Whyalla's Stephen Mark Cook, 47, received a suspended sentence in the Whyalla Magistrates Courts on Thursday after pleading guilty to illegally selling jars of razorfish at a local hotel in October last year.

This comes after Cook appeared in Port Lincoln's Magistrate Courts in late May where he pleaded guilty to a charge of interfering with a lawful fishing activity.

At that court appearance Cook was fined $991 and was disqualified from holding or obtaining a fishing licence.

In relation to his latest court appearance, Primary Industry Resources SA (PIRSA) fisheries officers seized a total of three jars containing 44 razorfish when they approached Cook in the hotel last year.

Officers discovered a further 12 jars containing 296 razorfish in the man's car.

The court was told the man's activities were "neither amateur not spontaneous, but an organised well-planned enterprise to make money".

His honour, Magistrate Clive Kitchin ordered Cook be convicted and sentenced him to three months imprisonment, suspended on entry into a two-year good behaviour bond of $1000.

Magistrate Kitchin also ordered prosecution costs in the amount of $150, court costs, victims of crime levy, forfeiture of all items listed on the complaint and confirmation of forfeiture of the fish.

PIRSA Fisheries Central North regional manager Paul Faithow said the suspended sentence was a strong deterrent to Cook from further reoffending as he faces a prison term if he re-offends in the next two years.

"It sends a very strong message to anyone considering illegally fishing or selling, but also reinforces the message that our fisheries need to be protected, particularly vulnerable species," Mr Faithow said.

There has been so much overfishing of razorfish that the bag limit was reduced to 25 per person in December 2007.

The species is susceptible to over-fishing as it lives in the seabed in the same spot for its whole life.

PIRSA said the species is not migratory and therefore if heavily harvested in an area there would be no new recruitment to enable re-population.

Cook has eight convictions dating back to 1997, including failing to declare his catch, take, possess and sell a protected fish and selling without a licence.

In March 2007 Cook was fined $38,000 for commercial fishing without a licence and had his boat and fishing equipment seized.

Throughout his 12-year history in court, Cook has been fined more than $50,000.