Conserving South Africa's most threatened migratory freshwater fish
The Clanwilliam sandfish is South Africa’s most threatened migratory freshwater fish, and its ‘Full Migrant’ life history that makes it particularly vulnerable to human-linked impacts, but also an awesome ambassador for healthy, free-flowing river ecosystems. Once widespread throughout the Olifants-Doring River system, it has likely disappeared from the Olifants Catchment, and numbers in the Doring – SA’s last large, wild, undammed river – and its tributaries are in sharp decline leading to its Endangered IUCN status. An absence of small size classes indicates widespread recruitment failure, and the big concern is that there are now only two known tributaries where sandfish still spawn: the Oorlogskloof and Biedouw Rivers.The Oorlogskloof River supports an isolated population of reproducing sandfish sheltered from fish invasions by a waterfall. However, the population there is at risk from species invasions by alien fish present in off-stream dams in the upper catchment.
The Biedouw River sees adult sandfish migrating upstream from the Doring to spawn in spring, leaving eggs that hatch into thousands of young sandfish. Sadly these young fish perish en masse, succumbing to predation by alien fish (bass and bluegill), which is intensified by water over-abstraction. Consequently, each year the adult fish in the Doring mainstem grow older, and with little or no recruitment filtering through to build the next generation, the future for our sandfish looks bleak unless action is taken to boost recruitment and survival to adulthood.
To prevent sandfish extinction, the FRC started the Saving Sandfish project which, through strategic collaboration, has undertaken Africa’s largest ever freshwater fish rescue, relocating over 15 000 juvenile sandfish from the Biedouw to three dams cleared of alien fish to sandfish sanctuaries. When these fish reach a bass-proof size, they are released back into the Biedouw with tiny PIT tags which allow us to track their movements and survival in the hope that they return to spawn the following year, and thereby boost numbers in the wild.
To secure the long-term survival of the sandfish and other endemic species, the project aims to restore the upper Biedouw River Catchment by removing invasive species and co-occurring freshwater fishes.
Rigorous scientific research and monitoring allows us to better understand sandfish conservation needs and measure the impact of our conservation impact. Research is undertaken in collaboration with universities and students, and there are currently two PhD students from the University of Cape Town working on the project.
Creative and strategic visual storytelling is being used to raise freshwater awareness and deepen connections between people and life beneath the surface of our rivers. We are using a blend of visually-rich photo stories, a 10-part web series and a virtual reality experience for land-owners and communities within the catchment.
Saving Sandfish Web Series takes the viewer on a journey into the hidden world of the endangered Clanwilliam Sandfish and the ambitious conservation efforts underway to save it.
- Cerrilla C, Afrika J, Impson D, Jordaan MS, Kotze N, Paxton BR, Reed C, Schumann, van der Walt JA and Shelton JM. 2022. Rapid population decline in one of the last recruiting populations of the endangered Clanwilliam sandfish (Labeo seeberi): The roles of climate change and non-native fish. Aquatic Conservation: Marine and Freshwater Ecosystems DOI: 10.1002/aqc.3785.