“Divers are ready. Dive, dive, dive.”
On this signal, researchers disappear from the rear of the R/V Cape Fear several times a day into choppy blue water. They descend 120 to 140 feet in search of lionfish.
The Cape Fear rocks 49 miles off Wilmington near the sunken dredge Porta Allegra — or what divers call the “Lobster Wreck.” With its many ledges, Porta Allegra is a favorite hangout for lionfish.
“I think we are going to find out that they are very prolific,” says Paula Whitfield, marine biologist at the Center for Coastal Fisheries and Habitat Research, a National Oceanic and Atmospheric Administration (NOAA) lab in Beaufort.
Whitfield and her crew carry spears and specimen bags in expectation of a large catch of the invasive creature native to Pacific waters. The scientists lead the first Atlantic study on lionfish, a joint project by NOAA’s National Undersea Research Center (NURC) at the University of North Carolina at Wilmington, and the National Centers of Coastal Ocean Science.
IDENTIFYING A NEW INVASIVE THREAT
Recent newspaper and online headlines sound like sci-fi thrillers. “Waters posing possible health threat.” ‘Toxic lionfish spotted off North Carolina.” “Lionfish could turn up off Delaware Coast.” Although a popular fish for marine aquariums, lionfish released in the Atlantic threaten local ecosystems and pose dangers to divers and fisherman.
The lionfish is the first marine invasive fish known to have established itself in Atlantic waters, according to Whitfield. So far, only Pterois volitans specimens have been identified, but genetic studies continue.
In the meantime, Whitfield says the lionfish is becoming the poster child for marine invasive species, already having been named “invasive species of the month” in June 2004 by the National Invasive Species Council.
‘This fish has everything going for it — it has venomous spines, it eats everything, and to top it off, it has these eggs that free float,” Whitfield says of the fish that has few known predators.
Fleshy tentacles, fanning pectoral fins and elongated dorsal spines protrude from this fish in an exotic array of armor dressed in maroon, red and white warning colors. If lionfish spines are touched by humans, they may cause an extremely painful sting, resulting in swelling and in rare cases paralysis.
Also, the lionfish is near the top of the food chain, at least in its native range. This voracious predator stalks deep waters for shrimp, fish and small crab, wielding expanded pectoral fins strategically to corner prey until one sudden, debilitating bite prepares the meal to be swallowed whole.
To spawn, the lionfish releases a floating “mucous balloon of eggs” that drifts within the water column. In the Atlantic, the eggs and larvae likely are transported by Gulf Stream flow, which disperses the population and exacerbates the lion-fish invasion, according to the National Invasive Species Council.
In addition, the lionfish seems to adapt easily to warm waters across the globe. The native range of the lionfish spans the subtropical and tropical reef waters of the Pacific and Indian oceans, and the Red Sea. Along the East Coast, water temperature appears to be the only factor limiting distribution, Whitfield says.
Divers’ reports indicate that lionfish existed in the early 1990s off the Florida coast — after unsubstantiated reports cited the release of six lionfish during Hurricane Andrew into Biscayne Bay in 1992. However, lionfish were not officially reported in the Atlantic until August 2000, when divers spotted them off North Carolina.
Since then, adult lionfish as long as 17 inches have been observed and caught from Florida to Cape Hatteras, usually on wrecks and natural hardbottom at depths of 85 to 300 feet. In warmer seasons, juvenile lionfish are reported as far north as New York and as far east as Bermuda.
Scientists will never be sure exactly how lionfish were introduced to Atlantic waters. Nevertheless, all evidence points to aquarium release, whether accidental or intentional, as the likely source.
Other common sources of invasive species transportation are considered unlikely. “We really don’t think it’s ballast water,” says Whitfield, who knows of no reports of lionfish in water carried in the hulls of shipping vessels for balance.
SIGHTINGS SPAWN STUDIES
Reports from divers and recreational fishers now help researchers map the current distribution of the lionfish.
Since the summer 2000 sightings, reports of lionfish have probably tripled, says Whitfield, who maintains a Web site that tracks public sightings of the creature.
Also, scientists examining sites proposed for Marine Protected Areas (MPAs) found lionfish in natural hardbottoms and reefs located off South Carolina, North Carolina, Georgia and Florida, according to Andy David, research fishery biologist for the National Marine Fisheries Service.
David encountered 15 lionfish during the course of the NOAA-funded cruise last spring. Relying on ROV equipment provided by NURC at UNC-W, David gathered data beyond normal diving depths — where lionfish are seen in habitats up to 300 feet deep.
“They were seen in each of the five areas which have been proposed by the South Atlantic Fishery Management Council as MPAs,” David says.
Increased lionfish sightings by the public and scientists stress the need to know more about this invasive species. Thus, NOAA is conducting both laboratory and field studies on the lionfish.
Last summer, Whitfield and her team visited 22 different sites within Onslow Bay, ranging from 35 to 100 miles from Masonboro Inlet near the NURC facility.
By increasing understanding of the current status and risk posed by the lionfish invasion, the study is designed to predict the effect of lionfish on native fish communities.
The research goals are threefold: to establish population data for comparison in future studies; to characterize and examine what role lionfish play in their habitat; and to predict the distribution.
“Basically, what niches are they filling in this habitat?” asks Whitfield. These “eco-roles” will be characterized through information gathered about the lionfish diet, its rank in the food chain and its reproductive status.
“We know they are predators. We don’t know exactly what they are preying on,” says Whitfield. “There is very little known about even the most basic life history of lionfish. We’re basically starting from scratch.”
North Carolina is cited as the northern limit for winter populations of lionfish due to the warm Gulf Stream influence. To determine the ultimate distribution, scientists need temperature information from the ocean bottom and knowledge of thermal tolerance of lionfish.
“We really don’t have a lot to compare this particular invasion with,” Whitfield says.
The deep ocean is an open system with a constant flux of organisms. In more closed systems, such as a lake, invasive species can be devastating. “There’s a lot less known about marine invaders in general,” Whitfield says of efforts to determine effects on ocean ecosystems.
The study continues through the winter, with a focus on tagging the lionfish to increase the geographic range of the research being done off North Carolina.
ABOARD THE RESEARCH VESSEL
In the ocean, lionfish are sedentary and easy to approach, even docile, when spear-wielding divers are not aggravating them. “They mind their own business and try to avoid you,” explains Jay Styron, a NURC diver aboard the Cape Fear.
Nevertheless, lionfish are dangerous predators — and stalking them with spears can be unsafe, even for research divers.
When Styron felt a lionfish spine puncture his wrist while bagging his specimens, there wasn’t much he could do.
“Underwater I saw him pumping his hand, and I kept asking him ‘Are you all right? Are you all right?'” Whitfield recalls.
Unlike a jellyfish sting, the pain is deeper, “almost like a muscle bruise,” Styron says. To ease the pain, Styron covered his hand in heated water. “It’s an occupational hazard,” he says. “You just go down with the realization that you might be stung.”
Lionfish stings outside of aquariums are fairly rare, however, and Styron thinks he’s among the first stung by wild lionfish in U.S. Atlantic waters.
Surfacing with the lionfish creates another range of dangers — this time for the lionfish, according to Morgan Bailey, a safety diver with NURC. As divers transport a live lionfish from the high-pressure environment of the ocean bottom to low-pressure surface waters, the fish’s swim bladder expands.
Normally the swim bladder helps a lionfish control buoyancy. But when brought up by divers, the lionfish is incapacitated by the pressure change — reaching the surface resembling a spiny balloon.
“We use the hypodermic syringe to vent their swim bladders,” Bailey says, explaining the decompression process.
After each 30-minute dive, researchers surface with up to 28 lionfish. The NOAA crew has seen lionfish at 19 different sites and has gathered a total of 155 lionfish specimens, more than five times the initial goal for the study.
“We’re starting to wish for less,” says Whitfield, who must dissect the lionfish following each dive, a task often lasting until midnight.
With no capabilities for freezing fish onboard the Cape Fear, researchers must dissect the specimens quickly to preserve gonads and stomach organs.
The simple act of cutting open one lionfish reveals a world of questions that, through future research, will soon render the basic life history of the lionfish in Atlantic waters.
The dissection exposes female gonads, a sac filled with up to 20,000 tiny, pelagic, or free-floating, eggs from a female ready to spawn. “Now we know that they are also spawning off of North Carolina,” says Whitfield, holding the gel-like mass of eggs.
Inside the gut, Whitfield finds three small reef fish that have been swallowed whole — these fish will be identified back at the Center for Coastal Fisheries and Habitat Research in Beaufort.
“Their bellies are full of fish, and they have a lot of meat on their bones, so they’re healthy,” Whitfield explains.
EVALUATING ECOLOGICAL IMPACTS
The sheer numbers of lionfish found, and the fact that juvenile and egg-bearing lionfish are among the samples, indicates eradication may be impossible. If further studies by Whitfield locate wintering populations of lionfish, “thoughts of eradication should be replaced by serious management consideration,” according to an assessment by the NURC crew.
“They’re more prevalent than expected, and they’re here to stay,” says Doug Kesling, mission coordinator with NURC in Wilmington.
Species of high commercial value, such as snapper and grouper, may be at risk as lionfish feed on the same food sources and compete for the same habitat. Also, lionfish could prey on the young of important commercial fish that use “live bottom” reefs as nursery grounds, NOAA reports.
As Whitfield and her crew gather wild specimens in the field, NOAA researchers back in Beaufort are developing techniques to successfully spawn and rear lionfish in the laboratory.
Supplied with a fresh batch of Whitfield’s wild-caught lionfish, researchers perform cutting-edge laboratory studies on the reproductive biology of lionfish.
James Morris, biologist with NOAA and doctoral student at North Carolina State University, is developing a model to forecast potential lionfish population growth in Atlantic waters.
Morris is studying both captive and wild-caught lionfish to establish basic information on lionfish reproduction, such as estimates of the number of eggs a female lionfish produces.
“These experiments have given us insight into the reproductive strategy of lionfish. This is new information that has never been documented before,” says Morris.
Morris also is conducting feeding experiments to determine if there are any potential lionfish predators in the western Atlantic. ‘This question is important as the many factors that limit population growth are relatively unknown for lionfish,” Morris says. Experiments also will help scientists find out what exactly the lionfish prefers to eat.
By forecasting the rate of population growth over time, scientists can assess the ecological impact of the lionfish invasion.
The data gathered by NOAA researchers will eventually help answer pressing questions about how lionfish interact with other fish species, like snapper and grouper.
For now, “What we see in the lab will definitely supplement what we see in the field,” says Morris.
This article was published in the Holiday 2004 issue of Coastwatch.
For contact information and reprint requests, visit ncseagrant.ncsu.edu/coastwatch/contact/.
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