KNYSNA NEWS - The ink had not quite dried on a Knysna-Plett Herald (KPH) article of fish going belly-up in Groenvlei near Sedgefield when more reports of dead fish in the region came streaming in. In the Groenvlei case the reason turned out to be an excessive carp population, but it seems elsewhere in the Garden Route estuaries are experiencing similar die-offs and the culprit this time is something completely different.

On 31 January, KPH reported that a group of Groenvlei and Sedgefield locals and conservationists were afraid a second fish die-off similar to that of October last year would hit Groenvlei's waters in coming weeks, citing the uncontrolled carp population as the cause. Authorities and scientists concurred and said a collaborative effort is under way to solve the issue.

Bow hunters, nets used
In the past, bow hunters and nets were used to control the carp population, but with the nets being destroyed by the 2017 Knysna fires and the bow-hunting programme ending in 2018, the carp continue to wreak havoc. The hardy fish is said to turn up sediment, among others, by way of feeding, which in turn releases age-old nutrients into the waters, upsetting the ecology.

Both CapeNature and the SA Institute for Aquatic Biodiversity (SAIAB) are working on the problem, they said, with the institute's chief scientist Prof Olaf Weyl adding that SAIAB is part of a larger research group working on the issue. Other partners include Nelson Mandela University, Sanparks and concerned members of the public, Weyl said.

Great Brak estuary also a concern
Elsewhere in the Garden Route, Cobus Meiring of the Southern Cape Landowners Initiative (SCLI) said the regular fish die-off in the Great Brak River estuary is also of concern.

In a press release on 7 February, Meiring said the primary problems within the Greak Brak's waters include "reduced run-off from the catchment due to drought and a possible change in climate, severe invasive alien plant stands in the watercourse, too many dams and over-extraction of freshwater for various uses, including agriculture and human consumption."

A collaborative effort
According to Meiring, a collaborative effort by the Breede-Gouritz Catchment Management Agency (BGCMA), Table Mountain Fund, Garden Route District Municipality and the SCLI has a chance of putting a halt to the Great Brak estuary's problems. 

"These organisations are joining forces and resources in an effort to improve the ecological wellbeing of the river and estuary," he said.

The first step, said Meiring, would be to inform landowners of the pending situation. "Areas upstream of the estuary, that are particularly badly affected by invasive plant growth, will be mapped and earmarked for clearing. Ultimately measures will be put in place in order to measure the flow of water into the estuary, and to determine where the state of the Great Brak River can be improved over time," he said.

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