| Summary: | M.Sc. === The Hartbeespoort Dam is located in the North-West Province, downstream of the confluence of the Crocodile River and the Magalies River. The dam was originally built for agricultural purposes and the surrounding area has many canals for irrigation. The use of pesticides for agricultural practices within the area which are transported by the canals, are of great concern. It is well known that residues of persistent pesticides (especially those of organochlorine) and insecticides are found in terrestrial and aquatic environments as well as in the organisms occupying these niches. Such xenobiotics are highly lipid soluble and lengthy exposure to them results in their high accumulation in non-target organisms, all contributing to adverse effects on the ecosystem. The upper Olifants River catchment comprises the drainage areas of the Olifants River, Klein Olifants River and Wilge River, with tributaries down to the Loskop Dam. Over the past few years, the Olifants River has been systematically impaired because of an increase in agricultural and mining activities, industrial development and urbanisation. Recent fish kills in the Loskop Dam has lead to many controversies about the water quality in the Olifants River. The aim of this study was to determine through the use of biomarker responses if it would be possible to identify whether sub-lethal pesticide exposure occurs in fish populations in the Crocodile- and Olifants River systems. Both active biomonitoring (ABM) and passive biomonitoring (PBM) were carried out at selected sites in the Crocodile River system. The ABM technique involved the transplantation of bioindicator organisms, in this case fish, and exposing them for a period of four weeks. The ABM and PBM exposures were carried out during different pesticide spraying regimes, which also coincided with high (summer) and low (winter) flow conditions. Following the exposure period, the organisms were removed and assessed for biological responses (biomarkers). General biomarker responses used in pesticide exposure i.e. acetylcholinesterase (AChE), malondialdehyde (MDA), catalase activity (CAT), protein carbonyls (PC), cellular energy allocation (CEA) and condition factor (CF) were determined. The same suite of biomarkers used in the Crocodile River system was used to determine responses in resident fish species in the Olifants River system.
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