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The lionfish invasion: A call to arms?

  • First reported off the Florida coast in the 1980s, lionfish have now been spotted off coasts from New York to Brazil.
  • With an indiscriminate appetite – more than 70 species of fish and invertebrates have been picked out of lionfish stomachs – the extravagantly striped invader is scarfing up so many fish that prey may become less available for native species.
  • Innovators and marine managers are hoping that technology can turn the tide against lionfish.

A battle is brewing in southeastern U.S. waters, the Gulf of Mexico, and the Caribbean Sea: it’s the lionfish against all comers. With voracious appetites and virtually no predators, these invasive fish are damaging reefs and fisheries. Oblivious to their enemy status, the lionfish are winning this war — for now.

The quest to remove this unwelcome guest is spawning inventions that range from underwater robots to fish traps armed with special recognition software. While testing for these devices is still underway, the innovators and marine managers are hoping that technology can turn the tide against lionfish.

“It’s the inverse of every fisheries management plan you’ve ever heard of,” says Corey Eddy, a marine biologist who studies lionfish around Bermuda. “Usually we’re trying to minimize the pressure on fish populations so they can rebound. Now we’re saying, let’s start wiping them out.”

Lionfish have become one more name on the lengthening list of invasive species. Native to the Indo-Pacific, experts believe the problem started when these ornamental fish from the aquarium trade were set free in U.S. waters and then made themselves too much at home. First reported off the Florida coast in the 1980s, lionfish have now been spotted off coasts from New York to Brazil.

With an indiscriminate appetite — more than 70 species of fish and invertebrates have been picked out of lionfish stomachs — the extravagantly striped invader is scarfing up so many fish that prey may become less available for native species. The lionfish also gobble up the grazers, such as wrasses and tangs, that clean algae off the reefs. So far, bigger fish haven’t developed a taste for the pushy newcomer, leaving the lionfish to gorge and reproduce unchecked.

An invasive red lionfish (Pterois volitans) waits to be hauled to the surface, where it will eventually be used by NOAA to conduct lab studies on lionfish reproductive biology, age, and growth. Photo by Karen Doody, courtesy of U.S. Geological Survey.

To deal with the overabundance of lionfish, management plans rely on spearfishing tournaments, special lionfish culling permits, and incentives, such as offering coveted permits for taking other fish when a premium number of lionfish are killed. On a good day, a single spearfisher might bag hundreds of lionfish, but that number can’t begin to keep pace with the two million eggs a female lionfish could spawn every year. And the lionfish aren’t always swimming in shallow waters where spearfishers usually hunt. Scientists have found large groups of lionfish lurking below 130 feet, too deep for the typical recreational diver.

While the fish have steadily gained new underwater grounds, until recently researchers knew relatively little about their basic biology, says Eddy, who just published a study describing the feeding habits of lionfish around Bermuda. “These fish are such successful invaders, the more we understand about them, the better we can target them and get as many out of the water as we can,” he notes.

Robots to the rescue

If humans can’t control lionfish, perhaps robots can. During a dive trip to Bermuda, that’s the thought that crossed the mind of Colin Angle, cofounder of iRobot. After all, his company successfully builds autonomous devices that clean up everything from the dirt in people’s homes (the Roomba) to radioactive waste in nuclear power plants. Why couldn’t a robot clean up lionfish?

To tackle the problem, Angle and his wife, biochemist Erika Ebbel, started Robots in Service of the Environment (RISE). With an all-volunteer crew of engineers, entrepreneurs, and scientists, the nonprofit is developing an underwater robot that jolts lionfish with a lethal electric current.

The three-by-two-foot prototype weighs about 30 pounds and has three main components: a remotely operated underwater vehicle (ROV), a pair of paddles to deliver the electric current, and a control system. The idea is to use a laptop or iPad to drive the ROV over a fish, press a button to zap it, then capture the fish in a tube, says John Rizzi, executive director of RISE. Eventually, the device would become increasingly autonomous.

RISE is working on a remote operated vehicle (ROV) that could target the lionfish. The prototype would use a robot arm with two metal electrodes on the end to electrocute invasive lionfish. The stunned fish would then be collected in a central chamber. “The lionfish exist at all levels in the ocean, our goal is go after the fish that divers can’t get to,” says Rizzi. Photo courtesy of RISE.
Testing part of the prototype for the robotic lionfish zapper. Photo courtesy of RISE.

The components have already been tested in a tank and they hope to have an ocean-going version by early next year. The biggest challenge? The ocean itself, says Rizzi. “It’s a tough environment. You have to deal with salt water, changing temperatures and pressures. And there’s no remote communication under water with radio, so the setup has to be wired or completely autonomous,” he says.

It’s not yet clear how many lionfish could be killed during each outing, nor can they estimate an off-the-rack price for the robot. The goal, however, is to build an affordable commercial version.

“Ultimately the way this becomes a success is by creating a market and the interest of consumers in eating lionfish,” says Rizzi. “The best way to challenge the sustainability of a species is for humans to eat it. Whether that’s good or bad, in this case that will benefit the environment.”

And there’s more than one way to kill a lionfish.

Deadly force

After watching the colorful lionfish accumulate around the Gulf Coast reefs where they dive, Bryan Clark and his wife Anna were also inspired to start a nonprofit environmental organization, Coast Watch Alliance. Although the Alliance works to protect reefs in general, battling the lionfish occupies much of their attention.

In his so-called “lionfish weapons lab,” the first device Clark made looks like a leaf blowing machine. With a high-capacity water pump in the backpack, he planned to slurp up lionfish, one after the other, or attach the device to an ROV. Then it turned out that lionfish flee while the suction slowly ramps up. So, he’s working on the next prototype, which will operate more like a lionfish does — taking its prey with one sudden, powerful gulp.

However, Clark’s main focus is on developing a “hunting ROV” with a camera to scout reefs for lionfish before making a dive. Eventually, he wants to rig the ROV with the vacuum or another one of his inventions. For example, it could carry the pneumatic spear gun he designed, which is powered by the CO2 tank from a paintball gun.

One drawback to the ROV is the lack of fine motor movement capability, which makes pinpoint accuracy difficult, notes Clark. To overcome that, he envisions configuring an ROV with a series of highly maneuverable small mirrors that can direct laser beams to target the fish and then mortally wound them. That’s a little more “Star Wars-y” and may take a few more years to get right, he says.

Overall, Clark believes a combination of technology and incentives will take down the lionfish. “Some people are going to harvest lionfish because it’s great for the environment, others will do it because it’s fun to do while they’re diving. But a lot of people are going to do it because they’re going to make some money taking lionfish to the market,” he says.

One way to clean up lionfish: Bryan Clark’s vacuum backpack. Courtesy of Bryan Clark.
The prototype for Clark’s “hunting ROV.” Photo courtesy of Bryan Clark/Coast Watch Alliance.

Fatal At-trap-tion

One commercial market that lionfish have unwittingly entered on their own is the spiny lobster fishery. Although lobster traps weren’t designed for lionfish, one study showed that about 20 percent of such traps end up with lionfish bycatch.

“lf the lionfish are showing up in those traps, uninvited and unintended, then why not get them to show up intentionally?” asks Bob Hickerson, a long-time diver and Florida contractor who is using his skills to build a better fish trap. When it’s finished, the “Frapper Trap” will use a pattern recognition program to capture lionfish, yet allow other aquatic species to swim away. His team includes his wife, Maria, a diving instructor, and his father-in-law, retired physicist Gonzalo de la Peña Casares, as well as volunteers from Team Frapper — a name derived from a French word that means “to strike down.”

In the first phase, they designed an under water structure that lionfish would gravitate toward, called a Fish Attraction Device (FAD). With the help of Smithsonian Institute researchers, two of these models were deployed in deep waters off Curaçao, an island near the coast of Venezuela.

Phase Two is now taking place inside a big yellow tank, set up in the courtyard of Hickerson’s house. Here, he’ll test whether lionfish are bothered by the movement of a manual gate on the trap. The idea is to contain fish in a foyer where a camera can collect images of whatever species swam in. With de la Peña Casares‘ recognition program, if lionfish are detected, then a gate opens into the trap. Other fish won’t trigger the inner gate, so they can simply leave.

How many lionfish can a Frapper trap trap? Although the working model would easily hold 50 fish, no one knows if the fish would tolerate that density. “We know they like to get close to each other, we just don’t know if 20 lionfish are already in there, would another want to come in?” says Hickerson.

He’s hoping to have a submersible trap ready to test within the next six months. “We can’t stand back and watch our reefs being taken over by lionfish,” Hickerson says of these efforts.

The fish attracting device (FAD) designed by Team Frapper and deployed off the coast of Curaçao. Photo by Substation Curaçao, courtesy of Bob Hickerson.

The idea of using image recognition traps also occurred to a team of engineers who have never donned dive gear. When NOAA put out a call for a trap that wouldn’t catch anything but lionfish or contribute to ghost fishing, they thought a solution was in their wheelhouse.

“We knew little about deploying things underwater or the behavior of fish, but we’re really good at developing low power, low cost sensors,” says Brent Roeder of R3 Digital Sciences in Virginia.

His team conceived of an “extension kit” that would add recognition capabilities to the traps already built to catch spiny lobsters. The lionfish have such a unique profile, notes Roeder, that you don’t have to do too much to develop recognition: “Imagine tracing the outline of a lionfish. It has all these spines hanging off. Other fish don’t look like that.” Of greater concern was that lionfish might be scared away by the lights needed for the image system. Without lights, the traps wouldn’t work in the darker depths.

While Phase One results using an underwater data collection system showed their extension kit was viable, the call for Phase Two was only recently posted. If they get a chance to move forward, Roeder says the ultimate goal would be to sell large quantities: “If there are hundreds of thousands of lobster traps in Florida, then we’d want to sell these at least in the tens of thousands — for around the same $30 cost of the spiny lobster traps.”

Low tech too

There might even be a good way to catch lionfish without any fancy trappings.

“More than any other fish I’ve seen, lionfish are attracted to structures,” says Stephen Gittings, science coordinator at National Oceanic and Atmospheric Administration Office of National Marine Sanctuaries. “You could throw an office chair in the water and they’d come over.”

With that in mind, Gittings has been tinkering with several versions of a simple net trap spread under a FAD. He started with a bulky PVC frame, a bucket, and a curtain of netting that laid on the ocean floor until the whole contraptions was pulled up to the surface.

After testing prototypes off the Pensacola coast in Florida, Gittings found they were good at attracting lionfish and counted only one stray bycatch. Soon he started making new models with netting attached to hoops of stainless steel that lay on the bottom and lift up “like two handles on a picnic basket.” Before long he’ll have another version that will latch closed when it lifts. When the nets are pulled up, lionfish don’t scatter the way other fish do, but they could float away as they slowly rise.

There’s still much to learn. How long, for example, should the traps “soak” to capture the most fish before they get pulled?

“I feel like my role in this whole lionfish war is to see if the concept of a FAD-based non-containment curtain trap works,” says Gittings. “Then fishermen can refine it and make it more friendly for their own use.”

Whichever devices become the weapons of choice against lionfish, most experts say that total eradication is unlikely. However, building a strong commercial market for the invasive whitefish could keep the populations from toppling entire ecosystems.

“I think commercial incentive will be a big part of the solution, supplemented by spearfishing in shallow water and some of these other things,” says Gittings. “Some of these might sound like crazy ideas, but you never know until you try.”

Juvenile lionfish. The adult fish can grow up to 18 inches long and live an average of 16 years. Photo by James Morris, courtesy of Beaufort NOAA.
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