Observations of a Nerd

Can we overfish the lionfish?

Posted by Christie Wilcox on May 11, 2011
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Lionfish are one of my favorite animals (I study them, after all). They’re stunningly beautiful. Of course, they’re also a devastating invasive species. Though they’ve only been in the Atlantic Ocean for some 15 years or so, they’ve taken over reefs, eating everything in their path. They’ve been found to reduce the recruitment of native fish by 79% on average, and are occurring in densities 8 times higher than in their native range. To say they’re bad is an understatement. The damage is so severe that they were listed as one of the top 15 threats to global biodiversity in 2010.

There’s little hope that the reefs will adjust to their newest members on their own. Lionfish are armed with an array of venomous spines, and aren’t known to have natural predators even in their native range. They spawn year round, producing millions of eggs each time. Estimates place the founding population in the Atlantic below 10 individuals; now, you can find that many on a single head of coral in the Bahamas. Though they’ve been invasive for less than two decades, the lionfish are already having ecosystem-level effects. The local reefs simply don’t have time to figure things out for themselves.

So it’s up to us to combat this invasion. Already, areas with high infestation rates like the Bahamas have launched a full-on assault. The goal: kill them. Every one of them. Period. So-called ‘lionfish derbies’ can round up thousands in an afternoon, and local communities have begun trying to eat the lionfish out of their reefs by promoting them as a delicacy. But the big question is, is such a plan going to work?

That’s what Andrew Barbour and his colleagues from the University of Florida decided to investigate. To do so, they took fisheries management math and turned it around. Normally, fisheries ask the question “how much can we catch sustainably?”, with the goal being to maximize the catch at each size of fish without causing a collapse. Instead, Barbour and his team wanted to know how much we’d have to catch to cause a collapse. In other words, how many lionfish do we have to take to overfish them?

Of course, not everything is known about the lionfish populations in the Atlantic, so the team simulated many fisheries scenarios to come up with a minimum catch needed to collapse the lionfish fishery. Depending on the natural mortality rate, they found that we need to fish 35% – 65% of the population. Given estimates of density, they estimate that we need to remove 157 – 293 lionfish per hectare per year. If we just count the 52,000 km2 of coral reefs in Caribbean Sea, that translates to somewhere between 800 million and 1.5 billion lionfish annually. That’s a LOT of lionfish.

Even more sobering, though, is that when they estimated how long it would take the population to rebound if fishing pressure decreased, the scientists found that the lionfish could recover in as little as 6 years. So not only do we need to catch upwards of 50% of the lionfish out there, but we can’t stop. We can’t just fish them out and then relax. We have to constantly keep the pressure on the population, or they’ll come right back.

In the end, the authors conclude that intense, sustained fishing activity would be required to even have a shot, and that even that is unlikely to succeed in managing lionfish populations “it cannot be assumed,” the authors write, “that any level of lionfish removal will be beneficial to native aquatic communities.”

Attempts to do so might even backfire. By killing larger lionfish, for example, the authors caution that we may serve as a selective pressure towards a higher density of smaller sized lionfish which would eat more juvenile native fishes.

We like to think that if we just came up with the right strategy, we can solve problems like the lionfish invasion. That we, as the smart, capable being that we are, are able to overcome any obstacle and take on the role of caretaker of our natural world. Sure, we might make mistakes, like introducing the lionfish to the Atlantic, but we can fix them, too! Right?! But results such as these show that we’re not as powerful as we think. There may be absolutely nothing we can do now that the lionfish have invaded, except to watch the massacre and see what survives.

ResearchBlogging.orgCitation:
Barbour, A., Allen, M., Frazer, T., & Sherman, K. (2011). Evaluating the Potential Efficacy of Invasive Lionfish (Pterois volitans) Removals PLoS ONE, 6 (5) DOI: 10.1371/journal.pone.0019666

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Comments

  1. #1 Coward
    May 11, 2011

    You should warn readers to buckets of death so it doesn’t shock them! Some of us are marine aquarists and love our lions. ;) Although I do love the irony of aquarists setting up tanks to preserve what ocean life we have left, while its still here, meanwhile others are purposely trying to kill as many creatures as possible.

    It might be noted that these fish were introduced by shipping vessels that take on large amounts of water in one part of the world and then dump it back into the ocean in another part. Thus, lionfish larvae, among other ocean creatures, are introduced to non-native regions. Without controlling the introduction method, fishing them wont solve the problem and they will establish themselves just as fast as breeding.

    Here’s a picture of my lion (P. antennata):
    http://i55.tinypic.com/2i0uouv.jpg
    He may look cute but he spits water when he’s hungry. Which is always.

  2. #2 herky stubby
    May 11, 2011

    I didn’t know that lion fish are becoming pests in oceans. SOrry for my term.
    But I really like lion fishes. They look so brave.

  3. #3 TheRealSpo
    May 11, 2011

    Would it be possible to contain the invasion through hunting? I know they’ve made it into and around the Florida coast, but the populations here seem much less than their Bahama brethren. (I dive around Miami a lot, so my evidence that the populations are smaller here is anecdotal, so take that for what it is.)

  4. #4 ResCogitans
    May 12, 2011

    how long does a species have to live somewhere before that area becomes its ‘native region’?
    on the short (human lifespan) timescale perhaps people will view the change in biodiversity as bad, but on longer timescales evolution will ensure a balance.

  5. #5 annieols
    May 12, 2011

    @coward:
    The most likely vector of the invasive lionfish population is many accidental and deliberate releases of captured specimens. There is a theory about lionfish larvae in ballast water, but there is no evidence to support this theory (however, we do know many invasive species are transported this way so we cannot totally discount it). if you do some basic research on this HUGE problem you will find most scientists dont think that LF were transported this way..

    Great blog! thanks for passing on this paper! I have created a Lionfish Awareness and Elimination scuba course in Bonaire and we are having some sucess, but this model puts things in perspective a little more clearly. It varies a little from the Morris model however, and i am wondering if you have any thoughts on which model you would consider to be more accurate?

    Thanks
    Annie O

  6. #6 Joe
    May 12, 2011

    Are they tasty?

  7. #7 JM
    May 12, 2011

    But, do they taste good?

  8. #8 Tom
    May 12, 2011

    Even if they don’t taste great – do they taste palatable enough that they can be shredded into fish sticks or pig food and such.

  9. #9 James
    May 12, 2011

    The fish don’t have to be eaten to be useful. In fact, catching, filleting, distributing… all according to regulatory standards… that’s difficult! All that fish could probably be useful as a local fertilizer or fish meal for aquaculture, though.

  10. #10 Ellen M
    May 12, 2011

    Yes, they are very tasty! Eat more lionfish!!

  11. #11 Calli Arcale
    May 12, 2011

    Lionfish are gorgeous animals. Simply beautiful. (My husband disagrees; he thinks they’re hideous. I guess it’s in the eye of the beholder.) But fishing them out seemed impractical before; I didn’t realize how just much so. To me, one of the major problems is that fishing involves bycatch. There’s no way we can fish them to extirpation without severely damaging other fish populations in the area. They’re a good target for no-limit fishing (except for how careful a fisherman has to be with those spines — the venom is excruciating), except I do have to wonder just how you go about processing the fish without risking excruciating agony if you get poked by a fin.

  12. #12 Richard
    May 12, 2011

    Great (if depressing) article,

    I was wondering, is it known what keeps lionfish under control in the Indopacific? I’ve dived around the western Indian Ocean for a while, and I don’t know of any species that would actively predate lionfish -the spines appear to be just too effective. Am I just missing something?

    Best regards
    Richard

  13. #13 cat
    May 13, 2011

    that translates to somewhere between 800 million and 1.5 billion lionfish annually. That’s a LOT of lionfish

    Lez maek cooperashun

    U gez fish in canz we taeke care of rest
    >3

  14. #14 Eric Heupel
    May 13, 2011

    Great article Christy (as usual!) I too have a love hate relationship with Lionfish… Love them in the Indo-Pacific, hate them in the Atlantic.

    As a not (for further depressing info) our DSO just got back from a second trip deep diving the Bahamas (diving on a 6000′ drop wall = AWESOME! if slightly scary!) They saw Lionfish below 350′ and in one dive counted 8 below 200′

    That’s a pretty significant number (from one dive) below recreational diving depths, and in areas that really aren’t fishable by surface fishing methods.

  15. #15 andrewrobcampbell
    May 13, 2011

    Great article! Do you know what method of fishing they would use to catch them (i.e. jigging, longline etc.)? As was previously mentioned by-catch would become enormous. Even if you conservatively estimated a 10% by-catch rate, that would equal 80-150 million non-target species based on the given 800 million-1.5 billion range. You could use a more target method of fishing (like jigging or trolling) but the fishing effort needed would be huge!

  16. #16 Kelly
    May 14, 2011

    Thanks for the great insight into the science behind controlling lionfish populations. I was on my first SCUBA trip in Mexico when my guide nonchalanty speared one and fed it to an eel. I was shocked and annoyed, even as I understand the invasive species issues. I blogged about this recently: “An attractive enemy: impaling invasive lionfish”

  17. #17 Isabel
    May 14, 2011

    Kelly,

    I read your blog post, and I can understand your dismay at your divemaster’s actions, but I found the quote you posted very disturbing. It came very close to calling those who care about native communities “racists” an ignorant complaint that pops up regularly. Also what does the author mean by “in America especially”? Are you SURE you understand invasive species issues?

    “In last week’s New York Times Sunday Opinion section, anthropologist Hugh Raffles commented smartly upon cultural attitudes about human and ecological immigration. Throughout history (and in America especially) he asserts, “our natural landscape is a shifting mosaic of plant and animal life…Designating some as native and others as alien denies this ecological and genetic dynamism.” The problem of invasive species, Raffles argues, has as much to with cultural perception as scientific analysis. “It draws an arbitrary historical line,” he concludes, “based as much on aesthetics, morality and politics as on science, a line that creates a mythic time of purity before places were polluted by interlopers.”

  18. #18 Isabel
    May 14, 2011

    “Today, a species’s immigration status often makes it a target for eradication, no matter its effect on the environment.”

    This is just ignorant. “Naturalized” and “invasive” are meaningful terms. I know of no non-destructive non-native plants that are targeted for eradication. Do you? I also know of many naturalized non-natives that are considered affectionately by those active in eradication of destructive species. This is just total bullshit that the author is making up. How do people get away with this.

    “Or take ice plant, a much-vilified Old World succulent that spreads its thick, candy-colored carpet along the California coast. Concerned that it is crowding out native wildflowers, legions of environmental volunteers rip it from the sandy soil and pile it in slowly moldering heaps along the cliffs.

    Yet ice plant, introduced to the West Coast at the beginning of the 20th century to stabilize railroad tracks, is an attractive plant that can also deter erosion of the sandstone bluffs on which it grows.”

    And deterring erosion stops natural processes which is part of the problem for the native species. Same with Pampas grass, planted for a similar purpose. We are going from a black and white, simplistic view, where our goal is to control nature, to a more subtle view of how nature works, which is really the *exact opposite* of what this author is suggesting.

    “Last month, along with 161 other immigrants from more than 50 countries, I attended an oath-swearing ceremony in Lower Manhattan and became a citizen of the United States. In a brief speech welcoming us into a world of new rights and responsibilities, the presiding judge emphasized our diversity. It is, he said, the ever-shifting diversity that immigrants like us bring to this country that keeps it dynamic and strong.
    These familiar words apply just as meaningfully to our nation’s non-native plants and animals.Like the humans with whose lives they are so entangled, they too are in need of a thoughtful and inclusive response. ”

    Oh gag me I can’t stand it! He is talking about people from different cultures, yet all of the same species, all with the same biological needs, and comparing that “strengthening” diversity with species diversity? Never mind the fact that invasive species very often lead to less diversity, which is what biologists are trying to combat!

    I can’t believe this was published in the New York Times. I hope there was a strong scientific rebuttal from someone who wasn’t talking out of their asshole like this dude.

  19. #19 Isabel
    May 14, 2011

    Sorry for the spam, but I found an excellent, detailed and eloquent point for point rebuttal to Raffle’s NYT essay (which apparently and justifiably has outraged scientists):

    http://ipetrus.blogspot.com/2011/04/invasive-response-to-mother-natures.html

  20. #20 Jack Bulton
    May 15, 2011

    I think we will still likely to think that we will come up with the right strategy to sort this lionfish problem…or will we? Great article Christie…

  21. #21 RobbieC
    May 16, 2011

    How about a cite for the “top 15 threats to global biodiversity?”

    The argument about non-native species can be clarified by observing that non-native, non-destructive invasive species increase biodiversity while non-native, destructive species (like the lionfish) decrease biodiversity by destroying native species.

    CW: Horizon scan of global conservation issues for 2011

  22. #22 Buy Gifts Items
    June 4, 2011

    I didn’t realize how just much so. To me, one of the major problems is that fishing involves bycatch.