Ministry of Fisheries officers have broken up a family paua poaching network operating along the Kaikoura coast.
Fisheries officers in Nelson and Christchurch say paua has been taken illegally for about five months.
The suspected ringleader, a Vietnamese man, 48, was arrested this week.
Fisheries officers estimate half a tonne of paua has been taken, on-sold and distributed within the Vietnamese, Cambodian and Chinese communities in Nelson, at $30 - $50 per kg.
The man will appear in the Nelson District Court next week.
If convicted of taking and selling paua illegally, he faces up to five years in prison or a fine of $250,000.
Nelson District Compliance Manager Geoff Clark says information about the ring came from a tip-off and more arrests are likely.
Earlier this year, Ministry of Fisheries officers broke up another paua poaching ring operating along Wellington's south coast.
It involved an undercover officer buying more than nine tonnes of paua, valued at about $1.3 million. It resulted in at least 65 arrests.