Koi Carp
Koi carp (Cyprinus carpio)
This brightly coloured member of the Cyprinidae family is probably native to Asia, although it has been introduced so widely and for so many centuries that its precise origins are uncertain. Today, it occurs on every continent except Antarctica. It is not known whether their introduction here was deliberate or accidental, but feral breeding stocks were first noticed in the Waikato in 1983. They are now common throughout the lower Waikato system, and also occur in a few streams around Auckland and in isolated ponds elsewhere. A single dead specimen has been recovered in Northland and they were discovered in the Manawatu in 2001. The first South Island record of koi carp occurred in Nelson in 2000, although all the South Island populations have now been successfully eradicated.
Wild carp tend to be an olive green colour, but the New Zealand stocks are derived from the highly bred ornamental Japanese koi and thus often exhibit a calico pattern of black, red, orange, gold and white blotches. So far, our feral stocks have not reverted back to the wild colouration. Although their colour pattern is a useful distinguishing characteristic, they also have two pairs of barbels that the other Cyprinidae found here lack.
Koi eat a wide variety of organisms, including both plants and animals. One way they feed is by sucking up and expelling material from the bottom, filtering out edible material as they do so. This habit means they can greatly increase the turbidity of the water because they are constantly stirring up the substrate.This makes waterways unattractive, reduces the abundance of aquatic plants, and can render the water unsuitable for swimming or drinking even by livestock. In other countries, koi have caused so much damage to waterways that vast amounts of money and effort have been spent trying to eradicate them; unfortunately these have largely been unsuccessful. Although similar problems have not yet occurred in New Zealand, the spread of this fish should certainly be minimised.
