King of the Reef? Not So Fast, Lionfish

Lionfish
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Stephen Broadbelt remembers when he first spotted lionfish (Pterois volitans) in the waters off Grand Cayman. It was in January 2008, some 20 years after it is estimated that these beautiful but venomous fish — native to the Indo-Pacific — were accidentally introduced to the Atlantic and Caribbean, probably in the 1980s.

That wasn't the first time aquarium fish had been released into the ocean, but the lionfish is the only invasive species known to have survived and thrived in the Caribbean. Broadbelt, who co-owns Ocean Frontiers, a dive operation on Grand Cayman’s East End, says if you had asked any marine biologist 20 years ago if such a thing were possible, the response would have been a resounding “No way.”

“That would have required a male and a female to both survive and to find each other in the open ocean and to choose to spawn and reproduce again and again," he says. "So for the lionfish to be able to do this shows how strong they are at establishing themselves in a reef ecosystem."

Marine Invasion

But what might seem like a happy ending for the lionfish has been a catastrophe for the reef system. The spiny and aggressive piscivores grow quickly and reach sexual maturity early and then reproduce in large numbers, allowing them to outcompete other fish of their size on the reef on all levels. They eat reef-grazers such as parrotfish and damselfish, with the result that those fish aren’t around to keep the reef free of algae. When algae take over, they smother the corals and kill the reef.

The effect of lionfish predation was first seen in the Bahamas, where fish diversity plummeted after the arrival of the lionfish. Then the lionfish rode ocean currents to new territory and can now be found at other islands in the Caribbean, all the way to Belize and Honduras in Central America. And their presence is taking a toll. In some Atlantic locations, the voracious predators have wiped out 95 percent of native fish.

Stephen A. Smith, DVM, Ph.D., is a professor of aquatic medicine/fish health and wildlife and exotic animal medicine at Virginia-Maryland Regional College of Veterinary Medicine in Blacksburg, Va. He’s an avid scuba diver whose travels have taken him throughout the Caribbean. In the past three years, he has seen a significant increase in lionfish populations.

“The biggest change I have seen is the dramatic and alarming decrease in native fish species, along with the dramatic increase in lionfish numbers,” he says. “Lionfish are top-of-the-line carnivores and eat everything and anything they can catch. As lionfish are not native to the Caribbean, they do not have any natural predators, so their numbers go unchecked.”

Pamela J. Schofield, Ph.D., a research fishery biologist with the United States Geological Survey, would not have predicted the possibility of lionfish establishing and spreading so widely and worries that more fish will follow. She wonders if it’s a symptom of increasing global trade, noting that more than 30 species of non-native marine fish have been found off the coast of Florida alone.

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