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Diving Deeper: Invasive Lionfish - King of the Reef

Episode 37 (Apr. 5, 2012)

HOST: Welcome to Diving Deeper where we interview National Ocean Service scientists on the ocean topics and information that are important to you! I'm your host Kate Nielsen.

Today's question is...How do we respond to invasive lionfish?

In less than a decade, lionfish have become widely established across the Southeast U.S. and Caribbean. Recent estimates of lionfish densities indicate that lionfish have surpassed some native species with the highest estimates reporting hundreds per acre in some locations.

Today we will talk with Dr. James Morris on lionfish. James is an ecologist with the National Centers for Coastal Ocean Science, and James, welcome to our show.

JAMES MORRIS: Thank you, it's good to be here.


HOST: So James, can you tell us what an invasive species is first?

JAMES MORRIS: Yeah absolutely. There's lots of different definitions for invasive species but one that we defined by law actually is a non-native species that causes either, and most of the time it's both, economic harm or ecological harm to a new environment.

HOST: Where is the lionfish actually from?

JAMES MORRIS: Lionfish, there's actually two species of lionfish that were introduced into the Atlantic, the red lionfish or Pterois volitans and the devil firefish, Pterois miles. And the Pterois volitans, the red lionfish is from the Pacific Ocean and it's distributed as far as Australia and the Pacific Islands. The devil firefish is actually from the Red Sea and Indian Ocean region and they tend to overlap in terms of range in Indonesia. The native range is very broad and they've now become invasive.

HOST: So, how did they get then into our waters, in the Southeast U.S., Caribbean, kind of that region?

JAMES MORRIS: Well, we're not 100 percent sure because no one actually observed someone releasing lionfish into the Atlantic, but we have a few clues. One clue is that lionfish were heavily imported in the past into the U.S. They are a very popular marine ornamental species, people like to hold them in their aquarium and have them as pets. They're very beautiful, very ornate fish. They're kind of exotic because they are a scorpion fish, they are venomous, and just by virtue of their presence and their volume being imported to the U.S., we suspect that they were probably released from the aquarium trade.

HOST: And why is it then that the lionfish population just seems to be kind of exploding, just increasing so greatly in our waters?

JAMES MORRIS: Sure, well, to really look at that, let's go back for a second and talk about the timeline here. The first record that we have of lionfish being introduced goes back to 1985. That was the first time that we have records of the lionfish being caught in the Atlantic, I think it was actually caught in South Florida waters. We had a number of introductions, a number of sightings, that occurred really between 1985 and 2000, but it really wasn't until 2000 that multiple individuals were starting to be observed actually off of the coast of North Carolina and until that time we'd only had a few individuals off of the coast of South Florida.

That can be termed the lag phase of the invasion. We see this with many invasive species where you go through a period of lag, where there's not critical mass in the population for that population to become truly invading or under exponential growth rate. And so, we're at the point now where the invasion is rapidly increasing, it has been for some time, both in terms of geographical spread of the invasion, but also in terms of increasing local densities.

HOST: Is it likely that the population's going to keep growing at this kind of rate?

JAMES MORRIS: Yes and definitely in some locations. So, the geographical spread of lionfish is continuing. Lionfish have in the last 10 years completely invaded the offshore waters of the southeast U.S. They've invaded the Caribbean. They have reached as far south as the lower southeastern Caribbean islands, the West Indies, as far south as Guadalupe, Trinidad and Tobago and those areas. We expect they will continue to spread south until they are limited by the actual cooler waters of South America, probably around the coast of Argentina is when the water starts to become cool again, and lionfish of course can't live in cold water because they're a tropical fish.

It is really astounding when you look at the geographical spread, at how quickly that invasion has occurred and it just teaches us so much about the connectivity of ocean currents and the spread of an invasive species and the importance of prevention because once they are loose, there's nothing really that we can do about it to prevent their spread in such large ocean systems like this.

HOST: So let's understand a little bit more about the lionfish. They don't like the colder water temperatures like you're telling us. What do they like to eat?

JAMES MORRIS: Lionfish are largely fish eaters especially when they get older. They do eat of course crustaceans and small crabs and shrimp and things like that during their younger lives. As juveniles, many fish eat those smaller crustaceans, but as they get larger they become largely piscivorous which means that they largely are eating fish.

What they're eating in terms of the specific species depends on the habitat that they're in, the region that they're in. So we find that they're largely generalist predators, they eat mostly what is most abundant on the reef, which makes a lot of sense in terms of the energy that they have to expend to eat. Their diet really reflects the local fish community. Now that can be a problem in some places for sure because if lionfish ever recruited to a particular reef that is important habitat for economically important species like snapper, grouper, or others, they eat snapper and grouper as well.

HOST: So they can eat these other economically important species like you're naming - snapper and grouper. Do they take the food sources away from other fish as well?

JAMES MORRIS: Yes, possibly. One of the things that we have learned about lionfish over the last several years is that their impacts can vary. It can vary in terms of the health of the local fish community. It can vary in terms of the recruitment rates that lionfish are recruiting to some of these new habitats. Their local densities definitely play a very important role in the overall impact that lionfish are having on the local food web.

HOST: Are there predators for the lionfish?

JAMES MORRIS: That's a good question and a very difficult one to answer. We have to sort of go back in time a little bit and talk about lionfish in their native range. Many people have asked and we've been looking for years, what may eat lionfish because that's sort of what we're used to keeping species in check is, are their natural predators. And we really have no evidence of a consistent natural predator of lionfish in their native range. We have a few instances of incidental, one-time events of predation. What we don't have are diet studies of predators that eat lionfish that show that they're eating lionfish on any type of consistency. And that's important for predation to be an impact on the natural mortality, the predation mortality, of lionfish.

We've also been looking in the Atlantic and we haven't found a predator that is consistently feeding on lionfish to the extent that it appears to be controlling their local densities. There's lots of Atlantic predators that have eaten a lionfish, we've got documentation of a grouper species eating a lionfish or an amberjack or cobia and the list goes on, many species now, but what we don't have is any consecutive evidence that those predators are preying on lionfish.

We're looking. That is an important question and one that as our native reef fish adapt to the presence of lionfish as we're curious if some of our Atlantic reef fish predators may adapt to prey on lionfish. And it also has a lot to do with the densities of lionfish in the range and that's an important finding and one that we don't have a whole lot of information about.

HOST: So for our listeners today, it's important to note, lionfish need warmer waters which is why they've expanded into this new geographic region. They seem to have a lot of food available that they're able to keep going and we're still exploring if there is that consistent predator. Are there other factors of lionfish that contribute to this invasion?

JAMES MORRIS: Sure, well let's talk about this predator thing for just a second and place it a bit in context. First of all, lionfish is a venomous fish. It evolved a venom defense system in its native range that is very effective.

It also has this aposematic coloration that warns potential would-be predators that, "hey don't me because I'm a venomous fish." Our Atlantic reef fish recognize that coloration pattern, it's this universal coloration pattern as being a venomous fish so we've done laboratory trials and demonstrated that some of our native reef fish like black sea bass and even some groupers on a small number of trials, clearly identify lionfish as a non-palatable prey item because of that venom defense. And even when we look at the interactions between this juvenile lionfish and grouper black sea bass species, we find that they really avoid at any cause trying to interact with them because of that venomous defense.

HOST: And by venomous defense you mean, if another fish tries to eat a lionfish then that fish can die?

JAMES MORRIS: Well, that fish will get stung by the venomous spines and it makes for an unpleasant, in some cases, experience. Now you can have instances where a large predator could eat a small lionfish and not get envenomated because the small lionfish can go directly to the stomach without getting caught in the esophagus and envenomated by the spines and whatnot. But in cases where the predator is smaller, it makes for a very unpalatable prey item.

And the lionfish venom is a neurotoxin. It's a very potent neurotoxin and it can cause quite a sting in humans, we've known that, and we've been looking at that for some time, but it didn't evolve to protect lionfish from humans, it evolved to protect itself from potential would-be predators on the reef. That venomous defense has been so effective in the past that other species have evolved to mimic lionfish to keep from getting eaten.

Like the Indo-Malayan octopus, for example. One of the species that this very intelligent octopus mimics, along with sea snakes and poisonous fishes and things like that, is the lionfish because it has adapted and evolved to know that if it could look like a lionfish, it could keep from getting eaten. So to me that is such strong evidence that this venomous defense is very effective and is playing a role, in probably a big way, in how this invasion has come to be so aggressive.

HOST: So, it's kind of a perfect storm then, I guess for the expansion of this invasive species.

JAMES MORRIS: There are lots of parameters, there's lots of ways that we could talk about that lionfish have become invasive, there's reproductive biology, their growth rate, their generalist appetite, their generalist diet - there's lots of key indicators here that point to lionfish being almost, if we had to build the perfect invader, lionfish have a lot of those characteristics that we'd probably put on paper that have led to this invasion.


HOST: So, what can we do, what can humans do, to help with this lionfish invasion?

JAMES MORRIS: Well, the first thing we can do is stop releasing non-native species. We've got to work harder and do a better job of informing the public about the impacts of invasive species. In terms of lionfish and what we can do specifically about this invasion is we've been working hard over the years to educate the public about the problem of lionfish and more importantly the possibility that we could control lionfish in certain locations. We don't believe, for a moment, that we can eradicate lionfish. We just don't have the technology, even if we wanted to go out and remove all the lionfish out there, we wouldn't really know where to go look for them all. We just don't have that good of habitat maps, especially in the southeast U.S. And it's just the expanse. Lionfish inhabit out to 1,000 feet and up to less than a foot of depth in some locations and so their habitat is very broad and wide.

We are looking at control plans for certain locations. We've been working with the National Park Service, National Park Service has done a wonderful job of developing a national lionfish response plan, working on control plans within National Park Service areas impacted by lionfish. We believe that we can make a difference in certain locations. Locations that are small, have boundaries, that have the infrastructure to control their local densities for conservation mandate. And we believe that we can work to control them in national marine sanctuaries in similar ways that we can in our national parks. But that requires programs and that requires that we can organize in how we can do this.

We have found that harvesting lionfish as a food fish is a potential way that you can encourage removals and provide long-term incentives for removals. Now, there's a bit of controversy around that because we don't want folks to, because of having a positive experience being able to harvest lionfish, to think that might make it a good idea to produce other non-native species because you could fish them as hard as you want to and that's a bad idea because there are unintentional consequences of those kind of things. But we do know that really harvesting them as a food fish really is the best thing that we have on the table in terms of creating a long-term incentive for removal.

HOST: And that's even given their venom defense, we're talking about harvesting as a food source. So it is safe to eat and handle lionfish?

JAMES MORRIS: It is. It's safe if you handle it properly. We need to be clear in that there's a difference between a venomous fish and a poisonous fish. Poisonous fish is a fish that essentially has a toxin or poison in its flesh, that you will get sick from eating it. A venomous fish is a fish that has a venom somewhere in its body, it's usually not in the flesh, that would be poisonous, but along the spines or in the teeth or some type of bony structures of the fish. In the case of lionfish, the venom is located only in the spines of the fish, it has dorsal, pelvic, and anal spines. The venom glands are located along grooves of the spine. There is no venomous sac at the base of the spine as is commonly said. That venom gland actually goes along the grooves of the spine. If those spines are removed before cleaning the fish, then there's no risk there. There are field guides. There are lots of instructions now that are available to help people learn how to clean the fish.

HOST: Let's talk a little bit about NOAA and NOAA's efforts and what folks are even doing at your office, things that might currently be underway to help with the lionfish problem.

JAMES MORRIS: Sure. We have a research laboratory, we're in the Center for Coastal Fisheries and Habitat Research in Beaufort, N.C., which is one of the centers within the National Centers for Coastal Ocean Science in the National Ocean Service, and our laboratory has been working to understand the biology and ecology of this invasive species. We are concerned about lionfish really from a pollution standpoint.

Lionfish are a biological pollutant. We have been doing a number of biological and ecological assessments over the years, we have some great people at our laboratory that have been doing fieldwork. One of those is Paula Whitfield, she has been doing diver surveys, counting lionfish, looking at the impacts on the fish community in temperate waters, mostly off the southeast U.S. That work really provided a lot of the foundational understanding of the invasion and how the densities of lionfish are increasing and tracking the overall invasion by monitoring a few sites.

Over the years our work has progressed more to tropical systems and working with the Florida Keys National Marine Sanctuary for example, in developing control strategies, developing a lionfish action plan at the sanctuary. In the meantime, while we had to work along with managers to address the issues, we've had to keep doing science at the same time to inform the managers about what actions to take and about the biology of this particular invader. Those are just some examples of the kinds of things we've been working on.

HOST: And maybe you can help us understand, how do scientists monitor or do counts of the species especially in the water where they're so mobile - there's currents, there's so many things happening, what is that like, what goes into doing a species count?

JAMES MORRIS: There are a number of ways to assess fishes. You can do it from boat with things like acoustics technology. You can do it by setting gear, by fishing, by setting traps, or hooking lionfish to try to get a sense of the local population from the numbers that you have there in terms of catch per unit effort.

In the case of lionfish, most of the density assessment work that has been done have actually been done by divers or remote operated vehicles. And there are several different methods for diver surveys that we use. We actually are working on a manual now that provides guidance to scientists and field workers on how to effectively monitor lionfish densities using things like a roving diver transects and different types of methods and strategies.

HOST: So James, for our listeners out there today, is there any action they can take to help with the lionfish problem? Anything we could pass along to them?

JAMES MORRIS: Yes, there is. One of the things that we can do with this problem is use it as a poster child. It has been amazing to me how much kids like to learn about lionfish. How much they learn by talking and learning about this, not just about the problems of invasive species, but about conservation and about marine science and marine resources, even NOAA, and how we can teach them about the problem of invasive species.

On a local level, if you live in south Florida, become involved. There are derbies that happen regularly that are organized to go out and remove densities of lionfish. There are adopt a reef programs that are springing up in the waters of the southeast as well as the Caribbean and even in the Gulf of Mexico where folks are taking responsibility for their local environment and going out just like we would do a beach clean, they would go out and remove lionfish and work to conserve a little piece. If there is a silver lining in this invasion, it is really that it has educated us on the problems of invasive species and that we hopefully can use this to message about the overall problems of invasive species really as biological pollutants and things that we want to keep from happening in the future.

HOST: Thanks James for joining us on Diving Deeper and talking more about lionfish. To learn more, please visit

That's all for today's show. Please join us for our next episode in two weeks.