Te Rui o Waikato have big plans for Lake Waikare.

Years of environmental degradation caused in part by koi carp has turned Lake Waikare toxic.

Now Waikato tribal group Te Riu o Waikato are determined to change that as they look for ways of eradicating the pest fish from the lake once and for all.

The group, which comprised 15 marae held an information day at Matahuru Marae less than a kilometre from the lake involving speakers from the farming community, commercial operators, iwi and environmental groups.

Lake Waikare is infested with the pest fish koi carp.


Lake Waikare is infested with the pest fish koi carp.

Te Riu o Waikato chairman Tawera Nikau said the day had been talked about for some time as the group's members looked for ways to restore the lake.

"The way forward for Te Riu o Waikato and the marae here is that we want some action. Our next process is the finalise off our [commercial fishing] licence with DOC. We'll have another meeting in a couple of weeks because we want to be starting to fish a soon as possible."

They are exploring how the fish could be turned into commercial product, such as fertiliser or fishmeal.

No one knows how many koi carp are in Lake Waikare, but Fish & Game's Dr Adam Daniel estimates it would be a similar number to nearby Lake Ōhinewai, which had 350kg of carp per hectare according to a 2014 study.

Daniel said eradication had never been tried on a lake the size of Waikare. To do so successfully would come with a big price tag.

Even if all carp were removed, agricultural pollution and wind stirring up the mud on the bottom of the lake would still have to be tackled.

"Will removing koi restore Lake Waikare? Not without addressing those other two factors."

While there is potential to develop a koi carp commercial product, any business would have a limited lifespan since the ultimate goal was to rid the lake of the fish, he said.

"The market is there and you could probably make big money now, but in terms of using it as a restoration project, you need someone who is going to carry the can for 20 to 25 years."

Nikau was comfortable with that problem if it meant a cleaner lake.

"If we run ourselves out of business, then that's what we want to do."

NZ Waterways Restoration director Gray Jamieson said it was possible to eradicate thousands of koi carp using automatic fish feed machines in the lake that distribute poisoned bait pellets.

Netting was also a valid option and the fish could be eaten as long as they were filleted, skinned and soaked in saltwater before cooking.

Jamieson believes koi carp would always remain in the Waikato River because there are too many tributaries and streams where the fish have access.

"But I believe you can make a huge impact in Lake Waikare."

Pacific Biofert managing director Bill Sinclair said it is "not a problem at all" to turn koi carp into a commercial product such fertiliser for the agricultural industry.

"There are masses of uses for this pest product."

- Stuff


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