Taming the Lionfish: Can Predators Be Trained to Control an Invasive Species?

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Antonio Busiello

Grey reef sharks look on at a lionfish in Roatan, Honduras, March 2011. These sharks are being trained by the Roatan Marine Park to eat the lionfish that are invading their reefs.

In March, on a small reef off the coast of Honduras, a group of pioneering conservationists started teaching sharks how to hunt. A half-dead lionfish, speared earlier by a diver, was released into the midst of a swirling mass of grey reef sharks. Sensing the lionfish's final twitches, the sharks descended on the weakened prey. Unsuspectingly, a second lionfish wandered into the frenzy. Within seconds, it, too, was gone. All that remained was a trail of mush emanating from a shark's toothy maw.

Floating in the nearby blue, photographer Antonio Busiello was there to capture the moment he and members of the Roatan Marine Park, a grassroots community organization in Honduras, had spent three months waiting for. "We weren't sure the sharks would hunt on their own," Busiello recalls from his studio in Los Angeles. Although not yet common behavior, the reef sharks' voluntary hunt brings hope of a new way of battling the long-problematic proliferation of lionfish in the region. The aquarium pet turned invader, with it's voracious appetite, prolific breeding and territorial nature, has locals and scientists up and down the Caribbean and Northern Atlantic worried about the threat it could pose to coastal ecosystems and economies by wiping out the stocks of small fish in an already stressed ecosystem.

As any aquarium enthusiast who unwittingly put their new lionfish in a tank with other prized fish will soon discover, lionfish are not great neighbors. They are indiscriminate hunters: A 2009 study by the U.S. National Oceanic and Atmospheric Administration (NOAA) in the Bahamas shows, lionfish consumed more than 41 species of fish, including commercially valuable species like grouper and snapper as well as fish that keep the reefs clean of algae. They are extremely fecund — female lionfish can release upwards of two million eggs each year — and ferociously territorial, chasing out the original occupants from their newfound turf.

Since the lionfish arrived in Roatan in May 2009, divers and locals have noticed a visible decrease in the number of other juvenile fish. As no studies have been done in the area, they can't be certain it's all because of the lionfish — poaching and overfishing could also be culprits — but they're not taking any chances. It's a similar story across the Northern Atlantic. A 2006 NOAA study found lionfish to be the second most common species in coastal waters from Florida to North Carolina. Unsure of what kind of impact they might have, but with a multi-million dollar fishing industry and local biodiversity at risk, NOAA, the U.S. Geological Survey, the National Invasive Species Council, and even the State Department are keeping tabs on their movement.

The USGS maintains a database of lionfish sightings, mapping where they have established communities, and the governmental bodies are informing transnational actors and the public about their potential impact. The Georgia Aquarium, the world's largest, is currently educating visitors about the problem through a NOAA-sponsored exhibit. As for solutions, one idea born from their efforts is the lionfish hunting derby. In February, the Roatan Marine Park (RMP) organized a three-day extravaganza where participants caught over 1,300 lionfish in local waters. Derbies have become a popular way to try and tackle the lionfish population in the U.S. On derby day off the east coast, hundreds of fish are speared and turned into fluffy battered lionfish and lionfish tacos.

But while there are fewer lionfish about in the days after the mass catch, the events don't appear to make a permanent dent in the problem. This is where the RMP and others hope the sharks will come in. "I've always maintained that sharks are gonna figure this thing out," says Samuel Gruber, a 40-year veteran shark expert at the Bimini biological field station in Florida. In the Indo-Pacific, the native ocean of the lionfish, sharks are known to prey on them with no ill effects to their health, despite the potent neurotoxin in lionfish spines that other species, including humans, can't handle. Though Roatan's sharks haven't fully incorporated them into their diet, Gruber says training the predators will not take as long as some think. In the 1970s, he trained lemon sharks to wink at a flash of light. A form of classical conditioning, he says the experiment shows the speed at which the sharks can learn — about 10 times faster than cats — and though he says he still needs more evidence, it may also demonstrate that sharks can also learn from watching each other.

Taking a cue from Honduras, Gruber plans to teach his lemon sharks at Bimini, where there is also a lionfish problem, to hunt the invasive species too. And, he says, the lemon sharks may even do a better job: "Lemon sharks are really adaptive at sticking their heads under crevices and sucking stuff out down there. They don't grab 'em or bite 'em, they actually suck them."

There are, of course, limitations to this method of controlling a species gone wild. The reef and lemon sharks are non-pelagic, meaning they stick within the few miles that make up their reefs and don't travel far. And even if the sharks do take to eating lionfish, scientists agree it's not possible to exterminate them all. "Eradication is rarely a viable option for most invasive species because they just become too abundant, too quickly," says Al Dove, an invasive species expert and Senior Scientist at the Georgia Aquarium. "Usually resource managers look to control the problem and to help the ecosystem find a new balance where the invader is suppressed and plays a minor role, rather than overwhelming everything else."

This is the hope at Roatan, and so far their efforts seem to be paying off. Divers report the numbers of large lionfish are down in areas where the sharks live, though they are yet to see sharks consistently feed on the lionfish without human intervention. (Gruber points out, however, that for most species of sharks, it's rare for humans to observe shark predation unless they're personally feeding them.) In April, Grazzia Matamoros, the director of Roatan Marine Park, wrote to TIME with more good news: moray eels are also starting to get in on the lionfish action. Perhaps nature herself is taking care of business.