The NSW Department of Primary Industries inspected a South West Rocks restaurant on May 28, seizing a number of crustaceans after the owner failed to produce documentation showing it had been obtained legally.

Officers took 26 mud crabs, 35 blue swimmer crabs, two coral crabs and two Balmain bugs.

NSW Department of Primary Industries assistant director fisheries compliance Brett Andrew said investigators also interviewed a man they allege may have taken the catch for sale.

"Mud crabs and blue swimmer crabs are quota-managed species and mud crabs are a priority species under the state's fisheries laws, attracting high penalties for contraventions," Mr Andrew said.

"Any activity that could potentially undermine legitimate commercial fishing and compromise the strict quota system is concerning.

"The alleged offenders can expect to receive court attendance notice where they could face a maximum penalty of $110,000 if convicted."

In June, a commercial Port Stephens fisherman faced court charged with illegally using traps to take mud crabs.

"The commercial fisher was under surveillance by fisheries officers and observed using a grapple to retrieve five unmarked crab traps from Tilligerry Creek," Mr Andrew said.

"The court found the commercial fisher guilty of unlawfully using traps for taking fish for sale and fined him $750.

"The court also ordered that he pay the Department's professional costs of $1450."

More than 3400 illegal crab traps have been seized in the past three years. 1103 were taken last financial year.

Mr Andrew said it remained a priority for his officers.

"We'll continue to sustain this effort against illegal crab fishing to protect the resource and ensure it's shared sustainably between legitimate users groups," he said.

Illegal fishing in NSW can be reported on 1800 043 546.