City of Tshwane officials say indigenous fish at the Rietvlei Dam are under pressure from exotic species.
The city started a research and survey project at the dam, which will later be extended to all five municipal dams.
MMC for the Environment, Dana Wannenburg, says netting at Rietvlei Dam indicated low numbers of indigenous species. He adds that bass are predatory fish, and their proliferation has a detrimental effect on indigenous species, such as kurper and yellow fish.
Wannenburg says while carp are not predatory, they have a significant impact on the ecosystem by out-competing indigenous fish for food. He says they will eventually remove exotics and replace them with local species.
“The natural fish that you will find in a dam like this will be your indigenous fish, like your yellow fish. We have to have that balance in the end that you have more indigenous fish than the exotic predatory fish that you have on the other side. So we must look at the balance between the different fish in the dam itself.
When we did the netting we found more exotic baby fish so it already shows that predatory fish is eating more of the indigenous fish in the end so that balance must be corrected,” explains Wannenburg.
