Oysters probably aren't high on the hit list of most crooks, but some farmers are shelling out thousands of dollars a year to the maritime crime.
Oyster farmer Paul Wilson told AAP that while each theft was relatively minor, he'd likely lost tens of thousands of dollars over the course of his 45 years in the industry.
"Every dollar counts ... not only are we losing our oysters, we're usually losing the infrastructure that carry them as well," said Mr Wilson, who farms the Hastings River in the NSW town of Port Macquarie.
"It's a three-year project to grow an oyster for sale so it's a long time and a lot of investment in that stock."
It's not just the lost income that has farmers and authorities worried.
Mr Wilson said stolen oysters also posed a health risk.
Wilson's Port Oyster company spends $60,000 a year monitoring water quality to make sure the oysters are safe to consume.
He said if oysters are stolen before they've been checked the consumer has no way of knowing whether they're ok to eat.
"It's definitely a major problem if someone gets sick from stolen oysters when they shouldn't be on the market," Mr Wilson told AAP.
NSW Police's Rural Crime Prevention Team is targeting black market oysters stolen from farmers and sold without food safety controls.
"We need farmers to report the crime," acting Detective Sergeant Travis Ware said.
"We may not always be able to recover the stolen item, however the information you give us could be the missing piece of a bigger puzzle we have been looking at."
Industry association NSW Farmers said damage to oyster leases were also a significant problem for growers.
Caroline Henry, who has been farming Sydney Rock Oysters at Wonboyn Lake in southern NSW for more than 30 years, said boat users sometimes presumed taking a few oysters wouldn't matter.
"If everyone took a dozen oysters off somebody's lease the oyster farmer would have nothing left to sell," she said.
"It's not just the theft of the oysters, it's when they destroy the infrastructure the oysters are in."
Caju Barbosa, who farms oysters in about 70 hectares of water at Port Stephens in the Hunter region of NSW, said surveillance cameras were helping reduce theft.
He told AAP that thieves were also potentially contaminating rivers with stolen oysters.
"Thieves steal 20 dozen here and 30 dozen there and put them in the water so they can sell them as a big number all at once, and they can bring a disease to an estuary that it didn't have."
