A 20-year-quest to commercialise the greenshell mussel has come to fruition with the launch of the world's largest hatchery.
The hatchery in Nelson will be run by seafood company Sanford and a subsidiary that is also part-owned by the government.
They have a seven-year contract worth $26 million to breed the mussels.
At the moment, the mussels are grown from very young shellfish called spat.
Commercial breeding would allow selective breeding for size and taste.
The complex is made up of a hatchery building, a nursery building and three ponds about 1500 square metres in size.