Abstract
In South Africa freshwater aquaculture is currently dominated by the use of earthen
dams to rear fish for production purposes. Rural fish farmers use river water for their
aquaculture activities. In many areas in the Limpopo Province there are sewage
treatment works that discharge directly into the rivers. A concern exists that this may
pose a threat to the growth of fish. In view of this, a study on water quality
management was done which looked at the effects of an artificial wetland on water
quality and the consequent growth of Oreochromis mossambicus. To determine the
effect of artificial wetlands on water quality, the water quality of the “untreated” water
received at the fish dams was measured and compared with that of “treated” water
that has flowed through an artificial wetland. The study took place between April and
July 2014. The parameters measured were pH, temperature, dissolved oxygen, total
ammonium, nitrite, nitrate and total phosphorous. Chemical variables ranged
between; total phosphorous (0.08-0.33 mg.L-1), nitrate (1.0-3.0 mg.L-1), nitrite (0.04-
0.07 mg.L-1) and ammonium (0.1-0.77 mg.L-1). Results showed that ammonium
concentrations were significantly different (P<0.05) in Dam A as compared to Dam B.
However there was no significant difference (P>0.05) on phosphate, nitrate and
nitrite concentration in both dams. The physical parameters ranged between:
temperature (12.21-27.2 ºC), dissolved oxygen (2.45-9.17 mg.L-1) and pH (5.56-
7.06), but there was no significant difference (P>0.05) in physical parameters
between the two dams. Growth measurements were recorded on commencement of
the study and every two weeks until the end of the experiment. Results showed that
fish growth in weight was slightly higher in a dam that receives “treated” water as
compared to a dam that receives “untreated” water. This study revealed that the
constructed wetland had an impact on water quality, and the improved water quality
had an impact on the growth of fish in Dam A as compared to Dam B.
M.Sc. (Aquatic Health)