Saving Sandfish
The quest to conserve South Africa’s most threatened migratory freshwater fish
SWIMMING ON THE EDGE OF EXTINCTION
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.
The Doring River – the last stronghold for the Clanwilliam sandfish
An absence of small size classes indicates widespread recruitment failure, and the big concern is that there are very few rivers that still support healthy sandfish populations. The Biedouw is the last known tributary where sandfish still migrate to spawn reliably year after year.
THE BIEDOUW RIVER
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.
A group of adult sandfish migrate up the Biedouw River to spawn
EMERGENCY CONSERVATION ACTION TO PREVENT SANDFISH EXTINCTION
To prevent sandfish extinction, the Freshwater Research Centre and partners launched the Saving Sandfish project in 2020, which has undertaken Africa’s largest freshwater fish rescue on record, with promising results in the early stages (Cerrilla et al. 2023). Teams of scientists, farmers and local community members have collectively rescued and relocated over 35,000 juvenile sandfish from the Biedouw (where their chances of survival are slim) to six off-stream reservoirs, which were cleared of non-native fish to create sandfish sanctuaries.
Number of sandfish rescued
6
Number of sandfish sanctuary dams established
Once these fish reach a ‘bass-proof’ size of 15cm, they are released back into the wild with tiny PIT tags which allow scientists to track their movements and survival. Nearly 3,000 bass-proof sandfish have been released, and results to date show a 16.4% return rate, and a more than doubling of the size of the Biedouw spawning population.
2,829
Number of sandfish released back into the wild
Number of tagged fish returning to the Biedouw to spawn
RESTORING CRITICAL SANDFISH HABITAT
To secure the long-term survival of the sandfish, a project is now underway to permanently eradicate non-native predatory fish from the upper Biedouw River, reclaiming 9km of critical habitat for the sandfish and four other endemic fish species. The non-native fish will be removed using the piscicide rotenone, and a barrier weir installed downstream to prevent reinvasion in the future. If successful, this will create a long-term sandfish refuge, and an important source population for the species. This project has launched in 2024 with funding from IUCN SOS, the Mohammed Bin Zayed Species Conservation Fund and Bushmans Kloof.
The upper Biedouw River will be restored for endemic fish through invasive species removal
SHARING THE SANDFISH STORY
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.
Biedouw Valley farm worker Pride watches the sandfish migration through a virtual reality headset.
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.
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