I don't agree that lionfish have known predators. There has never been any routine predation of lionfish by any other species observed anywhere that I'm aware of. The occasional cornetfish or grouper eating one was probably pretty sorry he did. Even parasites seem to leave them alone. You've got some good resources for info on the website - here's another recent study that you might add. Scubadobadoo is right - the only thing that gets 'em is winter.