Rapid Establishment and Impact Assessment of the Redclaw Crayfish (Cherax quadricarinatus) Invasion in the Kruger National Park, South Africa

Amidst the rapid degradation of the environment, protected areas act as a buffer for sensitive species against drivers of change. The Kruger National Park, in the Zambezian Lowveld Freshwater Ecoregion, encompasses two critical transboundary river basins, which are threatened by overexploitation, climate change and nonnative invasive species. We complete an assessment of the abundance, distribution, spread and potential impacts of the invasive redclaw crayfish on community assemblages throughout the five main rivers of the Kruger National Park and compare them to other invasive populations in Southern Africa. Redclaw crayfish have established populations in the Crocodile River and the Sabie-Sand River and are spreading at a rate of 7–8 km/year downstream and 3 km/year upstream. Abundance is lower than the more established invasions, but based on other trajectories, we can expect a tenfold increase in the next 5 years. No impact of crayfish presence or abundance was detected on fish or macroinvertebrate community assemblages. This suggests that as crayfish abundance is still relatively low, there may be a window of opportunity for targeted management. Management options in the rivers of the Kruger National Park are fraught with practical issues due to dangerous megafauna, but further understanding of the role of environmental flows on the establishment capacity of redclaw crayfish may hold some potential. Preventing new incursions into the protected area from watersheds originating outside of the park will need strategic multiorganisational collaboration.