Freshwater crayfish invasions in South Africa

Freshwater crayfish invasions in South Africa
Ana L. NUNES1, 2, 3, Tsungai A. Zengeya4, G. John Measey1, Olaf L.F. Weyl2
1Centre for Invasion Biology, Department of Botany and Zoology, Stellenbosch University
2Centre for Invasion Biology, South African Institute for Aquatic Biodiversity, Grahamstown
3Invasive Species Programme, South African National Biodiversity Institute, Kirstenbosch Research Centre
4South African National Biodiversity Institute, Pretoria National Botanical Gardens

No indigenous freshwater crayfish species exist in continental Africa, but several North American and Australian species have been introduced since the 1970s. In South Africa, four species of alien crayfish are listed under NEMBA’s National List of Invasive Freshwater Invertebrate Species: the Danube crayfish (Astacus leptodactylus), the common yabby (Cherax destructor), the Australian redclaw crayfish (Cherax quadricarinatus) and the marron (Cherax tenuimanus). Although freshwater crayfish have been reported as high-impact invaders that can cause serious negative environmental impacts, no detailed information exists on crayfish distribution, abundance and impacts in South Africa.

The aim of this study is to present an overall view of the current situation of crayfish invasions in South Africa, mostly by focusing on the Australian redclaw crayfish (C. quadricarinatus), the only species that appears to be present and widely distributed in some areas of South Africa. Here we show the results of initial crayfish surveys performed in South Africa and Swaziland, for which collapsible baited traps were set along water bodies, left overnight, and checked the following morning for crayfish presence. We report on the presence of established populations of C. quadricarinatus in Mpumalanga and in different areas of Swaziland.

We discuss the implications of these results regarding the potential impact of C. quadricarinatus on native biota and natural habitats. This information is essential to support the development and implementation of adequate action plans for the management and control of this invasive species in South Africa.