A Bay of Islands oyster farmer says he risks being driven out of business by shellfish thieves after more than 30 years in the industry.
Public health officials are also concerned about the thefts, saying the stolen oysters could make people sick because they were taken when the Bay was closed to shellfish harvesting because of possible contamination.
Steve Van Veen, who owns an oyster farm in the Waikare Inlet, has been hit by thieves three times in the past month and about $1000 worth of shop-ready shellfish was stolen each time.
Van Veen said he had been farming oysters for 34 years and had lost just three bags of shellfish in the first 30 years.
''But it's got really bad lately. Whoever's doing it is taking them to sell them, it's not just for a feed.''
The thief or thieves were targeting the shellfish that had been harvested, separated, placed in mesh bags and left on racks to fatten up until they were ready for market.
''You've done all the work and spent all the time and money getting them ready to go, then somebody just goes out and helps themselves. It makes it tough,'' he said.
''The way it's going it could make the business unviable. At $1000 a hit I'm losing $600-$700 a week. That's a person's wages.''
Van Veen said people who ate stolen shellfish were also putting their health at risk because oysters could cause illness if harvested at the wrong time, for example, after heavy rain.
People who bought oysters illegally had no way of knowing if they had been harvested at a safe time.
Meanwhile, another farm was raided this week in Te Puna Inlet at the other end of the Bay.
Owner Pene Waitai, a lifelong oyster farmer, said eight trays — each containing about 25 dozen oysters — had been stolen on Monday night. The theft would cost his family business more than $1000.
The oysters had been left on a pontoon overnight and were about to go back into the water because the Bay was closed to harvesting.
''I sometimes catch guys on the farm and tell them they can't help themselves but I've never had full trays taken before. They seem to think it's okay to take from farms, it just doesn't get through to them. A lot of farms are small family businesses and it's hard work. There's plenty of wild oysters around, why don't they pick their own?''
Waitai suspected the stolen shellfish were being sold to friends and via word of mouth.
Van Veen has reported the Waikare Inlet raids to the police but said preventing oyster thefts was difficult. Friends had told him he needed to stay on his farm overnight and keep guard.
''But then what happens when you're out there, someone comes along and there's a confrontation?''
To make matters worse the thieves were taking the oysters then ditching the mesh bags in the inlet. The bags were washing up onshore, creating an eyesore and a hazard for marine life, Van Veen said.
Oysters are filter feeders, which means they absorb everything in the water, including bacteria washed off the land from farms and septic tanks.
Brad Novak, medical officer of health at Northland District Health Board, said oyster farms were generally closed for 28 days after heavy rain because of potentially high levels of E. coli bacteria.
Eating shellfish from a closed area could cause vomiting, diarrhoea, abdominal pain and cramps.
Anyone suffering those symptoms after eating questionable shellfish should seek medical advice by calling Healthline or Northland's on-call health protection officer on (09) 430 4100.
Catching oyster thieves is difficult but it has been done.
In 2017 Whangaroa oyster farmer Owen Robertson lost half a tonne of the shellfish in one night and, after after being unimpressed by the police response, started his own investigation.
He eventually tracked down CCTV footage, which led to a former employee. Robertson found some of his sacks and oysters at the man's property in Totara North.
Matthew Smith pleaded guilty in the Kaikohe District Court to taking five bags of oysters and was ordered to pay reparation, but that still left Robertson out of pocket for the other 33 bags taken on the same night.
Robertson then took the case to the Disputes Tribunal, which ordered Smith to pay another $1815 for the rest of the oysters.