Bustaonenut,
I've flown up to mackay to go fishing with mates, and brought fish home no worries.
So long as they're iced down, frozen, packed up properly & securely in the esky, i didn't have a drama at all. Virgin Blue was fine about then. The esky just went in as part of the bulk luggage.
Coming back from Solomon Islands was totally different tho, as we had to go through immigration, had to make sure we had all the correct papers. Worse thing was tho, not allowed to have the skins on, so i'm sure as anything we brought back barracuda instead of wahoo and others we caught over there.
I'd have no dramas flying to mackay again and bring fish back. If you were concerned, give them a ring. I rang them a while ago to find out rod tube max lengths, they couldn't of helped me more than what they did. Fantastic service.
Mark