In total 38 sacks, each containing nine dozen oysters, were taken. The haul would have weighed about 500kg and could fetch more than $3400 on the black market if sold at $10 a dozen.
Normally thieves helped themselves to the growing racks; this time they went straight for the pre-processed shellfish. The oysters had been harvested, declumped and graded, then placed in sacks and returned to the harbour until water testing gave the green light for the shellfish to be sold.
The harbour is currently closed to harvesting which means anyone eating the stolen shellfish risks becoming ill.
The amount taken meant it wasn't someone who needed food for their family, Mr Robertson said.
"They're not stealing for a feed. They're stealing to make money, and they'll make a lot more than I ever will. They didn't have to pay for staff, taxes, water testing, barge fees, licences or any of my other costs."
Ongoing thefts put the jobs of his three workers at risk, two of whom had children on the way. They "worked their guts out every day" with hard work in cold water, but if the farm started losing money the first thing he'd have to do was downsize.
"People complain they can't get jobs or they can't afford food. This affects jobs and put up prices. It also affects the seafood industry because if people get sick they'll blame the oysters and that stuffs up the market. These mongrels put it all at risk."
Senior Sergeant Brian Swann, of Mid North police, said the public needed to be aware that if they bought oysters from the back of a truck they could be putting their health at risk and committing an offence, because the shellfish were probably stolen.
He urged people to call their nearest police station if they were offered shellfish in suspicious circumstances.
■ Email Mr Robertson on anythingood@gmail.com or call police if you have information about the theft.