This is from the Fisheries:
Freshwater
You must not alter the length of a fish which is subject to a minimum or maximum size limit whilst you are in on or adjacent to any waters in any manner other than by gutting, gilling and scaling. You cannot remove the head or tail. This means you can cannot fillet your fish or possess filleted fish unless you are well away from the water. This rule does not apply if the fish are being prepared for immediate consumption, are being prepared for immediate use as bait, if the fish are being cleaned at a fish cleaning facility or a fish cleaning table at a boat ramp, or for fish that do not have a legal length.
Saltwater
You are not permitted to alter the length of a fish or invertebrate by filleting/ shucking and/ or removing the head/ shell until well away from the water. This rule does not apply at areas normally used for cleaning fish such as boat ramp cleaning tables, if the fish are for immediate consumption or immediate use as bait, or for fish that do not have a legal length. You may clean fish by gilling and gutting only.
Cheers
Hodgey