SEDGEFIELD NEWS - The great carp problem that transformed Sedgefield's beloved Groenvlei Lake into "Bruinvlei" late last year and early this year has not significantly improved, but the removal of carp has been put to good use by local food-relief initiatives.

In February, CapeNature announced at a public meeting in Sedgefield that a growing carp problem at Groenvlei Lake had finally reached a point where drastic measures needed to be taken to ensure the future prosperity of the lake's natural fish population. 

The lake has two small species of indigenous fish – estuarine round herring and the Cape silverside – but several alien fish species were introduced into the lake by the then-Cape Division of Inland Fisheries prior to 1960. Largemouth bass and Mozambique tilapia were introduced for angling, bluegill sunfish as a fodder fish, and mosquitofish to control mosquitos.

Illegally introduced in 1990s
There had been a healthy coexistence between the indigenous and alien species until recently when the carp, widely regarded as one of the world’s 100 worst alien species and illegally introduced to Groenvlei in the 1990s, began to overrun the indigenous fish. 

The 180 tonnes of carp have led to a fish die-off because of declining water quality, the collapse of a once-outstanding bass fishery, and poor turbidity due to algal blooms.

While the colour of the water at the lake is closer to normal than before, CapeNature has not noticed a decrease in the number of carp yet, as it is still early on in the control programme according to Barend le Roux, landscape manager at the Outeniqua Nature Reserve. 

According to Le Roux, several solutions to the carp problem have been explored, but they continue to combat the problem through gill-netting and bow-hunting. "Johnny Snyman and his team are assisting with the harvesting of the carp and have written permission from CapeNature with strict conditions regarding gill-net use and bow-hunting activities," Le Roux said of a group of locals who are fighting the carp problem.

"Thirteen tonnes have been removed by the volunteer team led by Mr Snyman since 2018, predominantly through bow-hunting activities. The volunteer team has also implemented gill-netting after this has been used successfully in the past."

 Le Roux mentioned that the gill-netting, although a very successful control method, is conducted under very strict conditions with nets specifically designed for Groenvlei. 

"Current field reports indicate that the majority of the fish has been noted to have retreated into very shallow muddy areas, where setting gill nets are less practical," Le Roux said.

Feeding local communities
The upside of the carp proliferation is that it is coming in handy in feeding local communities such as Sizamile and Smutsville, which have been severely affected by lockdown regulations restricting income-generating activities due to Covid-19. 

"Knysna Municipality approached CapeNature to supply harvested carp to communities as a food source," Le Roux said. "Knysna Municipality has been liaising with Gift of the Givers as a partner to the project, who also assisted with the testing of the fish that was found fit for human consumption."

According to Knysna Municipality spokesperson Christopher Bezuidenhoudt, "the whole fish will be distributed by Gift of the Givers, using the Knysna municipal food parcel database to ensure fair and equitable distribution". They have joined hands with soup kitchens and food-relief schemes in Smutsville, who are making use of the abundant source of carp from Groenvlei.

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