Verifiably Venomous

There are a couple of reasons why lionfish are able to thrive in US waters.

Invasive lionfish don't have any natural predators. Those were either left at home, or maybe lionfish have managed to scare away potential predators with their venomous spines. Check out this diagram of the lionfish features:

http://www.lionfishhunters.org/Lionfish.html











I wouldn't want to come across this little guy while swimming in the ocean, though their sting is not fatal to humans (but it sure is painful). Lionfish are a real threat to native coral reef species, which would ultimately disrupt coral reef processes and biodiversity.

Source:
Hare, Jonathan A. and Whitfield, Paula E. (2003) An Integrated Assessment of the Introduction of Lionfish (Pterois volitans/miles complex) to the Western Atlantic Ocean. Beaufort, NC, NOAA/National Ocean Service/National Centers for Coastal Ocean Science/Center for Coastal Fisheries and Habitat Research, (NOAA Technical Memorandum NOS NCCOS, 2)