Cyprinus carpio

Threats Status

Unwanted Organism

Common Name(s)

Koi carp




Koi carp occur in still, warmer water in lakes and rivers. They have a high tolerance of poor water quality (and also contribute to water quality deterioration). Koi are opportunistic feeders, including various aquatic plants, insects and eggs and juvenile of other fish species in their diet.


Koi carp can superficially resemble goldfish except that they grow to larger sizes (in New Zealand up to 10kg and 75cm long) and have two pairs of whisker-like feelers, also called barbels, at the corner of their mouth. Koi carp are highly variable in colour, often accompanied with irregular blotching.

Similar Species

Goldfish (Carassius auratus), grass carp (Ctenopharyngodon idella), silver carp (Hypophthalmichthys molitrix), koi/goldfish hybrid

Threat To Plants

Koi carp uproot aquatic plants during bottom feeding, which also has a negative effect on water quality as sediments are stirred up and muddy, turbid water results. Due to their feeding behaviour they also have indirect negative impacts on native plant, fish, invertebrate and some bird species.


Throughout Auckland and Hamilton, spreading into Northland. Isolated populations exist in Whanganui, Hawkes Bay and Wellington. Koi carp have been eradicated from the South Island.


Weight: <5kg; body lenght: <60cm

Year Introduced


Reason For Introduction

Thought to have been accidentally imported as part of a goldfish consignment.

Colonisation History

Koi carp were probably initially released into the wild accidentally from private ponds during large scale flooding. Wild stocks of koi carp were first found in the Waikato River in 1983 by which time they had likely established a breeding population. Further illegal introductions for the purposes of coarse angling have occurred elsewhere, as isolated populations have been progressively discovered throughout New Zealand (in Nelson 2000 and Manawatu 2001).

Control Options

Pond drainage, netting, cube root powder