As for how they got there, I heard at one time something about Hurricane Andrew was it and some big display tanks that broke maybe at private residence maybe at Bay of Biscayne or somesuch?   I don't think the ballast transport theory would work for larval fish; jellies, zebra mussels, OK; predatory fish?  Probably not.  
It was one of my first fish a few decades ago, love 'em, very cool animal.  Where they belong.  When I think of non-native introduced things I think of German Cockroaches,
Norway or other non-native rats, House Mouse, fire ants, feral hogs and cats, West Nile Virus, kudzu and a hundred other plants, Starlings, House Sparrows, and I could go on and on......   These things never turn out well.  No natural predators is a problem.  They inevetably upset if not destroy the balance of nature.  The cat is out of the bag.
Hope they get popular fried.
birdfish