Thirty tonnes of green-lipped mussels are to be dropped in the Hauraki Gulf as part of work to re-establish shellfish beds that were destroyed by over-fishing last century.
The community group Revive our Gulf has used millions of farmed mussels from the Coromandel to restock parts of the ocean floor of the Gulf.
Marine scientist Carina Sim-Smith coordinated the latest drop of mussels in the Mahurangi Harbour.
She said the 30 tonnes, donated by the North Island Mussel company, would be split into three parts and delivered to their new homes over the course of three weeks.
The delivery truck of the first 10 tonnes arrived last Friday without a hitch.
Dr Sim-Smith said the first part of the process required the mussels to be soaked to get rid of any pests.
"When they arrive from the Coromandel they went into the fresh water tanks and they have to sit there for an hour-and-a-half to make sure that any possible fragment of attached pests are killed."
"The mussels themselves are much hardier they can just close up and they won't get affected by the fresh water as much," she said.
A crane was used to move the 10 bags of mussels, weighing a tonne each, to barges which took them out into the Mahurangi Harbour.
Teams of volunteers shovelled the mussels into the water at a specially-selected location.
The next drop of mussels was due to arrive tomorrow and another next week.
Marine biologist Dr Andrew Jeffs, who had studied the project, said mussels were environmental super heroes, filtering and cleaning polluted water, and becoming nurseries for juvenile fish.
He said the impact on the environment had been so positive that similar restoration projects were expected to start soon in the South Island.
"There is strong community interest in the Marlborough Sound and also in Tasman Bay."
"We're pretty close to putting mussels back into those areas on an experimental basis, so within the next year we'll see activity happening in those areas," he said.
The South Island efforts would be lead by the Marine Farmers Association for Marlborough Sounds, and in Tasman Bay by the Nelson Marlborough Institute of Technology.
Dr Jeffs said those projects would learn from the Hauraki Gulf experience, but as they were very different marine environments the methods would need to be adjusted.