Threatened freshwater fish of the thee river
THE THEE RIVER
The Thee River is a perennial tributary of the Olifants River, draining from the Koue Bokkeveld Mountains in the Western Cape, South Africa. It is a freshwater fish conservation priority, as it contains six of the endemic fish species of the Olifants River, two of which are listed as Endangered on the IUCN Red List. The main threats to endemic freshwater fish species in the Thee river are water abstraction and predation by invasive alien Spotted Bass.
A PIONEERING RESTORATION EFFORT
In an effort to eradicate Spotted Bass from the upper Thee River to create a native fish sanctuary, the Fynbos Fish Trust and partners initiated a mechanical bass removal effort in 2010 using spearguns and nets to catch the bass. By 2014, 399 spotted bass had been removed and a small barrier weir was put in place to prevent re-invasion in the future.
A LANDMARK CONSERVATION SUCCESS
Following the removal of the predatory bass, there was a documented and significant recovery of native fish species, and the project was celebrated as a landmark conservation success. Three years after bass eradication, native Fiery Redfin were observed in pools where they had been absent during the bass invasion. This highlights the severe negative impact of invasive bass on indigenous fish and the rapid recovery potential once the threat is removed. Now a decade later, the upper Thee River remains bass-free and a critical refuge for six endemic fish species, two of which are swimming dangerously close to extinction.
FUNDERS AND PARTNERS
