A multi-agency flying squad will target illegal seafood sales in the Hunter over the Christmas-New Year period.
Officers attached to Operation Trident, a joint project between NSW Department of Primary Industries, the NSW Food Authority and NSW Police, will conduct overt and covert patrols in coming weeks.
"The Christmas and New Year holiday period is always the peak season for seafood and oyster consumption, which also leads to a rise in illegal seafood trading, NSW DPI director general of fisheries Sean Sloan said.
"We are working with NSW Police and the NSW Food Authority to ensure that the seafood that lands on NSW plates is safe, lawfully obtained and sustainably harvested."
State rural crime coordinator detective chief inspector Cameron Whiteside said police had seen an increase in oyster thefts in recent weeks.
"We encourage people to report these thefts so we can have timely investigations and put a stop to this activity," he said.
Maximum fines of up to $275,000 and imprisonment apply. Offences cover both the sale and purchase of illegal seafood.
"The black market trade poses a health risk to consumers. We strongly urge the public not to consume seafood products if they do not know where it has come from, NSW Food Authority chief executive Dr Lisa Szabo said.
"Stolen oysters might not come from an area covered by the NSW Shellfish Program, so the NSW Food Authority recommends people only buy oysters from reputable retailers as these oysters have been monitored for their safety by industry professionals."
Illegal or suspected illegal fishing activity can be reported to the Fisher's Watch Phoneline on 1800 043 536. Anyone with information about marine-related crimes should contact Crime Stoppers on 1800 333 000.