For decades, an invasive seaweed has made a home in Akaroa Harbour – threatening to endanger indigenous kelp and disrupt the ecosystem. Now, mana whenua is using it to fund its own removal and beyond by exporting the sought-after wakame as a snack food. The circular economy that is regenerative, financially sustainable and ecologically responsible. Mike Thorpe reports.
When Rik Tainui grew up at “the Kaik” (Ōnuku) in the late 1950s, he says he didn’t have much – and yet he probably had more than he needed. The Akaroa Harbour saw to that – as it had done for the 26 generations before Rik, who whakapapa to Ōnuku Marae on Banks Peninsula.
“It’s known as Te Pātaka o Rākaihautū,” Tainui says.
It translates to the “food basket” or, more accurately, “the great food storehouse of Rākaihautū”.
“Growing up here, I could go to the main wharf in Akaroa and I could catch a couple of red cod, probably in 10 or 15 minutes. This was a fishing village, you know? There was always fish to catch.
“My grandson Cole, earlier this year, went out for his 11th birthday [on his Auntie Pip and Uncle Jim’s] boat with four of his mates, all around the harbour, two-and-a-half hours – two fish. So that tells you something about the difference between when I was a kid and what’s happening now.”
Tainui says in 2026, there are fewer fish in the harbour and many more problems.
One of the bigger issues has no known solution. The invasive seaweed undaria pinnatifida found its way into New Zealand waters some time before 1987 and into Akaroa Harbour in the 1990s. It is known to compete with indigenous kelp – such as macrocystis, or giant kelp. Removing it is expensive, labour-intensive and, in the long term, ineffective.
“We’ve got 250 tonnes on this harbour, and you can’t get rid of it because as soon as you pull it off, the spores go out and it just grows again,” Tainui says.
The cost of removing it is high – the cost of leaving it is higher.
“The undaria is just swamping everything; it’s like gorse, it just takes over.”
The harbour needs its native seaweed – macrocystis – to flourish to help the ecosystems thrive.
“It’s the fastest growing plant on the globe. It’s incredible for creating space for mahinga kai [food resources],” Tainui says.
Undaria stymies macrocystis by occupying space that the indigenous giant kelp requires.
Almost by chance, Tainui and his rūnanga stumbled upon a sustainable resolution that saw an unwanted pest reveal itself as a treasured gift. The undaria in Akaroa Harbour is a highly sought-after, organic commodity. Put simply, it’s export-quality food: the seaweed known around the world as wakame – a staple of Japanese and Korean cuisine, valued for its savoury, umami flavour and rich mineral content.
“I attended the National Seaweed conference 12 months ago with Carmelle Hine-Mārama [Ngāti Tūwharetoa],” Tainui says.
“Hayley Fraser-Mackenzie from Ceres Organics was on the door and we accidentally hadn’t paid. And we got into a conversation, ‘So, where are you from?’ blah, blah, blah. She said, ‘Any chance you could supply us with seaweed?’ I said, ‘We haven’t grown any yet!’”
Tainui assumed she was talking about macrocystis.
“She said, ‘You’ve got another seaweed I know that we would love to get our hands on’ [the undaria].”
And so began a partnership that could have lasting benefits to the rūnanga (Ngāi Tarewa) of Ōnuku Marae, Akaroa Harbour – and, it seems, consumers of the wakame.
When Ceres introduced Premium Seas to the collaboration in January this year, it was “game on”. Premium Seas is a 50/50 venture partner and is overseeing the first commercial harvest.
Chief executive Lucas Evans is hands-on. He and his team were sorting through the undaria, splitting it before it entered the drying process.
“This undaria is sort of moving on towards the end of the season, so it’s quite mature, which is great in terms of it being large. It’s efficient because you’re interacting with one piece of seaweed and it’s a large piece as opposed to several small bits. The downside of that is we have a thicker mid rib or stipe, and that means that we’ve got to split and make sure it’s not too thick, because it takes longer to dry,” Evans says with knife in hand.
The sorting tables and drying cabinets are literally a stone’s throw from the water, near the entrance to Ōnuku Marae. The facilities are in their early stages but Evans and his wāhine Stef Evans (Ngāti Kahungungu) bring great experience to the operation.
“You’re continually quality-checking. We’re looking for debris, crustaceans, shell, dirt, seaweed that doesn’t present well, and removing it. And then we’re washing it, so we’re trying to just identify the best pieces that make sense to work with,” Evans says.
The first two harvests brought in more than 1000kg of wakame and Evans says the quality is “very good”. He’s also impressed with the divers, who are learning from scratch.
“Some of the divers are only 16 and have not spent a lot of time in the water, those that have done the diving before have typically been engaged to work on the removal. As opposed to removing for a commercial activity,” Evans says.
“That’s a learning curve, but to their credit, they’re all enthusiastic about it because it’s solving a problem that they have at home [Ōnuku], and they’re front and centre. They’re being paid well as well, they’re being looked after.”
Tainui says he and those connected to the project had their “fingers and toes crossed” that the first harvest would be a success.
“When I saw Lucas’s eyes light up, I knew we’d hit the jackpot. And we’ve only just begun,” Tainui says.
It is a jackpot because the undaria operation could provide a clear path forward for future generations to continue the kaitiakitanga [guardianship] that they have inherited. Being involved in the harvest of the kelp gives them a direct connection to that responsibility.
“We’ve got to hand over to these young people so they actually need to know about the marae and the connection with the harbour and the connection with history and the connection with ancestors and that’s actually quite hard for young people to get, unless they’ve got really connected whanau,” Carmelle Riley says.
Riley has worked alongside Tainui throughout the Ōnuku Rūnanga/Premium Seas & Ceres Organics seaweed venture process and has a passion for helping young people and families stay in the area – with sustainable futures. She takes enormous pride in seeing the rangatahi (youth) involved in the venture’s first harvest.
“They just talked about the peace [underwater] and they talked about the fact that they knew that they were pulling up the undaria and it was a weed and it was going to make a difference. And, interestingly, none of them liked to eat it! Which we all laughed about,” Riley says.
Diving for the kelp was the first wave of employment, but Evans can see that expanding.
“If things go the way that we hope, then we’ll see a longer season next year, and then those that are working on it now can move into jobs that are, indirectly, related,” he says.
“Could be marketing, could be IT, managing websites, product development, other product processing, compliance, food control plans, biosecurity plans, all these other plans that we look after now that I’d love some help with.”
The project has an initial two-year pilot to prove that it can work and to understand how it can scale up.
“We’re lucky we’ve got a great partner in Ceres Organics, they’re in here and they’re working really, really hard,” Tainui says.
As chairman of Ōnuku Rūnanga and as a proud Ngāi Tarewa descendant, Tainui wants to see the harbour that he grew up on restored.
“We’ve taken from this moana for 800 years. To be honest, we’ve done very little to give back. My thing is, this is our time. We’ve got money, we’ve got the resources, and we’ve got the connections that we can use to actually make a difference, not only for us, but for everyone on Akaroa Harbour.”
Mike Thorpe is a senior multimedia journalist for the Herald, based in Christchurch. He has been a broadcast journalist across television and radio for 20 years and joined the Herald in August 2024.