South Coast fishers have been warned to think twice about abalone theft after a man was sentenced to 12 months jail.

Several sentences have been handed down to abalone offenders in recent weeks.

Department of Primary Industries' Glenn Tritton said a repeat unlicensed abalone offender was sentenced to 12 months behind bars and received fines and court costs totalling $16,900.

“The man pleaded guilty to trafficking in abalone, possessing shucked abalone and obstructing a fisheries officer,” Mr Tritton said.

“When approached by fisheries officers he attempted to escape and was apprehended in possession of 75 shucked abalone."

Mr Tritton said a commerical diver pleaded guilty to six abalone offences, including possessing 27 prohibited size abalone and failing to complete abalone logbooks.

He received fines and court costs totalling more than $18,000.

Operation Maxima, a blitz on abalone fisheries crime, began this month with fisheries officers and police scouring the coast for illegal abalone diving.

"These cases should be ringing alarm bells in the minds of anybody considering illegally diving for abalone," Mr Tritton said.