Crayfish poses threat on aquatic ecosystem of Olifants River
It has come to the attention of nature conservation that freshwater crayfish may be present in a farm dam between Groblersdal and Loskop.
A visit by Mr. André Hoffman, river ecologist at the Mpumalanga Tourism and Parks Agency’s aquatic conservation unit, confirmed this and crayfish of all sizes were found with the largest at 129 grams.
“Urgent measures will now be put into place to limit the crayfish to the dam and a process will begin to eradicate them. A study will also now be done to find out whether the crayfish have spread to the nearby Olifants River and whether there are further populations of the crayfish on other farms in the area,” said Mr. Hoffman.
He appeals to the public for help so that this plague can be eradicated. In South Africa there are no indigenous freshwater crayfish, only shrimps and crabs.
The species of crayfish found, Cherax quadricarinatus, is a declared invasive species native to Australia. It is classified as a category 1b species that needs to be intensively controlled.
It is illegal to own this species and no one is allowed to collect and move it around.
The occurrence of this invader was first found in the Komatie River in 2002 and during a study of the species it was found that it was brought to Swaziland by Adrian Peers from Zambia.
From there they escaped and spread to the Komati River in South Africa.
Populations have now also been found in the Crocodile River and Klipkoppie Dam.
“These crayfish breed very quickly, have few natural predators, spread easily and can spread over land when it rains. In Karibadam, this is already a huge problem in their fishing industry there. They also compete with our native crabs and shrimp and they have a big impact on fish species and other aquatic organisms.”
“No crabs were found in the dam where the crayfish were found locally and it is also very difficult to find fish there. It therefore already indicates the impact of the invader on the aquatic species that should occur naturally,” says Mr. Hoffman.
The public is seriously admonished not to keep or collect or distribute freshwater crayfish.
There is also a serious appeal that anyone who knows where these crayfish occur or sees them should immediately report them to Mr. Hoffman at 082 412 5756.
“Help us to protect our river ecosystems so that we can enjoy our environment for a long time to come.”
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