Aquaculture can be defined as the practice of raising aquatic organisms for food or other commercial uses. The health and development of aquatic organisms in aquaculture systems are significantly influenced by the quality of the water. The farmed species may experience stress, disease outbreaks, or even death as a result of poor water quality. Therefore, common water quality issues need to be addressed to ensure optimal conditions for their aquatic species. This study focused on the assessment of water quality issues in aquaculture at Vaal River system in Gauteng, South Africa to ensure optimal conditions for aquatic species.
In this study, the main stream of the Vaal River system was sampled. Most analytical methods used in this study follow the standard methods for examination. The following fundamental physico-chemical and biological parameters were assessed according to the standard methods for the examination of water: ammonia, total alkalinity, dissolved oxygen, sulphate, chloride, conductivity, total dissolved solids (TDS), phosphate, pH, temperature, E-coli, and algal pigments. These parameters were chosen because the constitute the common parameters in water quality analysis that should be frequently monitored to ensure optimal conditions for aquatic species.
The results showed the high TDS concentration (~177 mg/L) in the main stream of the Vaal river system is a potential threat to the agricultural sector, as it could be impacting on crop and aquacultural production. Oxygen concentrations are not regularly measured in the Vaal River, however, indications are the concentrations are usually relatively high (>60%). The concentrations of metals in the Vaal River is generally high, leading to frequent fish kills. Furthermore, the high TDS concentrations in the Vaal River evidently influence the turbidity of the water. And the higher pH values (6.3-8.7) in the Vaal River can be ascribed to higher algal concentrations. The high concentrations in E-coli (240 counts/100 ml) and algal pigments (69 mg/L) constitute a high risk the aquaculture production in the Vaal River system. A range of water related problems are currently being experienced by water users in the Vaal River system due to the current water quality status that prevails.
For the purposes of this study, the water quality issue needs to be assessed and addressed by re-evaluating new management options and/or application of treatment technology. The results would be helpful for the relevant authorities to select water quality monitoring parameters in the aquaculture areas.