/ 24 July 2015

Fish in troubled waters

Apple chief executive Tim Cook with rock band U2 as he speaks during an Apple event announcing the iPhone 6 and the Apple Watch in California.
Apple chief executive Tim Cook with rock band U2 as he speaks during an Apple event announcing the iPhone 6 and the Apple Watch in California.

Between the Olifants-Doring and Breede-Tradouw catchment area a number of endemic fish are under threat. These fish-full streams are under tremendous pressure as their waters irrigate the hub of the fruit and wine industries and supply domestic use.

The rivers in the area are home to 10% of all freshwater fish in South Africa, including the endangered Clanwilliam sandfish and the critically endangered Barrydale redfin. 

One of the issues is the propagation of strong alien species that eliminate smaller endemic fish. While predatory fish such as bass and sunfish feast on the smaller fish, there’s also an issue with the “colonising carp that take over the area and use the majority of the resources” according to Christy Bragg, environmental manager of the project.

The Cape Critical Rivers Project is located in the area. Says Bragg: “The Cape Critical Rivers area has huge biodiversity value. We wanted to start implementing innovations in these areas — in this way, we could build resilience and maintain species and water flow before it was too late.” 

In the process, they caught 380 endangered sandfish that were under imminent threat. The sandfish were trans-located to a pristine area where they would be safe form marauding alien species. 

 If the predatory fish find their way into the tributary, the sandfish face extinction. The team therefore worked to ensure that landowners and volunteer groups in high-risk areas are aware of the dangers of alien fish invasion. A GIS system maps the area, making it easy to track and collate content. The information was also used to create a fish field guide and education programmes are now taking place. The department of water and sanitation has shown interest and local communities are getting involved. 

Together with the Freshwater Research Council, they’ve also created a toolkit to help farmers and local communities determine water flow: by law, this should be 30%, but until now it has been very difficult to measure this.

It’s critical to protect the relocated fish. “The main rivers are still jam-packed with alien species. But we’ve started to make a difference in the tributaries, where we can still save species and still have an imprint,” says Bragg.

A Biodiversity Management Plan (BMP) for the critically endangered Barrydale redfin and the recently gazetted BMP for the endangered Clanwilliam sandfish have been put together. This sets a precedent as a legally binding BMP for any freshwater species in South Africa. 

“When we moved the sandfish, we had to leave some behind. We returned to the area that they had been in, and not one of the original population had survived. They had all been eaten — every single one was gone,” says Bragg.