The man contested a $300 penalty infringement notice (PIN) issued by Environmental Protection Agency Marine Parks inspectors for operating a speedboat in a "planing and non-displacement mode" in a turtle and dugong go slow area on January 21, 2007.

He pleaded not guilty to the charge, however, after evidence by EPA marine parks inspectors, was convicted and fined $450, as well as $2500 for court costs.

EPA Moreton Bay Marine Park regional manager Miles Yeates welcomed the court's decision.

"This fine sends a clear message to all boat operators on Moreton Bay that driving at inappropriate speeds through go slow areas will not be tolerated," Mr Yeates said.

"There are currently five go slow areas in Moreton Bay Marine Park created to reduce the number of turtle and dugong deaths and injuries from boat strikes.

"Boats travelling through these areas are not allowed to operate on the plane or in a manner that would reasonably be expected to result in striking a turtle or dugong."

Mr Yeates said boat strike represents a significant threat to the long-term conservation status of these threatened species.

"Turtles and dugong are particularly vulnerable to boat strike due to their tendency to move slowly, and their need to regularly breathe air at the water's surface," he said .

So far this year, the EPA has recorded 46 turtle deaths arising from boat strike in Moreton Bay.