Making a game plan to improve the whenua

From rugby league to research on improving water quality, Tawera Nikau is involved with multiple projects on his farm land in the Waikato. Sheryl Haitana talked to him about Maori plans for koi carp control and getting involved with the science of riparian planting.

Nikau Trust owns 88 hectares (ha) that borders Lake Waikare, the most degraded and contaminated lake in the Waikato Region, due to an invasion by koi carp.

The best tomato plants Tawera Nikau’s grandmother ever grew were planted on top of fish heads.

It’s that ancestral Maori knowledge that has inspired Tawera to kickstart a business harvesting koi carp out of lakes in the lower Waikato and turn it into organic fertiliser, pet food, berley and bait products.

New Zealand produces high value niche products, and koi carp could be another one – as it’s a delicacy in Japan and China, Tawera says.

An extensive riparian margin has been planted between the farmland and the lake edge as part of the Trust’s environmental plan.

Tawera’s family owns 88ha at Ohinewai, which borders Lake Waikare, the most degraded and contaminated lake in the Waikato Region.

Tawera lives onfarm and is actively involved in the management of the land and numerous restoration projects for the Lake. Tawera also chairs Riu o Waikato (The valley of the Waikato), a collective of local marae who have secured the first commercial licence to harvest koi carp on a large scale.

“We have 14 lakes in the lower Waikato and they are all infected with koi carp, doing immense damage to our native species, our eels and our waterways. When you talk about pollution one of the key influences on water quality is koi carp.”

They’ve got a processing facility employing six people and have two boats out fishing on Lake Waikare harvesting koi carp in nets, which will be scaled up in the next few years when the products are tested and ready for the market.

It will not only provide a solution to reducing koi carp numbers, but it’s creating jobs for their people and producing great products, Tawera says.

“It meets a lot of targets, environmentally, socially and culturally. We are ticking all the boxes, eradicating koi carp, putting stuff back into the ground that needs to be there.

“The lakes are all infected with koi carp and they do a lot of damage. It makes sense to help eradicate the koi carp and produce a product where there is zero waste.”

Using their Mātauranga (ancestral knowledge) together with scientific evidence to create sustainable products is exciting, Tawera says.

“For us as Maori, the fertiliser is a classic example. My grandmother used to have fish heads under her tomato plants and they were the best tomatoes. Everyone raved about them. We grew the best kamokamo because we used all the fish and eel heads – it’s free, it’s organic.

Aligning that knowledge with the proper testing and support is really important.”

The Nikau Trust has used a batch of fertiliser on one of their maize blocks this year.

“We didn’t use any other fertiliser, it’s looking a lot healthier, a lot greener,” Tawera says.


The Trust finished leasing out their land to a dairy farmer two years ago and now grow maize and grain for Corson (for more details on this, check out the Corson maize publication).

The koi carp control is part of the Trust’s wider environmental plan, which has involved land use change from intensive dairying to growing crops and a riparian project for the lake.

“The trust has been really instrumental in looking at different ways of doing things from an environmental wellbeing perspective.”

They started doing riparian plantings and removing willows, but the Trust wanted long term sustainability and wanted to partner with credible institutions to record evidence of the effect of what they were doing was having on the lake, Tawera says.

“There are a lot of things happening in this space that the Trust has been at the forefront of and we have built some great relationships.”

Nikau Trust has partnered with stakeholders in a research programme which is investigating the potential of mānuka and other native species to reduce the impact of farming activities on the waterways, to provide diversified incomes to farmers, and to improve the cultural relationships of the communities with the lake. Lake Waikare is the most degraded and contaminated lake in the Waikato Region. Inputs of nutrients, pathogens and sediments from the surrounding farming activities, the deforestation of natural vegetation, and the Flood Regulation schemes since the 1960s, are the main drivers that led to the low quality of the lake. The strategic importance of Lake Waikare and the Whangamarino wetland as the lungs and kidneys for the Lower Waikato Region are recognised by local Iwi, since in the past the lake was a source of sustenance for the whānau of the region.

The research programme is funded by Waikato River Authority, Waikato Regional Council (WRC), Vision Mātauranga Capability Fund, and ESR SSIF Funding. With these funds a programme was created in collaboration with WRC, Waikato District Council, Nga Muka Development Trust, Te Riu o Waikato, Waikato-Tainui, Matahuru Marae, Nikau Farm Trust, and EcoQuest Education Foundation.

The project has planted 40,000 plants in 4ha at Lake Waikare, a mixture of native species typical to the area.


The objective of the project is to investigate the potential of mānuka and kānuka to reduce pathogens and nitrate leaching. The properties of these plant species were previously proven in laboratory and greenhouse experiments, but it has proved challenging to test it in the field, ESR scientist Maria J Gutierrez- Gines says.

“We are trying to understand which plants work better and create scientific evidence that proves the potential of native plants to mitigate water pollution.

“It has proved to be very challenging. It’s very easy to control what you want to measure in the lab, but one of the things we wanted to measure in the field was runoff, but measuring runoff has proved to be very complicated because the site is a swamp in winter and in the summer the soil just cracks so there is no runoff.”

In collaboration with Waikato University they are now trying to measure the different layers of the soil and trying to understand how water and nitrogen moves in the different layers of the soil.

The real time data of movement of water in the soil, helps to work out how nitrogen moves in the soil.

“All of the plants suck up nitrogen, but different plants have different nitrogen needs. Manuka and Kanuka affect the bacteria transforming organic nitrogen into nitrate.”

They are also looking at which plants establish better in the area and are studying the insect biodiversity, Maria says.

“As soon as you fence off the waterway and remove livestock, the insect biodiversity increases in just one year.”

The riparian planting has been a whanau project, with everyone coming out to help plant, giving people the access to be on their land, Tawera says.

“A lot of our whanau (family) are living in the cities and they haven’t been out to the farm since they were kids, so it’s neat they can come back with their kids and grandkids.

“My grandfather used to tell us about being able to see the bottom of our lake and swimming in it as a kid.

“The next generation coming out and helping plant riparian species might be lucky in 40 or 50 years time to see some of their work pay off with improved water quality.”