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HOST: Welcome to Diving Deeper where we explore important ocean topics with National Ocean Service experts. I'm your host Kate Nielsen.
Today we will have part one of an update on the invasive lionfish since our last interview on this topic in April 2012. We'll focus a little bit on the spread of the lionfish and just some basics of lionfish in general in today's discussion. Back to talk to us today is James Morris with the National Centers for Coastal Ocean Science. Thanks James for joining us again on Diving Deeper.
JAMES MORRIS: Hi Kate, so glad to be here.
HOST: So James, for our listeners today who weren't with us for our last episode, can you highlight just a few of the basics about lionfish?
JAMES MORRIS: Oh absolutely. So lionfish is an invasive species. It's actually the first marine reef fish that has become invasive along the southeast U.S., Gulf of Mexico, and the Caribbean. It's a scorpion fish so it actually has venomous spines that can sting people as well as are used for predator defense. Lionfish first were introduced in 1985, is the first record that we have of them. Since the mid 80s, they've spread to include basically the entire region and are invading coral reef and hardbottom reef habitats and are really quite a concern.
HOST: OK and a beautiful fish, at least from what I've seen from the pictures, beautiful but quite problematic.
JAMES MORRIS: They're very beautiful, as a matter of fact, that's why they're here. They were largely, we believe, released from the aquarium trade. We believe that there was probably no single introduction that there were multiple introductions over a period of time. We certainly have some diverse genetics in the population that suggests there were at least nine female lionfish that were released. We are certainly concerned from a management perspective in terms of the ecological impacts that they can have in the reef systems and need to be more concerned about the release of non-native species.
HOST: Ok, so in the past year then, since we last talked, what has changed with the status of the lionfish?
JAMES MORRIS: Well the lionfish invasion continues to spread rapidly. We're continuing to see them grow in densities along the southeast U.S. and especially in the last year or two in the Gulf of Mexico. So lionfish now are found as far north as North Carolina, they can be found farther north than North Carolina in the late summer where some of the tropicals actually are transported north along the Gulf Stream and recruit. Tropicals don't live over winter so lionfish like other tropicals will die north of North Carolina. We also see lionfish as far south now as the coast of Venezuela. So the entire Caribbean, Gulf of Mexico, southeast U.S. is now the new habitat of lionfish.
HOST: And a lot of this change did happen over the last year?
JAMES MORRIS: So over the last year to two years, the invasion to the Gulf of Mexico and of course that that southward march continues to occur.
HOST: So we know that the lionfish is continuing to spread to new regions - moreso as you're saying over this last year to two years. But is there any kind of limit then to where the lionfish will spread because they don't like the colder water temperatures? What is too cold for a lionfish?
JAMES MORRIS: So we know from laboratory experiments, looking at the thermal tolerance that lionfish will stop eating around 13 to 14 degrees Celsius. They perish at around 10 or 11 degrees Celsius. And there's some error around those particular temperatures. And so that places their southern limit, based on sea surface temperatures, somewhere around the northern coast of Argentina and as far north as North Carolina.
HOST: In this range that we've talked about, do lionfish have a preferred habitat, are they spread out pretty much the same density throughout the region or do you see hot spots of lionfish?
JAMES MORRIS: Absolutely, we do see hot spots. Lionfish are a reef fish and they're associated very much to habitat that has high relief. We see high lionfish densities specifically around artificial reefs like shipwrecks, we see them around in coral reefs where there's large relief height, but we also do see some lower densities of lionfish and general occurrence in some of the lower relief habitats. One of our questions right now is what are our densities of lionfish in the deeper habitats, some of these coastal systems, and we really need to work on that and try to understand more about their deeper water densities and habitat preferences.
But by and large the general trend is that lionfish really prefer those high relief habitats. We see large numbers many times around even bridge pilings or sea walls, we can find numbers there, it can be somewhat patchy, some reefs will have higher densities than others, some have been invaded for longer periods of time so there's been larger populations that have been recruited there, so it really depends on the region that you're talking about and the length of time that the invasion has been happening there, and the types of habitat that exist there.
HOST: So they really are just spreading like wildfire it seems and they keep multiplying. What can you tell us about lionfish reproduction? How does this play into the whole lionfish invasion?
JAMES MORRIS: Yes, that's a good question and it's one that we've been working on for a long time in our laboratory. The reproductive biology of lionfish was really something that interested us from the very beginning. We were wondering how is this invasive species reproducing so quickly and what is their reproductive biology look like. Interestingly there really have not been a whole lot of reproductive biology done on this species in their native range so there was a lot of really uncertain questions that we had to address from the beginning such as: how often do they reproduce, how do they reproduce, how many offspring do they release over time, and some of those basic questions. What we've learned over the years has been quite alarming and certainly the reproductive biology has in some way influenced or even facilitated such a rapid and aggressive invasion.
We've learned that female lionfish can release more than two million eggs a year. We've learned that they release them in gelatinous egg masses that float at the surface. They release them often - about every three to four days a female lionfish can release eggs, we've seen that both in the Bahamas as well as off the coast of North Carolina. And as an invasive species, that reproductive strategy sort of hedges your bets in terms of being successful in recruiting to a suitable habitat. If you reproduce often and you have these pelagic eggs which become pelagic larvae and they float up at the surface for 30 days or more, then they will settle down to reefs that are far away and that can be an advantage I think from an invasion point of view that you sort of spread your risks, you spread your progeny throughout out a large range, and that likelihood of probability that you will be successful in becoming established increases when you spread that probability. So we are kind of fascinated by the reproductive biology.
HOST: So, let's talk a little bit about predators. Let's go first and think about predators in that natural environment and then maybe humans we can talk about a little bit afterwards. Can you tell folks why we haven't found a predator yet for the lionfish?
JAMES MORRIS: The predator question is a really good one and it's one that we get probably more than any other question about lionfish and it's one that probably is a little bit controversial because we get lots of reports of someone finding a lionfish in the stomachs of such and such species. And there's been over 15 or probably 20 accounts of different species that have been reported to me and to my lab about finding lionfish in the stomachs. The problem is though that we're not finding lionfish in the stomachs of any of these species with any regularity.
The other problem is that we really have very little evidence that lionfish populations are lower in density because of natural mortality associated with predation on for lionfish either for juveniles or adults. What we do have evidence though is that based on laboratory trials that we've done in our laboratory, certainly our native reef fish recognize the coloration pattern that lionfish have. It's a warning coloration pattern. It's universal in the animal kingdom. And our native predators, in these feeding trials, in the laboratory and even looking at behavioral stuff in the field, our native predators recognize lionfish as a venomous fish.
And that venom defense system is really, really effective. As a matter of fact and I like to teach this when we talk about sort of some of the evolutionary biology around the lionfish invasion is that there is a species of octopus called the Indo-Malayan octopus that actually mimics lionfish to keep from getting eaten. It mimics lionfish as an animal that it wants to look like because it has evolved to know that if it can make itself look like a lionfish it will have less likelihood of getting eaten. That tells us a lot about the effectiveness of venom defense. So we have to be cautious about the role of predators in controlling lionfish. Time will ultimately tell. Personally in my opinion, I'm more inclined to think that lionfish may compete with themselves as a limiting factor more than predation mortality. They will begin limiting their distribution. And classically that is the way of invasive species. Many times we see invasive species begin incurring intra-species competition or competition with themselves for resources rather than competition with other native species.
HOST: So there's no known, really strong, effective predator; lionfish continue to spread, they continue to cover more ground, or more ocean, than ever before. Do we need to stop the lionfish invasion? What impact are they actually having on the ecosystems that they're coming into contact with?
JAMES MORRIS: So, invasive species cause billions of dollars worth of economic damage annually. Some of the major invasive species problems include things like kudzu or Asian carp, zebra mussels. Some of these species, there are some termites for example that are invasive. When you think about the economic impact of invasive species, it is really, really high. Such is the case with lionfish. When thinking about the economic impact of this invasion, when you calculate the coastal resource managers staff time throughout the entire invaded range - which remember is from North Carolina to now Venezuela - when you calculate the impacts of predation by lionfish on economically important species like grouper and snapper, when you calculate the impacts to human health by people getting stung and interacting with lionfish, when you look at all of those impacts and sort of package it together, the cost, in terms of dollars is quite high. It's almost hard to fathom the cost that this single introduction is having.
The problem with invasive species that I think we still are gaining experience in sort of placing it context with some of the other coastal ocean stressors that we deal with is really placing it in a way that we can compare it. And one of the analogies that I like to use with lionfish is that invasive species is really a type of pollution. It's a type of biological pollution. We typically think of pollution as being something that's abiotic, we typically think of it as being something that's chemical, or something like noise pollution or light pollution or oil pollution. In biological pollution, like invasive species, can cause these same and sometimes even greater impacts than some of these other more conventional types of pollution. And so I like to compare lionfish really to like an oil spill or some other type of chemical pollutant. The difference though is that this is a living organism in that this type of pollution continues to spread, to reproduce and to get worse over time until it reaches some type of new equilibrium in the ecosystem. And then at that point the ecosystem, in this case the reef fish community, will never return to the state that it once was. You cannot clean up this pollution problem throughout the entire invaded range - we just do not have the tools and the ability right now, in terms of technology, to say we're going to get rid of all the lionfish. We wouldn't even know where to go look for all the lionfish from North Carolina to Venezuela if we wanted to. Certainly there's some fishing pressure that can be placed on lionfish, but that has its own level of challenges and so when we think about invasive species as pollution, it really places it in context to the other types of coastal ecosystem stressors and it's quite alarming to think of the scale.
HOST: So what happens then if we don't or if we can't stop lionfish?
JAMES MORRIS: Well, we are going to reach some type of new place - new equilibrium in the reef fish community that now includes lionfish. What I hope though is that we learn some lessons from this invasion about the importance of invasive species prevention and awareness. Did we learn some new lessons in terms of coastal ecosystem management and rapid response to non-native species to try to head off and keep something like this from happening again? We also though learn about the relative importance of this problem compared to some of the other types of problems.
We have the data now and there's lots of good scientists that are working on this problem. But the data is really showing very aggressive, ecological impacts from this single invasion. This is not something that just NOAA is talking about or working on, this is something that has been supported by National Science Foundation dollars to some of our academic collaborators and partners and all of the data show that significant impacts are happening. And my concern is that those are long-term impacts, that we can never really go back to where we once were within the entire system.
HOST: Thanks James for joining us and for giving us this update on lionfish. You can hear more about lionfish in the next part in this series where we will explore what can be done to help control this problem locally and specifically what NOAA is doing to help. To learn more, please visit www.ccfhr.noaa.gov/stressors/lionfish.aspx.
That's all for today's show. Remember, if you have questions on this episode or the National Ocean Service in general, you can contact us at firstname.lastname@example.org. And if you're on social media, don't forget you can find us, it's usoceangov, on Facebook, Flickr, and YouTube; and noaaocean on Twitter. Please join us for our next episode in two weeks.