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The Mystery of the
Atlantic Pterois Lionfishes 

by Anthony Calfo

For more than a few years now, people have reported seeing various non-indigenous marine fishes along the Tropical Atlantic coast of the United States of America. In most cases, they have been isolated specimens in isolated locations. In some circumstances, private homeowners would occasionally see ornamental specimens living in their quiet “backwater” canals. Other times, the exotics have been observed lingering around patch reefs, or in lagoons. The source of some of these fishes was suspected to be release from hobbyists or a rare escape of commercially-held specimens from wholesalers of imported fishes during hurricanes or severe storms. But such small numbers of fishes (usually single specimens) cannot form founding populations easily, if at all. And so, the establishment of the Indo-Pacific Pterois Lionfishes in Atlantic waters has been quite a mystery.

To compound the mystery even further, some investigators are inclined to believe that the origin of the founder population of Pterois is on the coast of North Carolina, and not Florida, as most people would expect. At first glance, this is perplexing. To begin with, Florida is the only state in America, outside of Hawai’i, that has a climate even remotely comparable to the Indo-Pacific. Moreover, Florida has an enormous industry of established trade in marine ornamental fishes: both import and export. Florida also has one of the largest state populations and, subsequently, one of the largest bases of participating saltwater hobbyists. These are more likely sources of introduced exotics.

Indo-Pacific lionfishes now appear to be established in the Tropical West Atlantic.  Photo Anthony Calfo

By contrast, however, North Carolina has a rather modest population, and a relatively weak marine hobby market. In fact, they have fewer livestock retailers and hobbyist clubs than most other states in America. The weather, although usually mild, can also be very cold in the winter, and snowfall is recorded. Thus, the statistical likelihood of Pterois establishing along North Carolina coasts seems unlikely compared to Florida. But we must consider all potential sources of a founding population of Lionfishes, beyond the obvious ones stated, before we dismiss or the theory of a North Carolina origin.

By most estimates, there is a reproducing population of Pterois lionfishes in the Western Atlantic. Their population is estimated to be numbering in the thousands. It is not even restricted to the Tropical waters, either! This may sound impossible, but it is interestingly true. The ocean currents shift in summertime with a pattern called the “Gulf Stream” that sends very warm waters from the Tropical West Atlantic north towards New York. Remarkably, species of beautiful Florida and Caribbean fishes can be seen and collected during this time of year along the northern Atlantic coasts.

Joe Yaiullo, Director of the Atlantic Marine World facility, has been collecting “Gulf” species off the coast of New York each summer for many years. I’ve known Joe as a colleague in the aquarium industry for over ten years, and I asked him recently if he’d ever seen Pterois Lionfishes in any of his collections. With an amused smile, he told a story of his first experience with Pterois species in New York waters. He had been asked to do exploratory collections to see if Lionfishes could be found locally. Upon accepting the challenge, Joe reported that within the first 30 minutes of his first collection, he netted a bucket full of juvenile Pterois specimens! He then brought them back to his facility (pers. comm. 2005) where he put them on display for education and public awareness. These specimens were collected merely by wading into shallow water and captured with nets. [note: Atlantis Marine World is a fabulous facility for tourists, aquatic scientists and marine hobbyists alike, which includes an 80,000 liter coral reef display that is magnificent! For more information on the Internet, visit]

Pterois is a formidable predator with patience and persistence.  Photo Anthony Calfo

Sightings of Pterois Lionfishes to date have been reported along most of the Atlantic coast of the USA and from Bermuda in the South to New York in the North. One of the first specimens captured by a fisherman with hook and line was off the coast of North Carolina; the specimen was approximately 43 cm long and over one kilo in weight. Presently, removal of this established exotic fish seems impossible. There have been concerns voiced about public safety, regarding swimmers and divers getting stung by members of this venomous genus, but most experts agree that these are very small risks. No fatalities have been recorded from Pterois envenomation here, and the sightings of specimens at large have mostly been offshore and in deep water (over 20m). The biggest concern overall is the potential reduction or elimination of native species by this non-native predator. While reports of Pterois in the Atlantic have occurred for perhaps ten years or more, very little study has been done to estimate the impact of the exotic or it’s potential ramifications. Experts are not only unsure about what, if anything, to do about the presence of these fishes… but they cannot even agree on the specific source of the introduced specimens!

While some scientists and investigators would like to ascribe the establishment of exotic species to hobbyist release of pet specimens, the practical reality as I see it makes this a highly unlikely explanation. To begin with, it seems implausible that enough individual hobbyists would coincidentally decide to release enough specimens near enough to each other on a reef to found a colony of exotics. Furthermore, unwanted specimens are often overgrown, unfit from a captive life, and generally suffering from inadequate food (e.g. - thyroid problems from iodine deficient foods) and poor exercise in small home aquaria. They simply lack conditioning to find and compete for food on a wild reef, not to mention avoiding the perils of would-be predators. And even if they acclimated to the wild waters sufficiently… the odds of so few specimens finding each other on a reef, at the right time (s) to spawn, seems small. Then, the small batches of larvae from a successful spawn would have to survive on alien plankters in alien currents on an alien reef. Beyond that, enough of these larvae would need to successfully settle out and then grow to maturity in such (initially) small population numbers to then find each other some years in the future to spawn with hope for continuation. The statistical likelihood of a favorable outcome to individual releases of pet fishes being the origin of these exotics is slight, to say the least, in my opinion.

Caution: Pterois volitans can quickly outgrow small home aquaria! Photo Anthony Calfo

Another theory argued is that dive or tourism merchants seeded isolated patch reefs with imported batches of these fishes to improve revenue for their sites and attractions. As preposterous, if not nefarious, as the notion sounds, some significant aspects of the appearance of Lionfishes in the Atlantic do not exclude this possibility. In fact, there may be great credibility to the assertion. Investigators have complained that (some, not all) dive operators have been uncooperative with scientists seeking information on where to find Lionfishes on remote reefs. One could speculate that the merchants are protecting their “discovery”, if not their “investment.” As a possible founder source, it is at least consistent with early appearances of Pterois in North Carolina and beyond: most observations of the fish to date have been far offshore on isolated reefs at depth. These sites are miles away from the coastal waters where a hobbyist would likely spill and release a pet fish. And the likelihood of such poorly conditioned (captively grown) fishes swimming through vast stretches of open ocean to reach offshore reefs safely seems rather unlikely, compared to the chances of adults simply being seeded directly (by boat operators) on an isolated reef, or settling from larvae released or dispersed.

The release of pet fishes likely explains the appearance, albeit rare in number, of Indo-Pacific angels or tangs in Florida waters.  Platax orbicularis (L)  Photo by Robert Fenner  Zebrasoma Scopas (R).  Photo by Anthony Calfo.

This notion of larvae as the source of introduction is also quite interesting. One might wonder, initially, where would enough larvae come from to seed a reef to found a breeding population? How could eggs or larvae from the Indo-Pacific survive the trek to the Atlantic coast of America? On further consideration, though, carriage by boat with ballast water seems to be a plausible explanation. In fact, other fishes and invertebrates have been transported as contaminants this way. Notably, the egg masses of Lionfishes are sticky, durable and float. By this nature, they can easily come into concentrated contact with surface sailing boats. With this theory in mind, we can also see that North Carolina is home to some of the largest and busiest ports and shipyards in America. This situation is bolstered tremendously perhaps by the presence of naval ships. The unfortunate political realities in the Middle East have additionally spurred a number of military vessels to travel to the Indo-Pacific, Persian Gulf, etc. The possibility of piscine contaminants with many thousands of gallons of water being repeatedly transported by boats from afar is possible here, and is yet another remarkable theory

The Indo-Pacific Chromis viridis has been spotted in Atlantic waters.  Photo by Anthony Calfo

For what its worth, I honestly don’t have a strong opinion on what the principal source of Pterois was to establish a breeding population. All of the theories presented to date are equally possible and equally unlikely to me at the same time. Could hobbyists really be the source of the foundling population? Yes… I do believe it is possible. Especially if we have underestimated the span of time that occasional releases from private owners of unwanted fishes has occurred. Pterois spp. are indeed long-lived and obviously better protected (venomous spines) than most other fishes. Their establishment is not so surprising, whereas small numbers of other notable exotic species have been observed only sporadically through the years, such as Pomacanthid angelfishes, Acanthurid surgeons and tangs, and various small fishes such as Pomacentrid damsels. There is even a concern about the increasing appearance of Pacific Ephippid spadefishes (AKA “batfishes”) schooling with Atlantic species: the worry is that they will interbreed. Still, it is remarkable to me that enough specimens of any exotic can survive any of the proposed theories of introduction in the dynamic Tropical West Atlantic ocean to establish a colony. And whether you tolerate or dislike the reality of exotic introductions, it is at least testimony to the hardiness and adaptability of some amazing and beautiful reef fishes.

Resources and Bibliography:

Dr Robert Goldstein, “Lionfish in the Western Atlantic,” Seascope, Volume 21, Issue 2, 2004


MARINE ORNAMENTALS (conference) 2006 February 13-16, 2006 Las Vegas, Nevada for discussions with academics and industry professionals of aquatic science.

Q from a Scientist - Caribbean Sharpnose Puffers Nipping Off Fish Spines?   8/22/11
Hi there,
<Hello Merritt here.>
I'm a graduate student doing some work on lionfish down in the Caribbean and witnessed an unusual interaction between invasive lionfish and a Caribbean Sharpnose Puffer (Canthigaster rostrata) that I'd be curious to hear your take on!
<Great! Helping with the lionfish invasion are you.>
During the capture, handling, and tagging of lionfish that makes up the bulk of my project, the skin covering the venomous dorsal spines of lionfish are often tugged down as they poke through the collection nets. On one occasion, after one such fish was released from its bag and was sitting on the reef recovering, a Sharpnose puffer came over and began biting at the exposed portion of the dorsal spines. On fish re-sighted after tagging, these exposed spines are often shorter and blunted, as though the exposed end has been bitten off. I was just wondering if your team has had any experiences with Sharpnose puffers biting off fish spines in the past, and on what might cause this behavior?
<Actually I have personally witnessed puffers of many species exhibiting this behavior in an aquarium. I can only assume in an aquarium that the behavior is either one of territory defense or two them being typical puffers.>
I know they're known for biting in close quarters, but this didn't look like a territorial encounter as the puffer looked more like he was grazing or investigating a snack than trying to drive the lionfish off. I wondered if there's any nutritional benefit to puffers from nipping fins or spines that might explain this?
<None that I know of.>
I've benefited from the wisdom of WWM many times before, and recognize that for many of the less-studied marine ornamentals, hobbyists probably know more about behavior than academics, so I look forward to hearing what you think. Thanks a million!
<From what I have seen puffers tend to be very curious creatures and tend to bite things/objects to figure out what they are. Others will just pick on tank mates (especially lionfish) by nipping their fins and/or harassing them until the fish is removed or dies. I will assume this observed behavior to be of curiosity and obnoxiousness that makes up a puffer personality than for nutritional benefit. Good luck on your research and hope that you find a solution to the lionfish invasion. Merritt>
Natascia Tamburello
MSc Candidate
Tropical Marine Ecology Lab
Department of Biological Sciences
Simon Fraser University


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