Whilst visiting Strandfontein Sewage Works we noticed that their were number of large dead carp in the settling ponds. We then went on to Facebook and saw that Zandvlei had experienced the same thing.
Zandvlei then had some private testing done and got the following results: “We have had feedback from Georgina the vet from the Two Oceans Aquarium who has very kindly assisted us in trying to get to the bottom of the carp deaths. She has not yet confirmed (this will take a few more days and some funding from us, as well as the assistance of a private lab), but she suspects that it is the Koi Herpes Virus. This would explain why only carp have been affected.
This may have been caused by an introduced specimen, but many populations of carp carry the virus anyway. Sometimes when the fish are stressed, particularly post spawn, or in water warmer than 25 degrees Celsius, the disease manifests.”
Carp are native to central Asia. Cyprinus carpio was initially introduced in the 1700s by British colonists. The first official introduction took place in 1896 when C. carpio were imported from England to the Jonkershoek hatchery in the Cape.
People need to be aware of the fact that some actions no matter how well intentioned they may be, can under certain circumstances have disastrous effects.