• Post category:2016 / News
  • Reading time:3 mins read
11 October 2016 | By Ana Nunes

A recent study, led by C·I·B Post-doc Ana Nunes, highlights the danger of an invasive freshwater crayfish reaching the Okavango Delta and the potential devastating consequences for the ecology of this UNESCO World Heritage Site.

Although there are no native freshwater crayfish found in aquatic bodies of continental Africa, the Australian redclaw crayfish (Cherax quadricarinatus), one of the species that has been introduced in the continent, has quickly spread throughout southern Africa, especially in Zambia. Whereas populations exist mostly in Lake Kariba, a new population was recently reported on the Barotseland floodplains, in the upper Zambezi River, an area with pristine habitats, which seasonally connects to the Okavango Delta.

The Australian redclaw crayfish (Cherax quadricarinatus)
The Australian redclaw crayfish (Cherax quadricarinatus) (Photo by Ana Nunes)

While not much is known on the specific impacts of the Australian redclaw crayfish, freshwater crayfish invasions often cause changes at various trophic levels of aquatic ecosystems. These can, for example, disrupt aquatic plants that grow in the water and macroinvertebrates (small animals without a backbone that can be seen with the naked eye), as well as cause disturbance of fish breeding habitats.

As such, if redclaw populations manage to spread and reach the Okavango Delta, this will be a serious threat to one of the largest intact wetlands in the world and, for now, free of invasive aquatic animals.

According to Nunes, “Research to identify the extent of redclaw invasion and the establishment of eradication or control measures are urgently needed. While these will surely be difficult and costly to implement, failure to control this invasion may have devastating consequences for the Okavango Delta.”

The study was published in the scientific journal Frontiers in Ecology and the Environment.

Read the article by Nunes and colleagues

Nunes, A.L., Douthwaite, R.J., Tyser, B., Measey, G.J. and Weyl, O.L.F. (2016) Invasive crayfish threaten Okavango Delta. Frontiers in Ecology and the Environment 14(5): 237–238

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For more information, contact Ana Nunes at ananunes@sun.ac.za