In news– South Africa’s sandfish are on the brink of extinction.
- They are migratory freshwater fish found only in South Africa that can grow to over half a metre in length.
- They sport a pronounced downturned mouth, which is used to graze algae off rocks and to grub in mud and sand on the stream bed.
- As one of the largest grazers in South Africa’s Doring River system, sandfish keep the rivers clean and the food web balanced.
- They also act as an umbrella species — protecting them indirectly protects river ecosystems and other species that inhabit them.
- That’s by virtue of their migratory life cycle: Sandfish move over long distances of river at different life stages.
- To thrive, they need healthy, connected rivers that hold water year-round and don’t harbour alien species.
- The sandfish has an impressive spawning strategy. It migrates dozens (perhaps even hundreds) of kilometres each year to reach its tributary spawning grounds.
- Sandfish were once abundant and widespread across the Olifants and Doring River systems, but have recently disappeared from the Olifants. Their numbers in the Doring are in sharp decline.
- Catastrophic unseasonal flows due to climate change during the 2013 spawning season likely catalysed this decline.
- The long drought that followed prevented population recovery. Adding to the problem was the presence of non-native black bass and bluegill sunfish.
- Some of the threats faced by sandfish are predation by introduced non-native fishes, the construction of dams that block upstream spawning migrations, extreme climatic events, and rivers that are drying due to climate change, thirsty alien plants, and the excessive withdrawal of water to supply agriculture and towns in arid regions.
- The biggest worry is the lack of juvenile and subadult sandfish in the Doring River. It indicates an ageing population with few, if any, young sandfish surviving the precarious early life stages.
- These conditions, ubiquitous throughout the sandfish’s remaining range, have resulted in bringing the species to the brink of extinction.