CapeNature experts are investigating the strange phenomenon of a fish die-off occurring widely in Groenvlei
Lake in the Goukamma Nature Reserve between Sedgefield and Knysna.
Spokesperson Marietjie Engelbrecht said fish and water samples had been taken.
The results were being analysed by various experts and scientists in an effort to inform actions to be taken.
“There is currently a fish die-off event occurring widely in Groenvlei, Goukamma Nature Reserve.
“The dead fish collected in the Groenvlei are mostly largemouth bass and bluegill sunfish, both invasive species from the US, but usually associated with good water quality,” said Engelbrecht.
The other species affected are the two indigenous fish species in the vlei - namely the estuarine round herring and Cape silverside, which have genetically unique populations in the vlei and they also require good water quality for survival.
Invasive carp and Mozambique tilapia do not seem to be affected and are known to be very hardy fishes, Engelbrecht said.
“The reason for the die-off is not yet clear and various tests are being conducted to see what the cause could be.
‘‘As CapeNature is uncertain of the cause of this die-off, we request that the public, as a precaution, not consume any fish out of Groenvlei as they may be toxic for human consumption,” Engelbrecht said.
Knysna municipality spokesperson Chumisa Kalawe said: “We have made our residents aware of the situation by sharing the information from CapeNature on our platform.”