Glowing redfins swarming among the cobbles, a speckled galaxias suspended weightless in the bubble line and a pack mottled kurpers lurking silently in the shadows. Wiley eels grin in their cavernous lairs as night sets in and their hunt begins. Large cyprinids like the Clanwilliam sandfish migrate great distances upstream to their rocky spawning grounds as the winter floods subside. A hundred years ago our fynbos rivers pulsed with fish life, but sadly those days are now long gone.
Low-lying reaches have been degraded by human activities like agriculture, and fish populations decimated by predatory alien fish. Today, our fynbos rivers are largely devoid of native fish species - a depressing realization given that the majority of these species occur nowhere else on the planet. Our sensitive fynbos fishes are backed into a corner like a wounded boxer losing a fight. They have retracted deep into isolated mountain tributaries which are now their last outposts within vast networks of uninhabitable riverscapes. Nearly all of these species have made their way into the pages of the IUCN’s red data list www.iucnredlist.org/, and some are now so rare and isolated that they are literally swimming on the edge of extinction. Again, a depressing prospect, but there may yet be light at the end of this dark tunnel.
In 2012/13, an ambitious conservation project conducted in the Rondegat River in the Cedarberg demonstrated, under the disapproving eyes of its many sceptics, that sections of river can be rehabilitated and cleansed of alien fish. The project was spearheaded by the local conservation authority CapeNature, and monitoring by the South African Institute for Aquatic Biodiversity (SAIAB) revealed rapid recolonization by native fishes and aquatic invertebrates from upstream following alien fish eradication. The project showed that a chemical called rotenone can completely eliminate alien fish, without detrimental long-term effects on the rest of the river ecosystem, and thereby give our native species back some room to survive - an aquatic miracle if ever there was one!
Unfortunately though, miracles don’t come cheap. The 2012/13 project which successfully eradicated alien bass from 4 km of stream and rehabilitated riparian habitat cost in excess of R4 million. While several species are desperately in need of this type of intervention, future projects will rest on our ability to acquire the necessary funds - a tough challenge when working to save small, shy aquatic creatures that fall outside of the conservation spotlight. With Fins in the Fynbos I hope to raise the profile of these unique but globally threatened fishes, highlight their struggles and offer a way to invest in their future by supporting badly-needed conservation interventions.
For information on planned rehabilitation projects and how to contribute visit www.capenature.co.za/care-for-... or contact CapeNature Scientific Services at www.capenature.co.za/contact-u...
For further information on the Rondegat River rehabilitation project visit academic.sun.ac.za/cib/quest/a..., www.tandfonline.com/doi/abs/10..., www.tandfonline.com/doi/abs/10... or contact Prof Olaf Weyl (principal scientist at SAIAB) at www.saiab.ac.za/professor-olaf...
For more information about our unique but troubled fynbos fishes visit www.nisc.co.za/products/49/boo...
22 июл 2024
