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Triploid grass carp
Common name:Triploid grass carp
Scientific name:Ctenopharyngodon idella
Alternative common names:
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.
Where does this species come from?Eastern Asia from the Amur River in Russia to the West River in southern China.
What is its invasive status in South Africa?Triploid grass carp is not listed for dams within discreet catchments systems in which it occurs. NEMBA category 2 for release of triploid grass carp into dams in discrete catchments systems in which it does not occur. NEMBA category 2 for release of triploid grass carp into rivers, wetlands, natural lakes and estuaries in which it occurs. NEMBA category 3 in all rivers, wetlands, natural lakes and estuaries in which it occurs.
Where in South Africa is it a problem?It was introduced into dams in KwaZulu Natal and the Mpumalanga provinces of South Africa and obviously there have been quite a few escapes and re-introductions as they are very well represented in many freshwater systems all over the country especially in the Vaal River.
How does it spread?It was originally introduced into the country into farm dams to control the weed population.
Why is it a problem?They are known to completely eliminate aquatic plants in introduced habitats altering trophic structure and inflicting widespread detrimental effects on ecosystems, They compete with native invertebrates and fish for food and other important resource and also carry diseases and parasites which are transmittable to other fish and are believed to be the main vector for Asian tapeworms
What does it look like?Description: The body is rhombus with moderately large scales, while the head has no scales. There are three simple and seven branched rays on the dorsal fin. Grass carp are silvery to olive in colour, lacking the golden hue of common carp, and they have no barbells. This species typically reaches sizes of 30 to 36 kg’s in its native habitat, but individuals approaching 181 kg’s have been reported. Habitat: Includes large, slow moving or still water. Although they are often found in shallow streams and fast flowing rivers. They are very tolerant of temperature change and can withstand anything from 0-38 degrees! Breeding: They have a high reproductive potential some individuals sexually mature as early as 6 months of age. Litter size averages 6 piglets, but ranges from 3-8 piglets. Females can give birth twice in one year.