Being utterly nitpicky about this; the lionfish can now be listed as "Western Atlantic" (Carolinas to Florida, IIRC), too.
It seems some fools decided they couldn't handle the fish and, rather than kill the fish, tossed them in the Atlantic.
Maybe this was with the best of intentions but it turns out the lionfish are reproducing and have no apparent preditors in the Atlantic.
NOAA is tracking these fish and want reports of sightings from divers.