Lionfish are beautiful, colorful reef fish found throughout the Indian and Pacific oceans - that's the good news. The bad news is they're now found all over the Caribbean Sea and the Atlantic coasts of North and South America as well. Alien to those waters, lionfish are the perfect invasive species - aggressive, without predators, prolific breeders and tolerant of a wide range of conditions. Numbering in the millions, they are damaging to native fish species. Diving in the Bahamas to help clear lionfish from reefs, sitting down to a lionfish dinner in the Yucatan and joining a lionfish-only fishing derby in Florida, Carl Safina learns how people are fighting back.