The government has picked six spots to shift salmon farms to within the Marlborough Sounds, saying it would help clean up the seabed and boost production.
Some are at sites where aquaculture is prohibited so the law would have to change.
One of King Salmon's farms in Tory Strait Photo: RNZ
Shifting King Salmon's six farms to deeper water with stronger currents would be more sustainable and productive, the Ministry for Primary Industries (MPI) said.
It could more than triple production and create 300 jobs, as well as being cleaner, King Salmon said.
The Guardians of the Sounds environmental group said the shift would let more salmon be farmed. It would create more pollution that stronger currents would simply spread further afield.
Five of the six proposed sites are in Pelorus Sound. One is in Tory Channel.
King Salmon chief executive Grant Rosewarne said the shift would cost at least $40 million but would be a win-win for everyone.
"There isn't another initiative out there where you can get a better environmental outcome, employ 300 additional people and get a better social outcome as well in terms of being further away from recreation and baches."
Minister for Primary Industries Nathan Guy is now considering new rules under the Resource Management Act to change the Marlborough Sounds resource management plan to allow applications to the district council for resource consents to farm salmon at specific sites.
The consent applications would not be publicly notified, though the council could give limited notification to anyone affected.
The government said the public would get its say now, with public consultation opening today on the proposal and running until late March. An independent board will hear public submissions in April.
"At high-flow sites King Salmon will be able to grow more salmon which means more feed and more pollution," said Ms Pinder. "It might not all land directly below the pens, but the pollution is spread further in the water column."
MPI predicts shifting the farms over the course of about 15 years would boost the local economy by up to $49m a year and create up to 511 jobs.
It said King Salmon would need hi-tech buoys monitoring water quality all the time.
Two farms in Tōtaranui/Queen Charlotte Sound, at Ruakaka Bay and Otanerau Bay, would be shifted; four in Pelorus Sound, at Forsyth Bay and Waihinau Bay; and two disused farms at Crail Bay.
The relocation sites are in Pelorus Sound at Blowhole Point North and South, Waitata Mid-Channel, Horseshoe Bay and Richmond Bay South; and in Tory Channel at Tio Point.