Lionfish Discovered along the South Atlantic Coast: A Curiosity … or a Wake up Call?
Local divers off the coast of North Carolina were not expecting to see what they found on that August day in 2002: exotic and beautiful lionfish, common to the warm waters of the western Pacific but non-native and unknown off the Carolina coast.
A year later, scientists from NOAA’s National Centers for Coastal Ocean Science had documented 19 different lionfish sightings at eight different locations along the North Carolina shelf. And lionfish by then were being documented also off Florida, Georgia, and South Carolina, with juvenile lionfish showing up off Bermuda and as far north as Long Island, N.Y.
A NOAA press release and the scientists’ publication of a peer-reviewed article on their discovery led over time to divers’ reporting still more sightings of the distinctive fish, far from its natural home.
Taken together, these observations demonstrated that lionfish adults, apparently for the first time, were established and distributed along the U.S. continental shelf from south Florida to Cape Hatteras, N.C. NOAA Scientist Paula Whitfield says that finding represents the first successful introduction of a marine fish from the western Pacific to Atlantic coastal waters of the United States.
Pterois volitans and Pterois miles*, commonly called lionfish, are popular salt-water aquarium fish with distinctive maroon and white stripes, fleshy tentacles above the eyes and below the mouth, and an imposing fan of prickly venomous spines with a poison that can cause severe pain, numbness, and paralysis.
Today, home aquarists are most often experiencing stung by their pet lionfish, but, divers could be more be at risk if lionfish increase in numbers along the heavily populated eastern seaboard.
Lionfish prey on a wide variety of smaller fishes, shrimps and crabs, and they have few reported predators in their native range, where they occupy the upper levels of the food chain. At present, little is known about how other reef species in the lionfish’s “adopted” environment might fare against them.
Since the first sightings in the mid-1990s, adult lionfish have been observed and positively identified in increasing numbers in the Atlantic Ocean off the east coast of the U.S. stretching from south Florida to North Carolina. Juvenile lionfish have been sighted as far north as Long Island, New York, though it is likely that cold winter season water temperatures prevent adults from surviving the change of seasons.
The number of observations and the considerable geographic distances between sightings suggest that more lionfish exist along the Atlantic coast from Florida to Cape Hatteras, N.C., including Bermuda. That same information also suggests that lionfish have been able to survive winter water temperatures off the southeastern coastline. Survival of lionfish is believed to be possible off Bermuda but unlikely on the shelf north of Cape Hatteras because of the colder winter temperatures. Sightings of juveniles that are smaller than is typically available in the aquarium trade suggested successful spawning by the introduced fish, but there are no known observations of lionfish spawning along the east coast.
Non-native marine fish introductions are unusual. Generally, they have not been widely perceived as posing a significant threat to marine ecosystems. Research on the effects of invasive marine fish species on marine ecosystems, however, has been minimal, providing scant basis for authoritatively addressing questions such as: Is this new discovery a cause for concern? Should something be done about it? If so, what?
Lionfish introduction irreversible, NOAA research team concludes
This past summer, NOAA researchers Jonathan A. Hare and Paula E. Whitfield, from the National Centers for Coastal and Ocean Science completed An Integrated Assessment of the Introduction of Lionfish (Pterois volitans) to the Western Atlantic Ocean. The first integrated assessment to be conducted by NCCOS scientists, their report begins to address these questions from an overall perspective.
The intent of this and other NCCOS Integrated Assessments is to pull together research results to assess what is known, forecast future ecosystem impacts, and provide information managers can use to develop options for future action.
Hare and Whitfield conclude that introduction of lionfish to U.S. waters is very likely irreversible. They say large-scale attempts to remove already-present lionfish from the western Atlantic Ocean appears impractical and unlikely to be cost-effective. Lionfish are now distributed along the entire southeast coast at depths between 80 and 250 ft, they point out, making complete eradication all but impossible. Placing a “bounty” as an incentive would likely only lead to increased interaction between lionfish and the public, and increase the risk and frequency of painful stings.
Hare and Whitfield conclude that lionfish will increase in abundance, their presence in the southeast United States continental shelf will become more noticeable, and inevitable, people/lionfish encounters will lead to painful and annoying stings. Because most observations off the U.S. coast to date have been at depths of 100 ft. or more, SCUBA divers are the most likely to encounter lionfish, but they caution that lionfish will also be caught by recreational and commercial fishermen.
In An Integrated Assessment of the Introduction of Lionfish (Pterois volitans) to the Western Atlantic Ocean, Hare and Whitfield also examined existing and potential impacts of lionfish on marine ecosystems, and, more generally, potential threats posed by marine invasive fish species. They examined successes and lessons learned from management actions, such as voluntary guidance to cargo ships for ballast water exchange and actions taken by Bermuda, Hawaii, and Maryland to limit imports of problematic fish species. They concluded that action is necessary, and that management actions can decrease the risk from marine fish invasions.
Evidence points to the aquarium trade as the point of entry
Hare and Whitfield in their Integrated Assessment report that the aquarium trade appears most likely to be responsible for the introduction of lionfish into the U.S. waters.
They cite recent research conducted by the Reef Environmental Education Foundation that reports a number of other aquarium fish are currently surviving off the coast of Florida. Moreover, color patterns of those lionfish identified off the southeastern United States are similar to those from the Philippines, the source of many of the lionfish collected for the aquarium trade.
The scientists point out that an unintentional release from an aquarium did occur in 1992, but they say it is impossible to determine if these fish account for those now being identified off the eastern seaboard.
The specific manner of lionfish introduction into the western Atlantic Ocean remains something of a mystery. Home aquarists could have released lionfish once they became too large for their aquariums or for other reasons, Hare and Whitfield note. There is no evidence to suggest that ballast water is a source for the lionfish invasion although it is a common source of many marine invertebrate introductions. Further, although lionfish have been introduced into the western Mediterranean, likely through the Suez Canal, no evidence suggests that they crossed the Atlantic nor that they entered the Atlantic through the Panama Canal.
Ecological impact, now minimal, linked to lionfish population growth
For now, reef communities in the Western Atlantic Ocean are unlikely to be adversely affected by the debut of the lionfish, Hare and Whitfield explain, because the lionfish are still relatively few in number.
But they say substantial growth in the lionfish population may lead to increased ecological risks and damages. Lionfish could pose concerns for native ecosystems through predatory interactions with native species, they caution. In addition, other stress factors are already causing these ecosystems to undergo changes likely to favor continued growth and dispersal of the lionfish population.
Lionfish ambush their prey by using their outstretched fan-like pectoral fins to slowly pursue, and “corner,” their prey, (lionfish don’t sting their prey, but their spines are thought to be more defensive in nature.) Overall, the scientists point out, predatory interactions of lionfish within reef communities are not well understood. The are concerned, however, that lionfish could decrease prey population abundance and/or compete with other predators.
Another factor considered in their report: Native prey species’ lack of experience in confronting the intimidating lionfish may actually heighten the lionfishes’ predatory efficiency.
One more unknown piece of the lionfish puzzle: few potential lionfish predators are believed to exist even in their native ranges, let alone in their new neighborhoods. Questions abound on what a predator in the Atlantic Ocean will make of this “new kid on the block.”
Other stress factors – ranging from impacts of overfishing to risks posed by climate change, and all of them acting in combination – may further benefit the lionfish’s already impressive competitive advantages, potentially allowing it to extend its range further northward.
Many potentially important reef fish predators that otherwise might compete with lionfish are already reported to be overfished, Hare and Whitfield remind us. Also, the tropical reef fish fauna of the southeast United States already appear to be extending their range northward, possibly because of warming ocean temperatures. Other NOAA researchers have found that from the 1970s to the 1990s, both the number of tropical species and the abundance of individual tropical species have increased off the coast of North Carolina.
Management actions can decrease risks from marine invasions
Hare and Whitfield examine various control options and identify potentially promising steps in the following five areas:
- tracking of the lionfish population. Although increased sightings in recent years suggest an increase in lionfish numbers, hard conclusions must be drawn with caution because the seeming increase could actually be a function of increased public awareness and reporting, rather than of absolute increased numbers. A statistically valid monitoring program is needed, Hare and Whitfield write, to determine if the number of lionfish is, in fact, increasing.
- research concerning the lionfish population and its ecosystem impacts. Scientists’ ability to predict future lionfish population abundance and the effects of lionfish on the ecosystem is greatly hindered by a lack of knowledge, Hare and Whitfield point out. They say more research is needed to adequately determine the ability of the lionfish population to survive, reproduce, and grow along the southeastern U.S., and they recommend more research to investigate potential effects of the species on the ecosystem.
- increased public outreach and education is critical. They point specifically to lionfish, but also more generally to the harm that can come from intentional or unintentional releases of aquarium species into the environment. In the U.S. and throughout the Caribbean, the public needs to be alerted to the presence of lionfish, and encouraged to report sightings to NCCOS’s Beaufort Laboratory. At the same time, the public needs to be aware of the health risks from potential stings, and cautioned against attempting to handle the fish.Scuba divers and others can help with the NOAA research effort by reporting lionfish sightings to Paula Whitfield, NOAA Beaufort Laboratory; 101 Pivers Island Rd. Beaufort, NC 28516 -9722; phone: (252) 728-8746; fax: (252) 728-8784; email: firstname.lastname@example.org. Please be prepared to provide coordinates of where the lionfish was found and at what depth. If possible, photographs or video should accompany the above information.
- notifying physicians and health care providers of the presence of venomous fish in U.S. waters. Because a majority of lionfish observations on the east coast of the U.S. are from waters more than 100 feet deep, SCUBA divers are most likely to encounter lionfish. One study of reported lionfish stings, mostly involving aquarists, noted no fatalities. Most stings have resulted in uncomplicated wounds with severe local pain that was responsive to immersion therapy. The greater risk appeared to be secondary infection resulting from the wounds. Health effects to divers, however, could be exacerbated by depth in the ocean and by distance to medical facilities. Besides medical personnel and health care providers, boat operators and life guards also need to be advised regarding treatment options.
- carefully crafted regulations to control non-native marine species introductions. Bermuda’s approach, a strict ban on import of live fish, is proving an especially effective way to reduce the risk of aquarium releases. But Hare and Whitfield caution that although additional regulation might reduce risks that non-native marine species are introduced into U.S. waters, the issue is more complex than simply limiting imports of non-native species. To limit effects of marine fish invaders on marine systems in the United States, they say, two issues need to be addressed jointly:
- regulating imports of marine aquarium fish into the U.S.; and
- regulating the collection of aquarium fish in the U.S.
Moreover, they caution, efforts to restrict introductions of marine fish will fail unless natural dispersal of species post-introduction is also considered. This consideration calls for regional management approaches limited not by political boundaries, but by the scale of natural ecological dispersal, the scientists write.
Lionfish successes highlight risks from marine fish introductions generally
The introduction and viability of lionfish along the east coast, Hare and Whitfield conclude, is leading to new perspectives on how marine fish invasions may pose threats to marine ecosystems. They call for expanded research and a cohesive plan to manage, mitigate and minimize effects of marine invasive species on ecosystems already under stress from other human activities.
Lionfish are highly visible, recognizable, and distinctive, they point out. But there are already many invasive invertebrate species and freshwater fish species, some of which are causing real problems. The scientists’ research on lionfish raises potentially troubling questions, with no clear answers: How many other less noticeable invasive marine fish species have established themselves along our coasts without being recognized? And what effects are they having on the nation’s resources?
Continuing research by NCCOS scientists over time will provide coastal managers more insights for weighing such questions.
* DNA studies have been unable to determine if P. volitans and P. miles are two valid species or the same species, with P. miles inhabiting the Indian Ocean and P. volitans the western Pacific. Work is ongoing to resolve this uncertainty, but the Pterois volitans/miles complex is native to the Indian and western Pacific Oceans and only recently moved in along the east coast of the U.S.