Well, just the point of messing with animals, that "won't be released into nature", and then are for whatever reason, and change things. In Florida, we have native green anoles, Anolis carolinensis, that have been almost completely run out and bred out by introduced brown anoles, Anolis sagrei. Not exactly pet related, but anytime you play with animals, you risk messing up natural ecosystems. In Australia, you can't import or export anything. Which rather bums me personally, as I have a real fondness for allot of the native Australian reptiles, but they have had enough just from the camels and cane toads. You can actually receive a prison sentence if you are found with a corn snake. It is extreme, but they don't want anything screwing with the unique ecology there and all of the unique species. And here in Florida as well, there have been studies that have shown during the spring, the introduced Nile monitors, Varanus niloticus, are using green iguana eggs, Iguana iguana, as a primary food source. So we now have non-native species using other non-native species as a primary food source certain times of the year. Obviously a bit far from genetic engineering, but the same principle applies. If that deformity in the parrot fish goes along with the mutation, and it is inheritable, and a group of these got into the wild population, then, who knows?