concentrations
were found, in descending order, highest in the sediment, fish and water. This pose the problem of
metals being reintroduced into the water column when physico-chemical conditions are not favourable.
Experimental studies were done with copper on adult C. qariepinus, due to the extensive copper
mining activities in the Phalaborwa region. Haematological and enzymatic analyses revealed a
interference in metabolic activity after 96 hour copper exposure. Histological studies on the gill morphology, showed an alteration in the structure with a resultant change in respiratory and osmoregulatory function. LC-50 values were determined for adult and juvenile C. qariepinus in order to set new standards for the protection of aquatic lite in a rapidly developing South Africa.