The Common Carp is a large freshwater fish, growing up to 1m in length and 24 kg in weight. Both colour and scales are variable in this species. It can be found in much of South Africa, and has had a significantly negative impact on the environment. Competition with other organisms for the same food sources has resulted in biodiversity loss.
Rainbow trout are found in cold, well oxygenated water. They are listed under NEMBA as a Category 2 invasive species, meaning that this species is restricted by activity. Rainbow trout have been linked to the decline of some indigenous fish species.
The smallmouth bass is a small predatory fish, reaching up to 60mm in length and 2kg in mass. It is an olive to coppery-yellow colour above, with darker olive vertical stripes and a dusky white underneath. Breeding usually occurs in early summer in shallow waters. Smallmouth bass has caused a decline in indigenous species through environmental degradation and predation.
The grass carp is an herbivorous, freshwater fish species. It was introduced into South Africa from Malaysia and Germany between the years of 1967 and 1975. In large numbers, it can remove all aquatic vegetation from a body of water. If this happens valuable habitat for fish is lost which can cause fish population imbalances.