University of Otago aquaculture and fisheries programme director Prof Chris Hepburn said the Ngai Tahu-led programme was using university know-how to develop control teams to clear Undaria from natural areas to try to give native ecosystems a chance to recover.
It was a Land Information New Zealand and Jobs for Nature supported Ngai Tahu project and the work now would help the university pass the "baton" to the Ngai Tahu teams.
However, importantly, the present diver-training part of the project created what Maori called a "tuakana-teina relationship", Prof Hepburn said.
In a sense there was a "big brother, little brother" learning relationship where sometimes he was learning from the Ngai Tahu divers and sometimes they were learning from him as they collaborated to control the unwanted invasive kelp species.
First found in New Zealand in the late 1980s, the pest arrived in Otago Harbour in the early 1990s.
There now could be hundreds of tonnes of it in the harbour.
"It’s heaving, Otago Harbour is just full of it," Prof Hepburn said.
"It’s got the classic invasive species traits: quick growing, reproduces a lot, will attach to anything and can grow in a really wide range of environments.
"From fully wave exposed to sheltered, high light, low light, inter-tidal: it’ll do it all.
"It’ll grow on crabs, bottles, on soft sediment we are finding now."
While the seaweed did provide habitat, it was not the same quality habitat that was provided by native species of seaweed, he said.
It outcompeted those native species and hampered biodiversity.
This week, Undaria pinnatifida control programme members cleared the reef in front of the Portobello Marine Lab as part of a training programme under way for Ngai Tahu divers.
Next month, the programme would involve a scientific dive course along the Otago coast on the university research vessel Polaris 2.
The team had so far removed around 23 tonnes of Undaria from the East Otago Taiapure and Otakou Mataitai after having been in the water for 35 days, Prof Hepburn said.
Prof Hepburn emphasised it was a "control programme".
"It’s not like we’re harvesting.
"We’re not just ripping out the big ones," he said.
Each bag of Undaria the control programme removed was carefully recorded so they could map where the pest was removed from in order to create a map of distribution.
It was being removed under a permit and all of it had been disposed to land, where it was composted, he said.
Tangata tiaki for Puketeraki Brendan Flack said the project began a number of years ago, but the recruiting and training of divers began late last year and training would continue next year as well.
Ultimately, Ngai Tahu expected to have close to two dozen divers in the programme, he said.
Previously, there had been extensive survey work to assess how much of the invasive weed there was.
Those receiving training would now continue efforts to control it in the customary protected areas of East Otago Taiapure and Otakou Mataitai.
Soon there would be an extension of the control programme, south to Rakiura-Stewart Island and up the coast to Banks Peninsula, he said.
The issue of Undaria was a growing one for southern coasts, but it was easily overlooked, he said.
Whenever there was a "gap", the pest seaweed filled it, and it appeared to be unaffected by the increasing marine heatwaves, he said.
"Because it’s underwater it’s not that well seen, not like wilding pine or gorse where it’s visible," Mr Flack said.
"But when you see it underneath it’s just phenomenal how that marine environment has changed over the last couple of decades."
