Ministry for Primary Industries compliance manager for Northland Darren Edwards said fish could only be sold by commercial fishermen or commercially-operated fish retailers.
While fisheries officers were unsure how much fish had been sold by the Whangarei women there was about 30kg of fresh mullet remaining while the Kerikeri couple had up to 40kg still for sale.
All the fish was seized as were the vehicles.
The individuals are likely to face prosecution under the Fisheries Act 1996 which carries a maximum fine of $250,000.
Mr Edwards said those caught buying fish from non-commercial anglers were also subject to a fine of up to $100,000.
Officers believe the fish being sold were excess to requirements after fishing trips.
"Fishers need to plan their fishing activities before leaving and to make sure they're aware of the recreational fishing regulations regarding what they can and can't do with their fish," Mr Edwards said.
He urged people to report illegal activity to 0800 4 POACHER.