Sneaky Predators

By Arina Favilla, SRC intern

“Everything you see exists together in a delicate balance, ” Mufasa wisely tells Simba in The Lion King right before a pouncing lesson. This is true of any ecosystem on the planet—the sun provides energy for plants to grow, plants are grazed on by herbivores, who are eaten by consumers, who are prey to other predators. Any prey-predator imbalance can have cascading effects on the entire ecosystem, particularly when invasive predators are especially sneaky predators, beating Simba in the element of surprise.

The element of surprise is difficult to accomplish in the aquatic environment because there are several cues (smell, sight, vibrations) that warn prey of a nearby predator and illicit a fast-start response, allowing them to get as far away as quickly as possible. It is debated whether this fast-start response is an autonomic response, similar to a knee-jerk reflex, or whether an individual can optimize their escape response in accordance to the threat.

Image of the red lionfish (Pterois volitans) displaying its characteristic fins and venomous spines. (From Wikimedia Commons)

Image of the red lionfish (Pterois volitans) displaying its characteristic fins and venomous spines. (From Wikimedia Commons)

McCormick and Allan (2016) investigated the red lionfish’s (Pterois volitans) success as a predator by determining the response of prey. The red lionfish, native to the Pacific Ocean, is a threatening invasive species in the Caribbean because of their success as predators easily devouring 8-10% of their body weight each day. They quickly decimate reef fish populations and destroy the delicate balance of a reef ecosystem. Moreover, recent research suggests lionfish are successful, sneaky predators by avoiding associative learning, a survival mechanism that allows prey to associate cues with dangerous predators leading to effective fast-start responses and successful escapes.

The study compared the response of whitetail damselfish to two predators, the red lionfish and the common rockcod, as well as a non-predator fish, the three-lined butterflyfish. First, the damselfish were conditioned to associate potential risk with the sight and odor of the two predator species coupled with chemical alarm cues. Previous studies have shown tropical fish species, including damselfish, can quickly learn to associate cues of a predator as a threat. Damselfish were then exposed to olfactory cues (seawater from the predator or non-predator tank) and/or visual cues (predator or non-predator tank placed adjacent to the damselfish tank) before being startled by a stimulus (release of a metal weight at the water’s surface) to provoke the fast-start response.

Comparison of the different aspects of the damselfish’s fast-start response when forewarned through chemical (white), visual (light grey), or a combination of cues (dark grey) of either one of two predators (red lionfish or rockcod), a non-predator (butterflyfish), or controls. The optimal fast-start response would have a short response latency time, high average response speed and maximum speed, and large distance travelled. Damselfish exposed to controls had the lowest response while those exposed to the rockcod had the highest response. Both the butterflyfish and lionfish elicited similar intermediate responses. (McCormick and Allan 2016)

Comparison of the different aspects of the damselfish’s fast-start response when forewarned through chemical (white), visual (light grey), or a combination of cues (dark grey) of either one of two predators (red lionfish or rockcod), a non-predator (butterflyfish), or controls. The optimal fast-start response would have a short response latency time, high average response speed and maximum speed, and large distance travelled. Damselfish exposed to controls had the lowest response while those exposed to the rockcod had the highest response. Both the butterflyfish and lionfish elicited similar intermediate responses. (McCormick and Allan 2016)

McCormick and Allan (2016) found that the damselfish had greater fast-start responses when forewarned about the predatory rockcod through olfactory or visual cues, but showed similar ineffective fast-start responses—slow to react and slower speeds—when exposed to the cues for the lionfish as well as the non-predator butterflyfish and controls (Figure 2). In other words, the damselfish misidentify the lionfish as a non-predator, reducing its chance of escape if attacked. These results suggest that lionfish are capable of circumventing associative learning, leading to higher success rates in attacking prey. The findings of this study begin to explain the success of lionfish as predators, but further studies are required to better understand the mechanisms lionfish use to avoid forewarning of prey.

Works cited

McCormick, M. I. and B. J. M. Allan. 2016. Lionfish misidentification circumvents an optimized escape response by prey. Conservation Physiology 4:1–9.

Observing Invasive Lionfish Larval Dispersal Through Ocean Currents May Help to Reduce Population Size

By Dana Tricarico, RJD Intern

The waters of the Caribbean, Western Atlantic and Gulf of Mexico have become a hub for the invasive species called Pterois volitans and Pterois miles, more commonly known as species of Indo-Pacific lionfish. This predatory species is now an increased problem, creating negative ecological consequences to its non-native regions since 1992, when Hurricane Andrew knocked several lionfish into the waters of South Florida. According to National Geographic, they are now one of the most destructive invasive species in the Western Hemisphere and have become the first truly invasive marine fishes in the Atlantic (Albins and Mark, 2013). Since then, researchers like Dr. Matthew Johnston and Dr. Sam Purkis have been seeking ways to help manage the overabundance of this species. One major reason for the effort from scientists is due to the fact that lionfish have the potential to outcompete and prey on a large array of different types of species from all areas they inhabit. This implies that the more these species reproduce, the greater the decline of other fish recruitment, i.e. the amount of fish that survive to be added to a population (Albins and Mark, 2013).

The Indo-Pacific Lionfish is an invasive species to the Gulf of Mexico, Caribbean and East Coast of the United States. (Source:

The Indo-Pacific Lionfish is an invasive species to the Gulf of Mexico, Caribbean and East Coast of the United States. (Source:

At this point, it is no secret that lionfish are taking over. It is also apparent to many that consistent removal efforts are required as frequently as possible in order to try and manage the populations. This becomes more of a priority because, in addition to being ravenous predators, their reproduction rate is extremely high. In fact, one female lionfish can produce over two million eggs per year (Spencer, 2015).

Such a high frequency of spawning, with no indication as to when the next spawning period will be, leads to major complications in how to move forward in the eradication efforts. However, new research shows that there may be a way to combat issues associated with this. At this point, lionfish control is usually administered through “culls” either through local lionfish derbies, or by recreational spear or net fishing. Unfortunately, reducing the overall lionfish numbers in the invaded areas is usually unsuccessful with only these localized and sporadic derby events, which typically focus on adult fish in shallow water. The motivation of the study was to determine if local lionfish control such as those previously listed, in addition to increased removal efforts at many other locations with high larval connectivity, can help decrease lionfish biomass in downstream currents. In other words, this study wanted to look at areas where lionfish larval dispersal from one population to another was the strongest, and whether or not that could help in reducing lionfish populations (Johnston and Purkis, 2015a).

The Carolinas were chosen as the focus area for this study because dense lionfish populations had been found there from lionfish recruits, which traveled from locations like Cuba, the east coast of Florida, the Florida Keys, and other areas in which the Gulf Stream current passes through. Ten spawning areas were looked at in order to note where the lionfish from these locations eventually settled. A biophysical computer model was used in this study in order to look at the sites. This model took into consideration ocean climate data, ocean currents as well as life-history traits of lionfish to dictate the eventual settlement location of the lionfish. In addition to this model, previous research by Johnston and Purkis (2015a) showed that not only do the currents affect the dispersal of lionfish downstream of the Gulf Stream, but also hurricanes and other tropical storms can accelerate the spread of the lionfish as well due to a change in the flow of the water after these natural disasters. This is likely why the spread of lionfish was so quick after Hurricane Andrew hit the South Florida area (Johnston and Purkis, 2015b).

Ciruclation Patterns

The circulation pattern of ocean currents in the Caribbean, Gulf of Mexico and western Atlantic indicated by arrows.

Through the computer models, it was apparent how complex the linkages were between the study areas, and it was clear that there was a south-to-north flow of larvae, ending in the Carolinas. Johnston and Purkis estimated that regular removal of at least 20% of the population per month in heavily populated areas of lionfish, in addition to 20% of culling in regions upstream of large ocean currents, would be needed to effectively reduce lionfish numbers. These numbers also need to include all ages and sizes of fish, unlike the pattern typically seen in local lionfish derbies. The Caribbean, United States, Mexico, Central, and South America should all be targeted regions. The simulations also showed that Cuba exported lionfish to eight of the ten studied areas, so a significant amount of culling in both northern and southern Cuba would help in the great decline of lionfish (Johnston and Purkis, 2015a).

This study is significant to those trying to stop the ongoing invasion because it demonstrates the extreme need to introduce a more coordinated and prolonged international cooperation between nations linked via ocean currents and affected by increased lionfish populations. As Johnston states, “We’re all connected by water flow. That means one area that has uncontrolled lionfish populations can dramatically increased lionfish numbers in nations downstream (Nova Southeastern University, 2015).”



Albins Mark A., and Mark A. Hixon. Invasive Indo-Pacific lionfish Pterois volitans reduce   recruitment of Atlantic coral-reef fishes.” Marine Ecology Progressive Series 367:233–238 (2013).

Johnston, Matthew W., and Sam J. Purkis. “A Coordinated and Sustained International Strategy Is Required to Turn the Tide on the Atlantic Lionfish Invasion.” Marine Ecology Progress Series Mar. Ecol. Prog. Seri. 533 (2015a): 219-35.

Johnston, Matthew W., and Sam J. Purkis. “Hurricanes Accelerated the Florida-Bahamas Lionfish Invasion.” Glob Change Biol Global Change Biology 21.6 (2015b): 2249-260.

Nova Southeastern University. “More strategic culling needed to reduce lionfish invasion, researchers find.” ScienceNews. ScienceDaily, 11 August 2015.

Spencer, Erin. “Fighting Back Lionfish for Invasive Species Awareness Week.” Voices Explorer Journal. National Geographic, 24 Feb. 2015. Web. 22 Mar. 2015.


The Consequences of the Indo-Pacific Lionfish invasion into Atlantic Waters

by Laurel Zaima, RJD intern

The introduction of an invasive species into a foreign ecosystem has dire and often unforeseen consequences. An invasive species is considered any living organism that is not native to the ecosystem and causes harm to the local environment (“Invasive Species”). Non-native organisms alter the ecosystem, which affects the native species, habitat structures, human health, and even our economy. Invasive species are actually one of the leading threats to native wildlife and are the primary risk to approximately 42% of threatened or endangered species (“Invasive Species”). The inevitable alteration to the ecosystem from the invasive species causes commercial, agricultural, and recreational activities to suffer. The current invasion of the lionfish is an extremely disconcerting issue that has been damaging and disrupting the native species and the balance of the ecosystem.

Picture 2

Lionfish are originally from the Indo-Pacific and Red Sea, but they have recently invaded Atlantic waters near Florida and the Caribbean and into the Gulf of Mexico (“Lionfish- Pterois volitans”). Lionfish were some of the most commonly imported tropical fish for aquariums; however, owners would often release them into the Atlantic when they grew too large for their aquariums (“Venomous Lionfish”). Lionfish were first reported off Florida’s Atlantic Coast near Dania Beach in 1985, and since then the lionfish populations have exponentially increased and spread (“Lionfish- Pterois volitans”). [Picture 1: In the summer of 2001, this lionfish was found about 40 miles off the coast of North Carolina.]

Lionfish have an extremely high success rate for a variety of reasons. Since the lionfish are not natively found in the Atlantic waters, they have no natural predators in this region to control their populations. Lionfish have 18 venomous spines that are used as a defense mechanism (“Lionfish- Pterois volitans”). Any native predators that have unknowingly tried to consume this new food source has fallen victim to their venomous spines. The lionfish also breed at a very rapid pace because both males and females sexually mature in less than a year and have the ability to spawn 12,000 to 15,000 eggs every four days in warm climates (“Lionfish- Pterois volitans”). Lionfish have quickly spread their populations throughout the Atlantic because are tolerant to a variety of habitat conditions. They have been found in shallow waters and in depths up to 1,000 feet; they can withstand temperatures as cold as 48 to 50 degrees; and they can survive in low salinities for short periods of time (“Lionfish- Pterois volitans”). Lionfish have easily assimilated into Atlantic waters, but the main concern about the lionfish is their broad diet that negatively impacted the native ecosystem.
Lionfish hurt the wellbeing of coral reefs because of their massive predation of native species, and they compete with the native predators for food. As a predatory reef fish, lionfish are known to prey on more than 70 marine and invertebrate species including yellowtail snapper, Nassau grouper, parrotfish, banded coral shrimp, and cleaner species (“Lionfish- Pterois volitans”). These feeding habits drastically reduce the native populations in coral reefs, which result in negative effects on the reef habitat. Some of the species targeted by the lionfish play important ecological roles in limiting the amount of algae on the reefs, and without their presence, the coral reefs can be overgrown by algae (“Lionfish- Pterois volitans”). Lionfish often target the native juvenile species as another source of food. Albins and Hixon (2008) found that lionfish caused significant reductions in the recruitment of native fish by an average of 79% over a 5-week study period. Targeting the coral-reef fish at the early stages of life declines the abundance and diversity of the local fish (Albins and Hixon, 2008). Complete eradication of lionfish from the Atlantic and Gulf of Mexico is probably unobtainable; however, efforts need to be made in order to control their rapidly growing populations.
There are a couple solutions that can be implemented towards the extermination of the invasion of lionfish. The first step that must be taken is to educate the public about lionfish in the Atlantic and Gulf of Mexico and the damaging effects they have on the natural ecosystem. Local fishermen should be encouraged to remove any lionfish that they catch to help limit the negative impact this species has on the native marine life (“Lionfish- Pterois volitans”). Commercial fisheries and recreational fishermen should also be encouraged to target lionfish as a main catch (Hixon, Albins, Redinger, 2009). When filleted and cooked properly, lionfish are very delicious. This species could be profitable to fisheries if they target to catch and sell them as a form of sustainable seafood. The recovery and maintenance of healthy populations of native predators, such as large grouper and sharks, can help regulate lionfish populations as well (Hixon, Albins, Redinger, 2009). Lionfish population controls can be regulated on a regional and nation wide level. Regions need to ensure that they are prioritizing the removal of lionfish from key areas such as marine protected areas (MPAs), high tourist areas, spawning aggregation sites, and nursery areas (Akins, 2012). These regions are extremely vulnerable to the lionfish, and an invasion by these predators could be detrimental to the recruitment and survival of local reef fish. A nation wide control effort of the lionfish in the Atlantic could help to reduce the lionfish in mass quantities (Akins, 2012). However, in order to monitor the progress of the nation’s control plan, commercial and recreational fishermen and scientists need to continue to report and document the lionfish caught in order to gauge the effectiveness of the implemented programs (Akins, 2012). [Picture 2: A Virgin Islands biological technician examines the Indo-Pacific lionfish captured off the coast.] By enacting some of these invasion control plans, the lionfish population can be better regulated, and the coral reefs and native species would be better preserved.
Works Cited
Akins JL (2012) Control Strategies: Tools and Techniques for Local Control. Pages 24-47 in: JA Morris Jr. (ed.) Invasive Lionfish: A Guide to Control and Management. Gulf and Caribbean Fisheries Institute Special Publication Series Number 1, Marathon, Florida USA. 113 pp.
Albins MA, Hixon MA (2008) Invasive Indo-Pacific lionfish Pterois volitans reduce recruitment of Atlantic coral-reef fishes. Mar Ecol Prog Ser 367: 233-238.
Hixon M, Albins M, Redinger T. “Lionfish Invasion: Super Predator Threatens Caribbean Coral Reefs.” NOAA’S Undersea Research Program. NOAA, 8 Mar. 2009. Web. 4 Feb. 2015.
“Invasive Species.” National Wildlife Federation. n.p. n.d. Web. 4 Feb. 2015.
“Lionfish- Pterois volitans.” Florida Fish and Wildlife Conservation Commission. n.p. n.d. Web. 4 Feb. 2015.
“Venomous Lionfish Invade South Florida Waters.” n.p. 2010. Web. 4 Feb. 2015.

Summary of “Competitive interactions for shelter between invasive Pacific red lionfish and native Nassau grouper”

Hannah Armstrong, RJD Intern

Invasive species have the potential to negatively effect normal ecological function in any environment. Marine biological invasions are increasingly common, most notably that of the Pacific red lionfish (Pterois volitans).  While the lionfish invasion and its direct effects on native fish communities has been well researched, there has been little documented evidence regarding non-predatory interactions.  In a 2014 study by Raymond, Albins and Pusack, they observed whether Pacific red lionfish and Nassau grouper, two species that occupy similar habitats, compete for shelter and whether or not the competition is size-dependent.

Pacific red lionfish (Pterois volitans) have been reported in the Atlantic Ocean since the mid-1980s and now pose a threat to the western Atlantic and Caribbean coral reef systems.  As small-bodied predators, they are capable of significantly reducing the abundance and diversity of native fishes via predation. Nassau groupers (Epinephelus striatus), despite being regionally endangered, are a larger predator found throughout the lionfish’s invasive range. Because these two species use similar resources and compete for similar habitats, it is important to understand how they interact and what may result from their competition.


The invasive Pacific red lionfish, Pterois volitans. (Source: Smithsonian Marine Station at Fort Pierce)

In order to investigate how Pacific red lionfish and Nassau grouper affect each other’s behavior, the three scientists set up an experiment to compare their distance from and use of shelter when in isolation versus when both species were in the presence of each other with limited shelter. The two species were first held in separate cages with partitions to allow for isolation periods lasting 24 hours, and interaction periods lasting 48 hours, with each cage containing a shelter that the scientists constructed. The trials were based on size-ratio treatments: first they observed similarly sized lionfish and Nassau grouper, then they observed a juvenile lionfish and a substantially larger juvenile Nassau grouper, and lastly they observed an adult lionfish and a much smaller juvenile grouper. Finally, to test for predation between the two species, they incorporated a prey fish in some of the trials.


The native Nassau grouper, Epinephelus striatus. (Source: IUCN Red List)

Upon statistical analyses, Raymond, Albins and Pusack eventually came to two conclusions regarding the interactions between these two species, and specifically Nassau grouper avoidance behavior: first, they found that when Nassau grouper interacted with smaller lionfish, they avoided them by moving further from the shelter occupied by lionfish, and by using the shelter less often, and second, they found that when Nassau grouper interacted with similarly sized lionfish, they avoided them by increasing their proportion of shelter use, and by avoiding the part of the experimental cage where lionfish were consistently present. The scientists ultimately found that the Nassau grouper significantly changed position relative to shelter in the presence of lionfish, however the lionfish did not change their positioning upon interacting with the Nassau grouper. This demonstrates how they have a tendency to compete for limited shelter, and the manner in which the Nassau grouper avoid lionfish is size-dependent.

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Configuration of experimental cages used in this study.

While this study highlights the competitive interactions for shelter between invasive Pacific red lionfish and Nassau grouper, it is important to note that it was performed in a laboratory setting.  For future conservation efforts, it will be critical to consider how this might apply in a natural reef habitat, and whether or not this competition could lead to lionfish being a dominant predator rather than the native Nassau grouper, a shift that may result in trophic cascades.



Raymond, WW, Albins MA, Pusack TJ.  Competitive interactions for shelter between invasive Pacific red lionfish and native Nassau grouper. Environ Biol Fish (2015) 98:57-65. 31 January 2014.


Dietary preferences of lionfish in the United States

by Audra Burchfield,
Marine conservation student

Imagine being a reef fish around twenty years ago. You are swimming around when all of the sudden a new fish you have never seen before is on the reef. Over the next few years more of these strange fish are present and pretty soon they are common place. The reef has been invaded by an alien.

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