The Department of Conservation (DOC) may be close to eradicating the environmental threats posed by koi carp in the western Bay of Plenty.

Working with Bay of Plenty Regional Council, Tauranga DOC staff have managed to remove these fish from almost all known locations, with only one small pond near Katikati still on the list.

An eradication project at Kauri Point near Katikati last week saw the removal of koi from two large ponds on a private orchard.

These contained large numbers of the invasive fish, classified as a noxious species under freshwater fisheries regulations, which were historically released to beautify ornamental ponds but are now known to be a serious threat to the environment.

The third and final pond on the property will be targeted next year. Koi were also found in the Waimapu Stream in Tauranga in 2005 but were removed, and no further sightings have been confirmed there.

Eradication of the fish will be a relief to many. Koi degrade water quality through stirring up sediment, increasing nutrient loads and algal concentrations making the habitat unsuitable for other animals and plants.

Koi also prey on native fish species, insects and plants, and can out-compete other species for food. Koi are impossible to control once established in free-flowing watercourses. Large areas of Auckland and the Waikato are infested with the fish which have gained a foothold in rivers and streams and are now sadly beyond control in those regions.

Western Bay landholders who suspect they may have koi on their properties are strongly encouraged to report sightings to DOC in Tauranga or to the regional council so that eradication can be completed. Intentionally moving or releasing the fish can result in a prosecution, however DOC is able to work together with landholders to remove the fish safely.

Koi carp can be confused with goldfish which are not considered an environmental threat. You can tell the difference by looking at the mouth; koi carp have whiskers or barbels at the mouth (two pairs), and are much bigger than goldfish which only grow to a maximum 25cm and have no barbels.

For more information, and if you have seen koi carp, please contact DOC in Tauranga on [email protected] or call 07 578 7677