While I think that if we are to regulate a certain species, pick any, say Snapper because they are in decline, then the first point of call should be the restriction of exports (anywhere in Australia). For example, while SEQ may not export Snapper O/S it's pointless supplying the WA market a single fish if they are exporting their snapper (just as an example).
But if the fishery is not in decline, say East Coast King Prawn, then there is no point in restricting exports IMO.