The lionfish is an invasive species that is currently wreaking havoc in the warm waters of the Bahamas, the Caribbean, and the US southwestern Atlantic and Gulf of Mexico coasts. But where did they come from and what makes this normally docile hunter suddenly turn vicious in its new home? To answer these questions, North Carolina State University initiated a study of lionfish genetics to learn more about their origins and how to control them.

According to the National Oceanic and Atmospheric Administration (NOAA), over a million red lionfish (Pterois volitans) infest American waters. A native of the Indo-Pacific region, it was unknown in American waters until the 1980s when they began to appear and spread in large numbers. Early DNA analysis indicated that all of the invaders were descended from only a few individuals, suggesting that the fish were the result of a few private collectors dumping their aquaria into the sea.

However, the lionfish is anything but benign – at least, in the Americas. In its normal Pacific habitat, it's a placid creature that hunts and is hunted, but the invading fish have both a voracious appetite (not to mention venomous spines) and can lay 30,000 eggs every five days that quickly scatter on the sea currents. Worse, the lionfish will gorge itself with enormous quantities of prey, but has no natural enemies in its invaded waters. It's also so alien that the native fish ignore it until it eats them.

To combat the lionfish, governments in the region actively support fishing by scuba divers and restaurants are encouraged to place the delicious predators on their menus. Unfortunately, the fish often live in areas too deep or too remote for divers, and they ignore traps, so there have been recent efforts to hunt them down using autonomous robots.

But the question remains, where exactly did the lionfish come from and why is it so formidable in its invasive form? To learn more, North Carolina graduate and undergraduate students were tasked with making genetic comparisons of two native lionfish regions in the Pacific and five invading regions in the Atlantic.

By looking at sequenced samples from two mitochondrial DNA genes, the researchers demonstrated that the best match was between the lionfish in the Bahamas and those in the waters around Taiwan – indicating that the latter is the source of the invaders.

Since a species introduced into a rich, virgin environment tends to undergo rapid mutation, the team also looked to see if the invading lionfish were a hybrid of two other lionfish species, such as of red lionfish and the common lionfish, also known as the devil firefish (Pterois miles). No evidence was found, but the possibility has not been ruled out.

But one other question remains: can genetics help in controlling the invading lionfish? That still remains to be seen.

"Some of these invaders rapidly adapt to new surroundings," says Martha Burford Reiskind, research assistant professor of applied ecology at NC State. "What are the genes that allow them to successfully invade? Can we make better predictions so that invasive species like P. volitans are eradicated before it's too late?"

The research was published in Biological Invasions.