Red Lionfish, Pterois volitans, the Voracious Invasive Species
This topic submitted by Eleanor Comiskey at 2:34 PM on 5/16/09.
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The Red Lionfish, or Pterois volitans, is a venomous tropical fish that have distinctive red, maroon, or brown and white stripes. They have a fan-like pectoral fin and many dorsal spines along their body, all of which are venomous and can cause great pain to any human who is stung. Adult lionfish can grow up to 17 inches long. These fish are voracious predators and are generally on the top tier of the food chain in their habitat, which typically includes lagoon and seaward reefs in depths over 50 meters. These fish Òoccur naturally throughout the western Pacific Ocean from southern Japan and southern Korea to the east coast of Australia, Indonesia, Micronesia and French Polynesia and in the South Pacific Ocean from western Australia to the Marquesas and Oeno in the Pitcairn IslandsÓ (Ruiz-Carus, Matheson, Roberts, & Whitfield, 2006). If these fish are located naturally in these Pacific Ocean waters, then how and why have they established themselves in the Atlantic waters along the Eastern coast of the United Sates and in the Bahamas?
The Red lionfish is an invasive species in these waters. Invasive species are Òa species that is not native to a particular ecosystemÓ and are Òreferred to as alien, exotic, or non-indigenousÓ (Ericson, 2005) to that area. Invasive species are generally harmful to the area in which they have been introduced, and will cause harm biologically, economically, or to humans themselves. Invasive species introduced to an environment by humans are called species introductions. This practice of introducing new species is not at all new in our history. For many years, humans have introduced species on accident, such as stowaways on boats traveling overseas to other lands, as well as on purpose. Humans have purposely introduced species to new environments to satisfy their demand for food and social needs (Smith & Sealy, 2007). However, today the introduction of species into new areas has increased dramatically due to the high demands of luxury items and overseas trade between nations. Today, the causes of the introduction of these invasive species are far and wide, and according to Ericson (2005), some of the reasons include a combination of economic activities with Òthe rapid expansion of international trade, travel, and transportÓ.
Any type of invasive species, not just the Red Lionfish, Òcan harm fisheries, introduce parasites and endanger native speciesÓ (Avasthi, 2004). They can also Òthreaten biodiversity, habitat quality, and ecosystem function and are now considered among the greatest threats to native species in the United StatesÓ (Ericson, 2005). Lionfish are one of the most valuable marine fish transported to the U.S., which plays a large part in the introduction and establishment of the species into our waters. After the introduction of this fish into the area, the Lionfish most likely continued to establish itself with the help of more introduced Lionfish through trade and the releasing of the animals into the ocean purposely by humans. The introduction of the Lionfish and other non-native marine species has led to many consequences for the coral reefs, in fact, Òinvasions by introduced (alien) species have been ranked among the most potential perturbations of marine ecosystems and alteration of habitats and food webs by invasive species has been proposed as a major factor in degradation of coral reefsÓ (Bruckner, Coles, Dodge, Renaud, & Riegl, 2009).
According to many sources, the Lionfish first established itself in Bascayne Bay, FL in 1992 after Hurricane Andrew destroyed a home aquarium that contained six Red Lionfish, all of which escaped into the Atlantic Ocean. However, it has also been reported that these fish have been in the Atlantic as early as 1980, when home aquarium owners dumped their fish into the sea or when pet shop owners purposely dump fish into the ocean in order to establish a population for their customers upon their demand. Since the hurricane, however, the fish have quickly established themselves in the Florida waters and have spread all the way north as New York, where juvenile Lionfish have been found (Meister, Wyanski, Loefer, Ross, Quattrini, & Sulak, 2005). The fish have also spread out to the Bahamas and Bermuda.
It is not completely clear how the invasive species have traveled so far north and have established themselves in these waters so quickly, but it is clear that they are persistent in their spreading and are easily able to take over many different areas that experience different kinds of weather. Not only are these creatures able to establish themselves in many areas, they are also able to become Òwidespread in reef habitats throughout the southeastÓ (Meister, Wyanski, Loefer, Ross, Quattrini, & Sulak, 2005), taking over many reef habitats, which shows that their impact on other populations on the reef is extremely significant.
As stated before, the Lionfish are voracious predators, typically at the top of the food chain in their natural environment. They usually prey on a variety of fish, shrimp and crabs. The Red Lionfish are Òopportunistic predatorsÓ that use many different hunting techniques in order to be most successful. Some of these techniques include: hunting at dusk, which makes those prey that are diurnally active more vulnerable and easier to obtain; hunting in small groups in order to maximize the amount of prey caught; and using their pectoral fin to flush out and obtain prey such as shrimp and amphipods by vibrating the fin rays over the reef surface. By using all of these techniques, the Lionfish are capable of obtaining as much prey as they need and are also able to establish themselves in new habitats as one of the larger threats in many reef environments and other areas that they have spread throughout.
Not only are these fish aggressive hunters, but they also begin to hunt at a very young age and grow very quickly, becoming too large for any fish to eat. However, even at a small size, the fish are still not appetizing to other fish due to their highly toxic dorsal spines that mechanically release toxins when pressure is put on the spine. These fish are proving to have a selective advantage over many of the native fish of the U.S. reefs, even though they just recently established themselves in the environment (Raloff, 2006). The Lionfish that have invaded new waters are also adapting to their new environment by changing some of their hunting habits and are Òdeveloping into daytime hunters in the Bahamas, whereas they're largely nocturnal in the Indo-Pacific Éand not just coral-reef predatorsÓ (Whitty, 2009). Due to the fact that the fish are changing the way they hunt in these new waters, they have been able to spread far and wide and continue to destroy fish populations as they move because the native fish have never interacted with this predator before.
In order for a habitat to thrive, different relationships are established between animals and plants in order for all species to co-exist in the environment. There is a food chain that sets up the eating habits and controls the amount of fish in that area. However, when a species like Pterois volitans are introduced into this habitat, the food chain and the environment as a whole is completely changed. The Lionfish end up eating much of the food because of their various foraging approaches that I discussed. This disturbs the food chain because the Lionfish are now eating the prey for many other animals as well. When food is taken away from organisms, those organisms can be completely wiped out by either leaving that habitat to go find a new ecological niche for themselves or by dying out due to the lack of food. Also, when you have such a voracious predator such as the Lionfish, they can completely wipe out species by themselves by eating all of the organisms in a species.
According to a study done by Joseph Love and Peter Chase (2007), Òone of the most dramatic temporal changes in the North Atlantic has been the decline in the number of top predators over the past 100 years, especially shark populations. This decline can result in changes in abundance and composition of lower trophic levels or diminished diversityÓ By eating all of the lower trophic levels, the Lionfish are responsible for the decline in the numbers of fish at all levels of the food chain. As the Lionfish spread farther and farther in the Atlantic waters, they are negatively affecting more and more environments that are not used to this type of aggressive predator.
In addition to being harmful to native fish and, therefore, the habitats that the Lionfish have invaded, they are proving to be harmful to humans in ways as well. There havenÕt been any recorded deaths, however, the fish are extremely aggressive even with humans and have been known to approach divers, rather than veer away like most fish, having sometimes even lunged at the divers. The toxin released by the fish causes great pain and swelling in humans, and usually results in a trip to the hospital. Although the fish eat many different things, mostly consisting of fish, not much of their appetite coincides with what we eat. The Lionfish do not eat groupers or snappers, which are important commercial fish, however, their presence and ferocious appetites for the things that those fish eat affect the populations of the commercially important fish, which in turn affects our fishing and the fishing economy (Raloff, 2006).
Although it is extremely apparent in this case that invasive species can be extremely harmful to environments, not all invasive species are harmful. For example, in Mission Bay, San Diego, the invasive species, Asian Mussel, Musculista senhousia, Òcreated a new habitat by producing mats of byssal threads in the predominately unstructured mudflatsÓ of the area. This new habitat provided an environment of higher diversity and abundance of different taxa than the surrounding areas (Smith & Sealy, 2007). However, despite the fact that some, though few, invasions provide positive effects, it is hard to ignore how quickly some invasive species are spreading and taking over their new habitats. The invasion must be monitored and we must be more careful about what we let into the ocean either through trade and travel or through our own hands.
Due to the fact that this rapid bottleneck effect of Red Lionfish in the Atlantic Ocean, much work is still being done in order to find out more information about the fish and how they have come to be extremely successful in these waters, even more successful and larger than in their native waters. Research is being done to see how the fish are affecting the reef habitat, the other species that inhabit it and humans as well. The fish are a threat to be reckoned with. It is apparent that they are aggressive creatures that are capable of many things. Their expansion and growth needs to be continuously managed and observed to understand this creature better as well as to monitor its progression in hope that it does not cause more harm.
The fish has become so well established, that we are not able to eradicate it, so the only thing we can do is monitor the behavior and track where they are going. An article in The Nature Conservancy claimed that ÒPrevention is often the only viable option for combating marine invasivesÉmost of the invasives in the database would be difficult, if not impossible, to controlÓ (Bodin, 2008). In addition to this, we as humans must be much more careful about what we put in the oceans. When aquarium owners put fish into the ocean, it may not always be a bad thing, but very often fish that do not belong in that ocean or habitat, as seen with the Red Lionfish, are put into the ocean and forever change the environment that they are in. The establishment and invasion of the Red Lionfish is fascinating, yet also threatening, and deserves to be looked at and studied thoroughly.
Bibliography
Avasthi, A. (2004). Releasing Nemo proves a disaster for native fish. New Scientist , 13.
Bodin, M. (2008). Going Under. Nature Conservancy , 58 (3), 10-11.
Bruckner, A., Coles, S. L., Dodge, R. E., Renaud, P., & Riegl, B. (2009). Coral Reefs. Annals of the New York Academy of Sciences , 1162, 136-186.
Ericson, J. A. (2005). The Economic Roots of Aquatic Species Invasion. Fisheries , 30 (5), 30-33`.
Love, J. W., & Chase, P. D. (2007). Marine Fish Diversity and Composition in the Mid-Atlantic and South Atlantic Bights. Southeastern Naturalist , 6 (4), 705-714.
Meister, H., Wyanski, D. M., Loefer, J. K., Ross, S. W., Quattrini, A. M., & Sulak, K. J. (2005). Further Evidence for the Invasion and Establishment of Pterois volitans (Teleostei: Scorpaenidae) Along the Atlantic Coast of the United States. Southeastern Naturalist , 4 (2), 193-206.
Raloff, J. (2006). Bad-News Beauties. Science News , 170 (11), 168-170.
Ruiz-Carus, R., Matheson, R. E., Roberts, D. E., & Whitfield, P. E. (2006). The western Pacific red lionfish, Pterois volitans (Scorpaenidae), in Florida: Evidence for reproduction and parasitism in the first exotic marine fish established in state waters. Biological Conservation , 128 (3), 384-390.
Smith, N., & Sealy, K. S. (2007, September). The Lionfish Invasion in the Bahamas. Bahamas Naturalist & Journal of Science , 35-39.
Whitty, J. (2009). Listen to the Lionfish. Mother Jones , 34 (1), 60-65.
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