Callout for known koi congregation sites

Landowners are being asked to share their knowledge of koi congregation sites in the Waikato region.

Waikato Freshwater Biosecurity Coordinator Michelle Archer last week provided an update to the Integrated Catchment Management Committee on the council’s and the Department of Conservation’s four-year koi carp programme, which has received funding of $250,000 from the council and $488,750 from Waikato River Authority.

In a presentation to the committee, Ms Archer said she was working with key organisations, landowners and stakeholders to understand the locations of koi infestations so contractors could target the sites in spring when koi movements intensify for spawning.

“We ask that if anyone knows of any canals or drains or waterways in which these fish congregate then they let us know,” said Michelle.

“Koi control is dependent on understanding the locations of infestations and potentially doing targeted mass removal of this pest fish.”

One milestone of the project is the completion of the Priority Pest Fish Infrastructure Review, which was presented at the meeting.

Michelle said the review looked at existing pest fish projects in the Waikato region and listed sites for potential new projects to protect indigenous biodiversity values and existing koi free lakes.

“In the next six months we’ll be looking at what is needed to install koi barriers at the top three identified sites at Lake Rotomanuka and tributaries to Lake Waahi and Waitomo Stream,” said Ms Archer.

The koi programme has included environmental DNA (eDNA) surveillance at key sites in the Waikato region, including Lake Maraetai, Waitomo Caves and Lake Rotoroa, and estimating the biomass of koi carp in the lower Waikato using drones.

Surveillance of koi will continue, Michelle said, including collecting eDNA samples at 12 lakes throughout the region that are visited monthly as part of the council’s routine lakes monitoring.

“These lakes are presumed to be pest fish free, but we have had no formal surveillance recently to confirm whether that is the case.

“eDNA sampling is such a valuable tool for understanding the extent of species, as it can detect all species of plants and animals. For example, we had reports of a large orange fish in the Mokau River with concerns it was koi, but the DNA analysis confirmed it was a large goldfish.”

The use of eDNA sampling also helps to build a greater understanding of other invasive species, aquatic and terrestrial, throughout the region.

Integrated Catchment Management Committee Chair (North Stu Husband) said koi were an important issue for landowners in river catchments and he hoped they would take the opportunity to help the koi carp programme team identify and understand problem areas.

Locations and photos of known koi congregation sites can be reported here.