Discovery of alien and highly invasive freshwater crayfish in the Free State Goldfields
15 August 2018
The Department of Environmental Affairs (DEA) is working closely with the Free State Department of Economic, Small Business Development, Tourism and Environmental Affairs (FS DESTEA) as well as the local and district municipalities in the Goldfields area to eradicate and stop the spread of red swamp crayfish which was discovered in the Free State. The species is alien and considered to be highly invasive.
Acting on a tip off from a member of the public in Welkom, Dr. Leon Barkhuizen, Aquatic Scientist from the FS DESTEA, discovered a large population of alien and highly invasive red swamp crayfish, Procambarus clarkia, in a dam in the Free State Goldfields. The identification of the species was confirmed by Professor Linda Basson from the Department of Zoology and Entomology at the University of the Free State. The reason for the presence of this alien and highly invasive species in the dam is not clear, but anecdotal reports indicate that it might have been released by members of the public.
During two sampling periods in June 2018, Dr. Barkhuizen caught 53 individuals of which most were juveniles ranging between 2 and 10 cm in length as well as a few adults. From the preliminary results it is clear that it’s an established and breeding population due to the large number of juveniles that were collected. It seems that the crayfish have been present in the area for quite a number of years, considering that two large individuals were found in a swimming pool in the area in October 2017.
Freshwater crayfish do not naturally occur in Africa and a large number of species occur in Europe, America and Australia. The red swamp crayfish, also known as the Louisiana crayfish that was discovered in the Goldfields is indigenous to northern Mexico and south-east United States of America. The species has spread throughout the world, mostly for aquaculture purposes and the pet shop trade.