Our rivers are dying — and so are the fish we've never heard of

Mail & Guardian

2 days ago

More than 50 000 litres of sewage spews into South Africa's rivers every second, the result of a failure to maintain infrastructure and outdated wastewater treatment plants that are unable to handle current volumes. (Delwyn Verasamy/M&G)
In May, Jason van den Berg and his team at
The surprising presence of this species, which had not been recorded in the
'These eels have one of the most fascinating lifecycles of any local species, as they live most of their lives in freshwater rivers and dams but migrate all the way to the Indian Ocean to spawn,' Van den Berg said. 'The juveniles then return inland, sometimes travelling hundreds of kilometres upstream.'
For him, such sightings not only confirm the continued existence of a rare species, but underscore the importance of ecological connectivity between inland waters and the sea.
When most South Africans think of freshwater fish, exotic species such as carp and bass come to mind. However, the country's indigenous freshwater life is unique, ecologically important and yet often disregarded.
'From the small and often overlooked straightfin barb to the well-known sharptooth catfish, our inland waters hold an incredible, and often very underappreciated, diversity of native aquatic life,' he said.
Many of the country's native fish species are threatened by habitat loss and pollution while the
'A very big problem for our local fish species is all these exotic fish. People basically feed dams with carp and bass for angling and a fish like bass is a predatory fish,' said Van den Berg. 'They eat all these smaller indigenous fish and their eggs and their fry and it seems that one of the biggest problems that our local fish species face is the exotic invasive species.'
Dam construction, canalisation and poor waste management, can destroy critical habitats and wipe out local populations. Another major menace is the use of illegal gillnets in waterways. They cause 'indiscriminate and widespread destruction', Van den Berg said, with unsustainable harvesting hurting fish populations and also trapping terrapins, otters, birds and even crocodiles.
According to the
The institute's
South Africa has 118 freshwater fish species, of which half are endemic, the report said.
One-third of the country's native freshwater fish species are threatened. Two-thirds of the endemic taxa are threatened and most of these are concentrated in the mountainous Cape fold eco-region.
The report said several localised extinctions of populations of freshwater fishes, particularly those in the genera
Pseudobarbus
,
Sedercypris
(redfins),
Cheilobarbus
,
Sandelia
and
Galaxias
have been recorded. Predation by
'These
Van den Berg noted that one of the biggest hurdles that indigenous freshwater fish species face is that so few people even know they exist or where they still cling to life.
'Their obscurity is part of the problem,' he said. 'Without proper data and public awareness, these species risk slipping away silently — some perhaps lost before we even understand their role in the ecosystem.
Rooikat Conservation is calling on the public to help it fill critical knowledge gaps by reporting all types of aquatic life — from lesser-seen indigenous fish to invasive species like redclaw crayfish as well as crabs, Cape clawless otters and even hippos and crocodiles — to the organisation.
Van den Berg related how a few years ago, he bought a second-hand book on local indigenous fish.
'I was quite stunned, even with the knowledge and experience I had with the bush, to see how many species of fish there were. I think most people just aren't aware of this and there isn't really any awareness, which is why we tried creating a bit of awareness,' he said.
Documenting species is the first step in protecting them, he added. 'If we don't know what's out there, or where it still survives, we can't make informed conservation decisions. Each record helps build a clearer picture of which species are thriving, which are declining, and where urgent action may be needed.'
With
Van den Berg cited examples of valuable reports including an indigenous straightfin barb recorded in a slow-flowing stream near Hammanskraal, with a clear photo and GPS location sent via WhatsApp; a freshwater crab spotted near Rayton, with a photo and GPS location sent via WhatsApp; a largemouth bass caught in a farm dam near Cullinan, uploaded to iNaturalist and an illegal gillnet discovered and removed from the Apies River, with photos and location.
'Many anglers, landowners and others who spend time near rivers and dams encounter species they may not realise are ecologically significant,' he said. 'With just a bit of awareness, a photo and a shared location, members of the public can provide valuable data, helping scientists and conservationists build a clearer picture of what exists and what needs protecting.'
He noted that the poor conditions of freshwater ecosystems in South Africa ultimately affect humans. 'We depend on water for life. If our fishes struggle due to bad water quality, we'll follow suit … The more we toxify and damage our waterways, the more we will suffer as well.'
* Contribute by sending your photo and location directly to Rooikat Conservation via WhatsApp at 076 982 0471.