Abstract
Red Lionfish (Pterois volitans) are invading the waters of Florida and the Caribbean at alarming rates. While it is unknown when they originally entered the ecosystem, their populations in the last decade have increased dramatically. While there has been thorough research done on the damage that they present to the environment, little has been done in considering long term control methods. This study proposes and discusses four methods of invasive species control that have been proven successful in other situations with varying similarity to this one. Through Natural Predation, Active Capture, Genetic Alteration and Introduction of Natural predators, we discuss the benefits and short comings that are associated with each control method. By analyzing available literature the feasibility of each method is discussed, but without further field research we may never understand how these propositions would affect lionfish populations in practice.
Introduction
Invasive species are no new threat to the U.S. and its economy, nonnative species have been entering U.S. waters and creating biological and economic impacts since the dawn of the Industrial revolution. While it is impossible to completely assess the damages that are done by invasive species, one source puts an estimate as high as 138 billion annually. (Morris and Whitfield 2009) recent years the populations of Red Lionfish (Pterois volitans) have skyrocketed in the waters adjacent to the state of Florida and neighboring tropical regions like the Bahamas. One study stated that between 2008 and 2010 their numbers have increased from23% to almost 40% of the predatory species total in some parts of this new range (Green et. al 2012). Though there are a wide variety of reasons that lionfish are causing major concerns, it is primarily because they prey on large quantities of small and juvenile reef fish, and predation on them cannot keep up (de Leon et. al. 2013). This has led to increasing concern amongst local fisherman and policy makers. Over the past few years there has been significant research done on lionfish and the species that they are preying on, but far fewer studies have been done to determine specific, effective methods of eradication or control (Green et. al 2012) (Morris and Whitfield 2009). To address this gap in currently existing literature, I have provided an in depth analysis of many of the preeminent studies that have been done on lionfish, and systematically compare and synthesize them with possible, feasible methods of eradication and control. Further discussion provides keen insight on four methods of dealing with lionfish that have been successful in other similar bio invasions and overpopulations around the globe. Through natural predation, active capture, genetic alteration, and release of natural predators, in the future the lionfish population could be completely eradicated, if not largely diminished.
Background
The first possible control method would be to limit or stop the harvest of large grouper species in the waters where lionfish are present. Some research has shown that in the areas where large grouper species are present, that populations of lionfish are more easily controlled (Mumby et. al. 2011). A second method, and one that is already partially in place, would be to increase the use of fish rodeos, and possibly even offer bounties on the capture of lionfish. This is similar to the method used to control nutria in Louisiana, and even though it has failed to eradicate them, it does help to keep their populations in check (Nutria in Louisiana Pamphlet). A third method, though likely controversial method, would be to introduce genetically modified individuals that would create barren offspring. There is not any evidence that this sort of research is being done for lionfish, but it has been done successfully with mosquitoes in other parts of the world (Lacroix et. Al. 2012). The last method, and probably least likely to be used, would be to follow the example set by the peacock bass, and release the lionfish’s native predators to the waters of Florida. This is probably the least likely method to be employed, but we can look to the success of the introduction of the peacock bass, and its ability to control other cichlid populations. On the other hand it is now a permanent staple in the environment of southern Florida.
It is unclear when exactly the onslaught of these fish began, but various reports show there appearance beginning sometime in the 1980s (Morris and Whitfield 2009). Having these fish living in Florida waters may not seem like a major issue on its own, but they are doing damage to local fish populations. According to one study conducted in the Bahamas, in areas where lionfish were present the population of some of reef fishes they prey on decreased as much as 65% from 2008-2010 (Green et al. 2012). These studies show lionfish are voracious predators, and since Florida is outside of their native habitat they have few natural predators (de Leon et. al. 2013). Another reason this problem continues to grow is the extreme birth of lionfish, which continues to propagate their populations throughout Florida and the Bahamas annual fecundity is estimated at over two million for adult lionfish (Morris and Whitfield 2009). In the long run, it is impossible to know what will happen to lionfish populations if they continue to go unchecked, but if the trends shown in some of these studies continue it may not be long before their numbers completely decimate dozens of native fish species.
In the wild Red Lionfish occur throughout the greater Pacific Ocean. They grow to a maximum length of about 15 inches and can live to be around ten years old (Luna 2015). In the wild they inhabit many environments that are very similar to those that are available in South Florida and the Caribbean (Morris and Whitfield 2009) (Luna 2015). They are known to eat a wide variety of smaller fishes and crustaceans, and also for their venomous spines (Morris and Whitfield 2009). These spines give them another level of defense that may make them even more difficult for non-native predators to prey on (Morris and Whitfield 2009).
In order to further explore the aforementioned control methods, and how they are relevant and feasible in the lionfish invasion, this study goes into depth explaining each one individually. It is important to understand that each one of these methods has been proven effective in another invasion or overpopulation scenario, and while all of these scenarios are unique in some sense, they do hold enough key similarities to merit consideration in realistically controlling invasive lionfish populations.
Literature Review
While there are some obvious gaps in current research regarding the lionfish invasion, there are a good many studies that have been done in regards to the issue as a whole. Additionally there are a good amount of government publications and reports and other studies on issues that hold a great many parallels with the lionfish invasion, that have provided invaluable data to this study. Though these studies and reports deal with other invasive species their methods can provide valuable suggestions that can be easily applied to the lionfish issue. The following has been broken down into three categories that will help better explain the types of resources that were available and the information that they may or may not have provided.
Scientific Studies on Lionfish
Of the resources that were used in this study seven them were scientific studies that pertained directly to lionfish. Though they all held different levels of value, they were all able to make some form of addition to the overall body of work. The majority of these studies were conducted in other parts of the Caribbean besides Florida, but most of the relevant information about lionfish behavior seems similar throughout the invaded territory. While these studies offer a wide range of valuable insights on the lionfish and the species that appear to prey on them, they do leave out any clear, feasible solution to the issue as a whole.
Diller et. al., Hackerott et. al. and Mumby et. al. are three of the studies that seem to have similar, albeit conflicting, themes in regards to the lionfish invasion. All of these studies focus on native predators, largely grouper, and how they can have an effect on lionfish populations. The Mumby study, which is the oldest of the three studies, offers the most simple, straight forward results. By stating that the lionfish populations are lower in areas where large native grouper are present they make a direct correlation between large grouper and smaller lionfish populations. In doing this they primarily state that grouper are preying on lionfish while also out competing them on some level. The Hackerott study was conducted with knowledge of the Mumby study in apparent attempt to falsify its results. Their results work to show that there are no direct linear results between lionfish and large grouper populations. While their survey methods do differ slightly it is difficult to discern which is more accurate. If they would not have directly mentioned the Mumby study it may have given the Hackerott study more credibility, but scientists trying to prove each other wrong is an inherent part of the scientific process. The Diller study, while similar to the other two, takes a more active approach in the management of the lionfish population. In suggesting a way to train predators, like grouper and sharks, to prey on lionfish a different perspective altogether is considered. Unfortunately all of three of these studies fail to propose any way their results could benefit or impede an actual management strategy.
The Albins and Hixon, De Leon et. al., Green et. al., and Morris and Whitfield studies are all good scientific studies that give basic background on the issue and how it is currently progressing, but the De Leon et. al. study is really the only one that begins to discuss management or its current effectiveness. These types of studies are important resources in a study like this, because understanding the background problem that the lionfish are creating is vital to understand the need for active management techniques. When an invasive species begins to establish itself, assessing the possible repercussions that leaving the animal unchecked are the basis for all the management propositions that are made as time goes on. The results of the De Leon study also offers early encouragement that active management policies can have an effect over an apparently short research period. Not to diminish the value of any of these studies, but they do not address the management issue that this one attempts to do.
Other Lionfish Resources
The Luna article is not intended to be used as peer reviewed scientific data, but it provided some extremely basic background information on the lionfish as a species. Fishbase.org is a valuable scientific resource that serves as an encyclopedia for fish species around the globe. Due to the possible scientific lapses that may be allowed in an article that was posted on the website of a conservation organization, the citations from “The Lionfish Invasion” posted on the website “Sailors for the Sea” was removed. Most of the information that was initially used was found to be mirrored in more scientific, peer reviewed publications. Since it was a vital resource in the early development of this study I felt that it still merited mention within this section.
Other Helpful Resources and Studies
The remaining resources do not specifically speak to the lionfish issue, but largely discuss or show results of how the proposed management techniques have proven valuable in other situations. The Hill dissertation and FWC peacock bass pamphlet discuss the success that Florida has experienced with the introduction of the peacock bass. Both would have proven more valuable if they would have provided more hard data on how the introduction of the peacock bass had a positive correlation in the declining tilapia population, but they are able to illustrate other positive effects of this ecological experiment. The excerpt from the Bomford and O’Brien book and the Nutria in Louisiana pamphlet are used to illustrate how the nutria invasion has been handled in other places. This information can easily be applied to the lionfish invasion. They both provide valuable insight, because in Louisiana it is framed as a management technique, while the Bomford book sites a successful eradication that took place in the UK. Lastly, the La criox et. al. study discusses the genetic alteration management technique, and how it has been proven to be successful in mosquitoes. While it is a very different animal and takes place on a much smaller scale, it does provide a small glimmer of hope to a technique that may not seem as applicable to fish.
Methods
To understand the potential alternatives to managing the lionfish invasion, I present a synthesis of the scientific literature on control methods used in studies of other invasions or similar overpopulations, and outline guiding principles for controlling lionfish populations. For each control method, data about the lionfish is compared to at least one study related to a control method of another species or of that of the lionfish itself.
When searching the key word Lionfish in any biological or scientific database dozens, if not hundreds, of sources may be provided. By referring to the invasion the vast number of resources were limited to fewer, more relevant sources. Though some sources did come from outside suggestion, Plos One, ProQuest: Science & Technology, and Thomson Reuters: Web of Science proved to be the most valuable. The majority of the useful articles used were gleaned by searching for lionfish and their invasion specifically, but some came searches looking for specific information. While there is data to support all control methods they were largely hypothesized through personal observation. Personal experiences in fishing and hunting revealed the first three plausible methods, while the genetic alteration method was initially suggested in a class lecture by Dr. Nicholas Funicelli in addition to seeing similar methods used on mosquitoes on local and national news outlets.
Results
My review of the literature uncovered numerous potential approaches to controlling invasive wildlife populations. While there many options available, four were chosen based on their ability to be applied in this environment. The first two options are already being implemented in this environment on one scale or another. Obviously natural predation will occur at some level, and the state has worked to push the active capture narrative. Both have been proven to be at least somewhat effective when properly implemented (DeLeon et. al. 2013)(Diler et al. 2014). The two other methods are both a bit less feasible, but could both be realistic in the future if thorough research was done prior to their implementation. The genetic alteration method has been proven in mosquitoes, but the scenario was very different than the application with lionfish (La croix et. al.2012). The introduction of natural predators is a method that has already proven to be effective in the state of Florida, but this method also offers the largest variables for possible negative repercussions (Hill 2003).
Natural predation consists of letting natural predators consume lionfish as they would any other natural prey. While this is a relatively passive control approach, we know that lionfish are predated by other species (e.g., grouper; see Albins and Hixon 2013), and this method could be effective if the proper limits are put in place to protect the larger predatory species However, it is still uncertain whether natural predation will be effective for controlling lionfish. Mumbly et al. (2011) present quantitative results supporting their hypothesis that the amount of large grouper on a reef had a direct negative effect on the populations in that area. When graphed it showed a direct linear correlation that the more large bodied groupers were present in one of their experimentation sites, the less lionfish occupied the same areas. In contrast, a follow-up study (Hackerott et al. 2013) finds evidence that predation has noticeable effects at the initial onslaught of the invasion, but in the time between the two studies the ability for these large predators to control lionfish had proven largely ineffective. The authors argued that in choosing a larger survey area they were able to limit possible localized populations where lionfish populations may have not had the opportunity to reach their maximum potential. The Diler et al. 2014 study offered interesting and related implications to this method of control. This article suggested that local fish populations could be trained to feed on lionfish overtime, by using stunned lionfish and leaving them where the fish normally feed. If more extensive research is done in an area where large bodied grouper are present, this study may prove to be an effective, though labor intensive, method of controlling some lionfish populations.
Another vertebrate that has a history of invasion, and may have some parallels is that of the nutria. Though they are terrestrial and offer a different set of challenges, there are some possible benefits that can be taken from control methods that were effective for them. In the article Bomford and O’Brien 1995 article the authors discuss the successful eradication of a nutria population, and it is compared to a study of lionfish capture in similar fashion in the de León et al. article (2013). The initial nutria invasion in Louisiana also has a fairly similar backstory to that of the lionfish in Florida. Like lionfish they were brought into the U.S. for one reason or another, and once they were able to escape and get established in the wild, their populations exploded (Nutria in Louisiana Pamphlet). While the following nutria situation was more effective than the situation in Louisiana it does lay a framework in the similarities of the issues.
In comparing Bomford and O’Brien 1995 article as well as the de León et al. 2013 study it was made clear that there is a possible way to completely eliminate the lionfish problem, but the issue may lie in the overall cost. The nutria study or eradication that was discussed in the Bomford article told of a situation where the English government spent copious amounts of money to encourage local trappers to eliminate the alien nutria populations. On page 253 they state, “Trappers received a bonus of 3 years’ salary when eradication was achieved before the deadline, so trappers were strongly motivated to trap even when few animals were caught.” de León’s results show that there is a negative relationship between fished areas and lionfish populations in their area of Curacao and Bonaire. Under this idea, if more fishing pressure is put onto lionfish the fewer lionfish there would be. If governments were able to apply the model proposed in the Bomford article this may prove to be an effective method of combating lionfish populations.
One of the primary challenges that the lionfish offers is its high birthrate or fecundity. According to Albins and Hixon a female lionfish is able to lay up to two million eggs in a year (2013). Another animal with a high birth rate is the mosquito. In the Lacroix et al. (2012) study the researchers are able to show that with genetic modification they are able to successfully reduce the populations of certain types of mosquitos. Though the challenges with lionfish are different this does offer some interesting analysis.
While the practicality of this method may receive due criticism, in an invasion of this scale all possible methods should be taken into account. The Lacroix et. al. (2012) study reveals that if mosquitos are genetically modified to sterilize the males, they will compete with the natural males, and a higher rate of female will produce infertile eggs. This study was conducted on a small scale, but it did reveal positive results. Albins and Hixon 2013 sites the rapid reproduction rate of the lionfish to be a large contributing factor in their invasion, so if researchers could identify a way to genetically sterilize lionfish, then this could become a very real alternative. It does seem like this is a fairly easier prospect when insects are concerned, but it could definitely be something worth additional research.
Lionfish are not the first invasive fish species to invade South Florida, but only the most recent in a historical trend. In the late 1980’s the state of Florida released a large amount of Peacock Cichlids (Cichla Ocellaris) in freshwater near some of the same areas where the lionfish roam today. Though this did not completely solve the invasion, it actually created another one, but it created a much more habitable situation for the native species. This is obviously not a desired remedy, but in his 2003 thesis, Jeffery Hill explores how the introduction of another top predator had effected the populations of the native top predator after an extended period of time. The author makes some basic comparisons between Peacock Cichlids and Largemouth Bass. He introduces the fact that the Cichlids were introduced by the state to reduce the population of invasive tilapia species. His hypothesis was that they would largely compete with the native largemouth for forage and resources, but he was not able to discover much statistical evidence that pointed to this. In this situation the lionfish could be compared to the tilapia species. If one of their predators from the indo-pacific was introduced it may have a limited effect on the existing ecosystem. With this comes quite a few variables that most people would not likely accept, but it is something to consider in controlling lionfish.
Discussion
My review of the literature highlights several potentially feasible methods for controlling invasive lionfish, and the uncertainty that remains in their management and control. While thorough research has been done within similar areas, we lack specific studies that test these management techniques on a large scale. The articles that are brought forward in this study all bring up very valid points, but it makes specific data comparisons difficult. If more quantitative data was available it may have been possible to more useful data in addition to eliminating possible looming questions.
As far as policy implications are concerned, the first method proposed still lacks sufficient data to prove the point one way or another. While the three studies mentioned all have valid points, they lack practicality when it comes to management techniques and consensus when it comes to results. Now that more time has passed since the initial invasion it may be prudent to conduct a third experiment that is similar to the first two. Once a scientific consensus has been reached, we can then go forward in making actual policy changes. As far as policy is concerned, if this third study does not show that grouper are a reliable ally in the fight against lionfish, then that idea could be abandoned as a possible management technique.
The second method shows that it has the ability to be extremely effective, but additional studies would have to be done to investigate what the cost would entail. With the spread of lionfish having reached its current level it would take the financial support of multiple governments, many of which lack the ability to provide enough funding to motivate the citizens to eradicate an invasion of this level. Both examples together provide hope that trapping and fishing in extreme circumstances can be effective as long as enough financial backing is put into the policy.
The third method discussed seems too uncertain to merit significant consideration at this point, but it is a hopeful idea none the less. Like the previously discussed method it would take considerable financial backing, but we have economic valuation techniques. With these techniques in place we may be able to determine that the losses created by the lionfish may even cause a long term financial loss than this sort of research would cost. There is also the ethical implications that go along with introducing genetically modified animals into the wild, but being as this is already an invasive species they seem less relevant.
The last method also lacks the quantitative data that the study was initially looking for. A study that showed the amount of tilapia before the introduction of the peacock bass and after was desired, but with the limited resources available a study that showed the neutral relationship between peacock bass and largemouth bass brings up an interesting point. If we were to introduce native lionfish predators to control populations could it be done in a way that would not make any major impact on current populations? Obviously the marine environment is far more dynamic, but this information definitely brings support for another possible control method, as unrealistic ass it may seem to be. It may also be argued that this method and the natural predation method could be combined into one method, but for the possible ecological impact that could be caused by introducing additional predatory species, this does not seem to make sense. This issue is far too extensive to merit this type of amalgamation. If natural predators are given more strict fishing limits, or trained to feed more directly on lionfish there is no real threat that could be caused to the natural ecosystem that does not already exist. If outside predators are introduced it may be effective at controlling lionfish and the fish may live in harmony, as the Hill Dissertation shows has been done with Peacock Bass in South Florida, but with the introduction of other outside species there is also a much higher risk of unintended consequences that could possibly occur.
While this study did manage to identify, explain and discuss four arguably feasible lionfish management and eradication techniques, it ended with discussion. While synthesizing the literature and research of others can be a powerful research tool, there is sometimes no substitute for real field research. In many ways this study is more of a research proposition than a study in itself. With the available time and resources multiple studies could be done doing further research on each of these proposed methods. While some are more likely to occur than others, until physical experiments can be done we will never know which would actually be the most effective and least ecologically taxing method.
Conclusion
In the end, this study should not be thought of a complete scientific work, but a call to arms to the biologists, fisherman and policy makers of Florida. Now that the issues have been identified and the solutions have been discussed, it is time for someone with the available resources to begin testing these methods in the field. While some of the provided options may seem more realistic than others, at this point all avenues still have the possibility to come to fruition. While other invasive species will continue to cost the country billions, Florida has the opportunity to take action on this situation now (Morris and Whitfield 2009). While we may never be able to successfully eradicate this species, leaving it unchecked could have dire consequences on dozens of fish species that call the reefs of Florida and the Caribbean home (Albins and Hixon 2011).
Works Cited
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Bomford, Mary, and Peter O’Brien. “Eradication or Control for Vertebrate Pests?” Wildlife Society Bulletin 23.2 (1995): 249-55. JSTOR. Web. 21 Mar. 2015.
De León, Ramón, Kin Vane, Paulo Bertuol, Valérie C. Chamberland, Fernando Simal, Eseld Imms, and Mark J. A. Vermeij. “Effectiveness of Lionfish Removal Efforts in the Southern Caribbean.” ENDANGERED SPECIES RESEARCH 22.175-182 (2013): 175-82. Web. 21 Mar. 2015.
Diller, Jessica L., Thomas K. Frazer, and Charles A. Jacoby. “Coping with the Lionfish Invasion: Evidence That Naïve, Native Predators Can Learn to Help.” Journal of Experimental Marine Biology and Ecology 455 (n.d.): 45-49. Science Direct. Web. 21 Mar. 2015.
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Morris, J.A., Jr., and P.E. Whitfield. 2009. Biology, Ecology, Control and Managementof the Invasive Indo-Pacific Lionfish: An Updated Integrated Assessment. NOAATechnical Memorandum NOS NCCOS 99. 57 pp.
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Nutria in Louisiana. Baton Rouge, La.?: Sea Grant Louisiana, 2004. Nutria.com. Louisiana Department of Wildlife and Fisheries. Web. 23 Jan. 2015. <http://nutria.com/uploads/0232.brochurerev.pdf>.
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