Water Research Commission Project K5/2337 and Table Mountain Fund Project 2490

Assessing the effect of global climate change on indigenous and alien fish of the Cape Floristic Region 


Project leader: Dr Helen Dallas (

Project Duration: July 2014 to October 2017

Project team: Dr Jeremy Shelton (FRC and University of Stellenbosch), Dr Nick Rivers-Moore (FRC), Dr Bruce Paxton (FRC), Dr Olaf Weyl (South African Institute of Aquatic Biodiversity - SAIAB), Dr Albert Chakona (SAIAB), Dr Bruce Ellender (SAIAB), Dr Darragh Woodford (SAIAB), Dr Martine Jordaan (CaepNature), Mr Dean Impson (Cape Nature), Mr Riaan van der Walt (CapeNature), Ms Jody-Lee Reizenberg (MSc Student) 

Two aspects of the Cape Floristic Region (CFR) fish fauna distinguish it from that in most other regions: the level of endemism is exceptionally high, but so is the proportion of these endemic species that are threatened. Research carried out over the past two decades or so has addressed the question “why are these fish so threatened?” and it has become increasingly clear that habitat degradation and impacts of alien invasive fish are among the most serious threats. In addition to recent advances in ecological research, there has also been much progress in resolving the systematics of the CFR fishes and we now have a far better hold on what species occur in the region and on what the taxonomic relationships are between these species.

Moving forward into the 21 st Century there is now little doubt that human-linked climate change will come into play as a major additional factor impacting on CFR aquatic biodiversity, including the already-imperilled freshwater fishes. Indeed, climate change predictions for the CFR, a Mediterranean Climate Region, are severe, with significant increases in water temperature and rainfall variability, and decreases in total runoff, forecast for the region. The consequences of these changes are likely to be especially severe for CFR fishes since remaining populations are now largely restricted to headwater habitats where small changes in river temperature or run-off could have dramatic effects on abundance, distribution and species survival. Moreover, the interplay between these predicted hydrological changes and the impacts of alien invasive fish is a further cause for concern, with the distributions of key alien species apparently largely driven by temperature thresholds.

The results of this study will contribute to our understanding of freshwater fishes in the CFR, and inform decisions as to the vulnerability of indigenous fish species to climate change, coupled with the threat of alien invasive fish species. In combination, these proposed activities will allow for an assessment of the level of extinction risk to the indigenous fish communities in the CFR and allow for the prioritisation of river reaches for conservation action.