Final gasp for 20-million year old fynbos fish
Freshwater fish in the Overberg, Western Cape, are catching the attention of local and international conservationists – in an urgent effort to prevent these often tiny, but very special and unique fish species from going extinct.
Fynbos fish have survived in rivers and streams flowing through the Cape Fold Ecoregion for millennia. For example, redfin minnows have lived here for almost 20 million years, since the Oligocene period – long before humans walked the Earth.
Globally, freshwater fish species are in serious trouble and the Cape Fold Ecoregion is no exception. In fact, a 2021 World Wildlife Fund report found that freshwater biodiversity is being lost at twice the speed of forest or ocean biodiversity. Soon, one in four freshwater fish species could be lost forever if no efforts are taken to reverse the current trend.
Losing our Overberg species
In the Western Cape, and specifically the Overberg, it’s a similar story. Here, fynbos fish, many restricted to a single catchment or even tributary, face a plethora of threats, mainly invasive fish such as bass species, excessive water abstraction and deterioration of habitat and water quality.
The lack of knowledge regarding fynbos fish and the extreme concern for their survival sparked interest from the International Union for the Conservation of Nature (IUCN). A project was launched by the Nuwejaars River Nature Reserve (NRNR) to better understand the fish species close to Africa’s southernmost tip, their distribution and abundance, and the threats they face. The project received funding support from Fondation Segré, through IUCN’s Save our Species programme.
The Nuwejaars Fynbos Fish Project is managed by the NRNR, a not-for-profit company driving conservation, restoration and rewilding across the 47,000-hectare Nuwejaars Wetlands Special Management Area. Of particular interest were three highly range-restricted freshwater fish taxa, namely the Endangered Heuningnes redfin (Pseudobarbus sp. nov. ‘Heuningnes’), Endangered Heuningnes galaxias (Galaxias sp. nov. ‘Heuningnes’) and the Data-Deficient Agulhas kurper (Sandelia sp. nov. ‘Agulhas’). All three lineages are in the process of being described as new species by researchers from the NRF-South African Institute for Aquatic Biodiversity (NRF-SAIAB). What makes them even more special is that they are found nowhere else in the world except in this region.
“In it for the long haul”
According to Ross Kettles, Operations Manager of the NRNR, “While we know these fish occur in the Heuningnes catchment, which includes the Nuwejaars River, wetlands and its tributaries, very little has been documented on these fish species over the years. It could be because they live in the dark, peat-stained waters of the Nuwejaars, and are therefore not often front-of-mind. But also because saving these species from extinction is not an overnight effort. We’re in it for the long haul.”
From the outset of the project, incredible input and support was provided by fynbos fish experts, including Professor Albert Chakona of the NRF-South African Institute for Aquatic Biodiversity, Dr Martine Jordaan, faunal ecologist of CapeNature and Riaan van der Walt from the Fynbos Fish Trust. Over the course of the year, strong connections were also made with Dr Jeremy Shelton of the Freshwater Research Centre, as well as the Grootvadersbosch Conservancy and the Gouritz Cluster Biosphere Reserve, which are also working to protect their own threatened species of fynbos fishes endemic to the Breede and Gouritz catchments.
The value of partnerships in the conservation sector was emphasised by Dr Jordaan: “Conservation is not only the mandate and responsibility of the provincial conservation agency, it is a team effort. Landowners and NGOs have a critical role to play in conservation, especially in projects such as the Nuwejaars Fynbos Fish Project. While government agencies can assist from a regulatory and planning perspective for these projects, it is the implementers who do the fine-scale work and make the real difference on the ground.”
The Nuwejaars Fynbos Fish Project team sampled nearly 200 sites over 41 km’s of river in 2024. While Agulhas kurpers were most prevalent, only 16 sites were found containing Heuningnes redfins and 42 with Heugingnes galaxias. Galaxias dubius (that had been referred to as Galaxias sp. nov. ‘nebula’ in recent literature), completes the list of the total of four native fish species that occur in the Overberg.
South Africa’s leading fynbos fish expert, Prof Albert Chakona (left), Xiluva Mathebula and Nkosinathi Mazungula of the NRF-South African Institute for Aquatic Biodiversity (NRF-SAIAB) visited the NWSMA earlier this year.
The biggest concerns
The threats to the resident fish community and their habitat also became clear early on in the project. According to project partner, Riaan van der Walt of the Fynbos Fish Trust, “One of the biggest threats is alien invasive fish that were brought in for angling in the 1930s, particularly the bass species. In the Nuwejaars catchment, bluegill sunfish and Mozambique tilapia were the most common invasive fishes, with the latter potentially competing for resources. Spotted bass, a predatory species, was also found at a number of sites. Both the native and non-native fishes have considerable overlap in their habitat use. This makes the native fishes easy prey to the introduced predators. Common carp, a species known for degrading water quality, was also found in some of the sampled sites.”
On the upside, experts believe that the inky, dark waters of the Nuwejaars could also be the saving grace for fynbos fish. Predatory fish such as bass mostly hunt by sight. But in these dark waters, indigenous fish have managed to survive by hiding from the invasives.
Climate change has also emerged as a major threat in the Nuwejaars. In the last two years alone, the region has experienced three flooding events. This has resulted in considerable loss of fish habitat, especially in the smaller tributaries where pools tend to silt up during large floods. This has been worsened by invasive alien trees growing along the banks of the rivers.
Van der Walt added, “The data collected by the team over the year will now be used to develop a conservation plan for freshwater fishes of this area.” The implementation of this plan in 2025 is being supported by the Mohamed bin Zayed Species Conservation Fund.
Environmental education is key
During the project, the team also reached out to a number of local schools, including the Elim Primary School, Mispah School for Learners with Special Educational Needs, Khula Learning Centre, Bredasdorp Primary School and Zoetendal Academy. These children were introduced to freshwater biodiversity, including the fish species.
According to Kettles, it’s not only children who play a role in protecting fish. Land users and farmworkers, too, are a vital cog in the wheel. Kettles gives advice on how to protect fynbos fish: “A starting point is to not relocate or stock non-native fish in dams, rivers or streams. Pollution will also affect these tiny fish, so please don’t pollute or leave litter which can end up in river systems.”
Aside from the Fynbos Fish Project, the NRNR is also restoring large sections of the river and wetlands, by removing invasive alien plants. This in turn is helping to bring about healthier ecosystems for all biodiversity, including freshwater fish.
Kettles says, “More than anything, we want people to know about and take pride in our region’s fynbos fish. The more we know, the better we can help prevent their extinction, especially under our watch.”
IUCN Save Our Species aims to improve the long-term survival prospects of threatened species.
It also focuses on supporting the species habitats and working with the communities who share this habitat. It achieves success by funding and coordinating conservation projects into multiple initiatives across the globe.
This project is supported by Fondation Segré through IUCN Save Our Species. Its contents are the sole responsibility of the Nuwejaars River Nature Reserve and do not necessarily reflect the views of IUCN or Fondation Segré.