ISLAMORADA, Florida — Almost motionless by the reef, it looks like a dragon guarding an enchanted forest. But its diaphanous, dramatic beauty obscures its deadly nature.

Lionfish, a non-native species and a popular aquarium fish, presents a serious threat to other marine life. With a venomous spine and few natural predators, lionfish are taking over the oceans, destroying coral reefs and fish populations in their path.

"The problem is not just that they don’t belong here," says Lad Akins, director of special projects at the Reef Environmental Education Foundation. "The problem is, what they’re going to do to our native ecosystem."

Lionfish, a species native to the Indo-Pacific Ocean, are suspected to have been released into the Atlantic in the mid-1980s by hobbyists who dumped their aquariums into the ocean.

They have since spread throughout the entire Caribbean and western Atlantic, voraciously feeding on other species that have no natural defenses against the foreign fish.

A group of divers, however, are taking on the fish, trying to curtail its spread by killing it off during individual hunts or competitions such as the Islamorada Lionfish Derby.