Lurking in the waters of the Atlantic Ocean is an unwelcome predator. The lionfish is an invader, and it is far from its home on coral reefs in the Indo-Pacific basin. The mystery of how they got here has slowly unraveled. A showy species for personal aquariums, they were likely dumped off the Florida coast when no longer wanted. Several small releases of lionfish have led to a population explosion that has increased 1,000 percent in less than 5 years.