Pollution biggest threat for fish of a thousand casts
Effluent in the Vaal River is behind die-off of largemouth yellowfish
The largemouth yellowfish, which can grow to more than 20kg, lives in the Vaal River and is an unrelenting fighter when finally enticed into swallowing a fly.
In 2009 a study compiled by the Centre for Aquatic Research at the University of Johannesburg estimated that the annual economic value of yellowfish angling on the Vaal River was about R133m a year.
But fishing tourists are now staying away, because of the Vaal’s pollution. In July the river experienced a mass fish die-off, the largest since 2010.
Fly-fishermen who hunt the largemouth yellowfish call it "the fish of a thousand casts [of the line]", because it is elusive and huge skill is required to catch it. Foreign fishermen come to the banks of the Vaal and pay good money to catch a uniquely SA species.
In July, farmers and locals hauled out thousands of rotting fish from the river, in an effort to clean it up. There have been reports of increased effluent flowing into the river, because of malfunctioning sewage works along its banks.
"Last month for the first time ever, I didn’t guide a single person," says fly-fishing guide Rohan Koegelenberg. "And I am not going to take people out, it is too dangerous."
His fear is that his clients will get sick from ingesting E.coli bacteria that has infested water in the river. Some strains of E.coli infection can cause nausea, vomiting, and fever.
"I have people sitting on the fence; they will only book for the summer once they see what happens with the Vaal River," says fishing guide Mark Yelland.
Besides the more elusive largemouth yellowfish, anglers also come to the Vaal to catch the smallmouth yellowfish, a close cousin and another indigenous species.
There are other species that attract anglers to SA’s third-longest river, including the mud fish and barbel.
No-one knows yet what the effect the recent die-off has had on the populations of these fish.
"It is usually the bigger fish that are affected by these die-offs," says Prof Victor Wepener, director of the School of Biological Sciences at North West University. He was part of a team that studied the last major fish die-off in the Vaal.
What is not yet clear is the cause of the fish perishing recently. Wepener says it is usually due to the accumulation of several factors.
"It is a bit like stretching an elastic band, these fish are already stressed, because of pollution and the dry season," he says. "Then you have a sudden event like a sewage spill and the elastic band snaps."
A sewage spill, with its added bacteria load, sucks the oxygen out of the water.
Tiaan Cronje says he has never seen as many dead fish floating on the Vaal River as he did in July. Tourists are no longer willing to spend some time on the river.
Cronje works for R.E.A.L Adventures, which offers white water rafting from the Free State town of Parys for several kilometres down the river.
"We have the most amazing stretch of river, but now 90% of people who visit opt to do other land-based activities we offer."
Not everyone appears to be concerned about the pollution in the Vaal. Louise Kenny at the Parys Information Centre says that after news broke about the sewage spill and fish die-offs, many establishments offering activities on the river were fully booked. "Some parts of the river were affected by the pollution more than others," she says.
Yelland has competed in fly-fishing contests around the world, and still the Vaal River is a special place for him.
Well known fly-fishing rivers in other countries are often crowded, he says, while the Vaal offers hundreds of kilometres of untouched beauty.
"What we have here is a world class river, that the government is treating as a sewer."
In the coming months the Vaal River, and fish who live in it, might get a reprieve when the rains arrive. The sluice gates at the Barrage dam near Vanderbijlpark are usually opened when it rains and the higher volumes of water released flush pollution from the river system.
The fish in the river spawn in spring. After that, anglers and scientists will get an idea of the effect of the die-off on fish stocks.
"The river has bounced back before, but how often can it keep doing this?" Koegelenberg asks.