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October 2010    Download the Entire Issue (PDF) Available to the Public Vol. 25, No. 10   RSS Feed for Undercurrent Issues
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Is the Lionfish Really a Threat?

are experts overstating their effect, or is there a tipping point?

from the October, 2010 issue of Undercurrent   Subscribe Now

The Pacific “lionfish invasion” in the Atlantic and Caribbean is doing serious damage. Readers report seeing them at nearly all Caribbean diving venues and in increasing numbers. What does it really mean for this body of water, stretching along the American coast down to Mexico, Belize and Venezuela?

William Alevizon, a retired professor of marine biology, asked that on Undercurrent’s blog this summer. In his post, “The Great Lionfish Threat,” Alevizon questions, “Will lionfish simply turn out to be just another interesting fish for reef divers to watch, or will the entire fish population of the Caribbean eventually be reduced to one single lionfish the size of Aruba, waiting patiently for the next cruise ship to pass by?”

Pacific lionfish were brought to the U.S. via the aquarium trade, and experts believe they were introduced into our waters during Hurricane Andrew in 1992, when a broken beachside aquarium released them into Florida’s Biscayne Bay. In the 18 years since, they’ve been spotted as far north as New York’s Long Island and as far south as Columbia’s Caribbean coast. They can live in warm or cold water, on shallow reefs and in deep water environments. In some coral reefs, they outnumber native species.

While Alevizon agrees the lionfish is undoubtedly here to stay, he thinks viewing lionfish as a threat is overblown at this point. “The scientific basis for these concerns is minimal at best, based upon one or two published short-term studies from small patch reefs in a limited area. How these results might extrapolate to large reef areas throughout the region is purely speculative.”

But right here, right now, are lionfish the future straw that will break the back of the already-ill Caribbean reefs? Is there a tipping point where, with the addition of another season of lionfish egg hatching, the Caribbean is doomed? We put these questions to some marine ecology experts currently studying the lionfish invasion to see what they know as fact, what they can only speculate on, and their thoughts about long-term effects.

“If lionfish populations continue to increase as rapidly as they have in the invaded region, and if their predation continues unabated, we could see dramatic impacts,” Lad Akins, director of operations for REEF, told Undercurrent. “While much of the current research is still unpublished, indications are that lionfish impacts will likely be severe.”

Lionfish prey on a wide variety of fish invertebrates and mollusks, basically any moving organism that will fit into their mouths, up to two-thirds of their body size. “When they invade, they eat the abundant prey first, and then start dieting on other species,” says James Morris, an ecologist with NOAA’s Center for Coastal Fisheries and Habitat Research National Ocean Service in Beaufort, S.C. That includes ornamental species, commercially valuable species and ecologically important species.

And they eat constantly, meaning one or two lionfish could quickly wipe out most, if not all, marine life on a single reef. Mark Hixon, a professor of zoology at Oregon State University, studied small coral reefs in the Bahamas and found that a single lionfish per reef reduced the juvenile fish population by 79 percent in just five weeks. Many species were affected, including herbivorous fish, like parrotfish and surgeonfish, and fish cleaners such as shrimp, which sets the stage for more parasitic fish, coral reefs overwhelmed by seaweed, and ecosystems ruined. One large lionfish was observed eating 20 small fish in a 30-minute period. When attacking another fish, a lionfish uses its large, fan-like fins to herd smaller fish into a corner, and then swallow them in one quick strike. And because of their natural defense mechanisms, they aren’t afraid of most other marine life. “We basically had to abandon some studies we had underway in the Atlantic on population dynamics of coral reef fish, because the lionfish had moved in and started to eat everything,” Hixon said. If that continues, picture deslotate reefs devoid of fish and covered in algae.

Is There a Tipping Point?

Sure, Caribbean reefs could carry on with the number of lionfish swimming around and being fished out right now, but the problem is that lionfish grow and multiply at an alarming rate. Morris says a single female lionfish produces about 2 million eggs a year, and her hatchlings become sexually mature in a year. From REEF’s fish-tagging work in the Bahamas, Akins has found that the fish themselves grow at rates up to .5 millimeters a day, much faster than native comparable species like coney, graysby and hind. “From a single report in 2004 in the Bahamas, there are now densities of more than 200 lionfish per acre in some areas. From the first report in the Florida Keys in 2009, we are now getting reports of divers removing dozens in a single day.”

What about sterilizing lionfish, as scientists have done with mosquitoes to try and eradicate malaria? Akins says it has been considered but there are problems with this. “First, lionfish are pair spawners not aggregate spawners, so the number of sterile lionfish required to be introduced would be staggering. Where would these fish come from? Second, lionfish are very long lived, up into decades, and introducing additional long-lived individuals into the system would only increase the long term-impacts. Successful control through introductions of sterile populations usually involve short-lived, highly-productive organisms.”

In an effort to stop, or at least slow down the fearless invaders, the National Science Foundation recently awarded a three-year, $700,000 grant to Hixon and his team to find out why lionfish are so successful in surviving. He intends to compare lionfish populations in the Pacific and Atlantic oceans to find out why they are rare in their native home but thriving overseas. “Something, a parasite, predator, or disease is limiting them in the Pacific,” he says. If the researchers can discover what that is, they hope to use it to create a similar lionfish attacker over here. Currently, there’s no other effort to create one. A divemaster at Little Cayman Beach Resort has trained groupers hanging around the dive sites to appreciate the taste of lionfish. But lionfish have been offered up to moray eels, sharks and other predators with limited success. “They don’t look like their conventional prey,” says Hixon, and the groupers and shark don’t enjoy the venomous spike that comes after taking a bite.

So the experts say humans are the best hope as the lionfish predator. That’s why NOAA and REEF are leading the efforts to get people to eat lionfish. NOAA recently organized a five-city tasting tour with celebrity chefs as part of a campaign to get lionfish commercialized and served in U.S. restaurants. REEF is coming out with a cookbook by year’s end for people to eat it at home. We wrote last October about a seafood distributor shipping lionfish fillets to upscale East Coast restaurants. Another middleman, Traditional Fisheries, has organized 24 Cancun fishermen to catch lionfish and is talking to fishermen in Belize and farther south.

While chefs like the taste of lionfish, it’s improbable that any serious fishery can develop. Catching lionfish is costly and labor-intensive, plus lionfish are slyer and trickier than most commercial fish when it comes to getting caught. They don’t fall for the hook-and- line approach, and they’re hard to get into fish traps, so the only way to catch them is to literally dive with nets and spears. And while they swim close to shore in some places, lionfish also inhabit deep-water reefs in an endless number of areas that divers don’t visit. “Eating lionfish appears to be a viable strategy in near-shore environments where they’re easily accessible,” says Morris. “Off the East Coast, like North Carolina, it’s less of a viable concept because of the cost of getting to the habitat where lionfish are. But it’s a good control strategy for southern Florida and the Caribbean.“

However, with no big, tested plan to keep the lionfish population from exploding, it unfortunately looks like we’re still heading there. From where we sit, it looks like there is no end in sight for lionfish proliferation and habitat expansion. It doesn’t look like we mere mortals can do much about it. It will take a significant Darwinian tweak to alter the lionfish invasion, and those don’t happen overnight.

- - Vanessa Richardson

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