Aquatic Invasive Species

The red lionfish (Pterois volitans), popular among many aquarium enthusiasts, is a large fish native to the indo-Pacific region of the Pacific ocean. It has few predators and is able to survive in a variety of conditions, making it a formidable invasive species. Originally introduced into the Atlantic Ocean along the coast of North America, it has since damaged Bahamian ecosystems and reef systems.

Red lionfish populations in the Bahamas have been observed to be at a density of 390 lionfish/hectare, a density high than recorded even in their native habitats. Its high rate of population growth is due to a lack of any predatory fish in the Atlantic Ocean. A lack of competition has enabled these invaders to decrease Atlantic fish recruitment in the Bahamas to coral reefs by 79%.

Rui Dai of Duke University, among numerous other researchers, postulates that not all hope is lost for the Bahamian coral reefs. In 2008, several Nassau and tiger grouper (native Bahamian grouper species) were found to have lionfish remains in their stomachs. Dai is interested in whether these Bahamian grouper, perhaps with the help of humans, may be able to serve as natural biocontrol for the red lionfish.

To test her theory, Dai plans to place several groups of different proportions of the grouper, the lionfish, and other fish species native to the Bahamas in commercial fish pens, which are used while still in the ocean. This type of fish pen will be used because it should enable salinity levels, etc., in the experiment to be identical to those in the Bahamas, the environment in which the results of this study are applicable.

Each test group will contain one Bahamian grouper (of either species) and two, four, or eight lionfish, as well as a variety of crustaceans, small fish, and squid found in the Bahamas. Dai will also test the grouper at different ages (five months old, one year old, and five years old) to see whether only the largest adult grouper could be successful biocontrol agents. Each morning, Dai plans to observe which species are still present in each pen. The entire study will last approximately three months, after which point Dai expects to have enough data to draw conclusions about the approximate success of Bahamian groupers as biocontrol agents against red lionfish.

Dai expects that large numbers of the adult grouper will be the most successful biocontrol agents, though human assistance will be imperative for their success. Once Dai has obtained results from her study, she hopes that others will continue research about how to best implement Bahamian grouper as biocontrol agents against the red lionfish.

The Red lionfish – a colorful, yet poisonous tropical fish – is native to the coral reefs of the southeastern Pacific. In 1992, a hurricane damaged a Florida aquarium, and Red lionfish were released into the wild. Since then, the lionfish has spread up the Atlantic coast. Their invasion poses an ecological problem because they have very few predators, due to their dangerous venom. Researchers are unsure of the threat that this fish poses to biodiversity in its new habitat.

Traditional bio-control methods offer limited hope for containing the lionfish population because of the lionfish’s lack of predators and wide distribution throughout the Atlantic Ocean, says Frank Chang of Duke University. He is proposing a study of the lionfish’s food sources, to see how different food sources affect the growth rate of the fish. He plans to send research teams to multiple locations across the Atlantic coast, where they will monitor, catch, and analyze the stomach contents of lionfish.

The results of the study will help to elucidate why lionfish have higher growth rates in some areas, and lower growth rates in others, if they are caused by specific local lionfish diets. Chang hopes that this work will help biologists to develop a “ranking system” of areas where Red lionfish have invaded, so that control efforts can be better directed to areas that may be at higher risk of lionfish colonization.

Increasing concern over the invasive threat of the red lionfish (Pterois volitans) has become ever present. The species has been observed to have spread ubiquitously throughout the Bahamas and along the east coast of North America. They disrupt coral reef by reducing indigenous Bahamian fish recruitment by over 79%. And because of the lionfish’s poisonous fins, there have been concern about whether its growth can be contained.

Maljkovic and Leeuwen (2008) of Simon Fraser University however reported anecdotal incidences of finding native Bahamian groupers (tiger grouper, Mycteroperca tigris and five other Nassau groupers) with partially digested red lionfish in their stomaches. This provides hope that there is a potential native biocontrol for the invasion of lionfish, and that the species will be safely integrated into Bahamian ecology without significant damage to the current ecological structure. However, the anecdotal evidence in this paper still needs to be empirically confirmed.

Coral Reefs (2008) 27:501 DOI 10.1007/s00338-008-0372-9

Given the wide distribution of the Red lionfish (Pterois volitans) along the US Atlantic coast, it is unsurprising that the diet of these fish should vary with location. Different places offer different kinds of crustaceans and fishes.

Morris and Akins (National Oceanic and Atmospheric Administration) did their study in the Bahamas. During every month of a year, they routinely captured and dissected Red lionfish in order to determine stomach contents. What they found was that teleosts (fish) comprised most of the Red lionfish diet (78% volume). Crustaceans made up the majority of the remainder (14%). It was noted that larger lionfish preyed almost entirely on teleosts. These feeding habits will provide useful insight for trying to control the spread of this invader.

Environmental Biology of Fishes Volume 86: 389-398 (2009).

Environmental Biology of Fishes volume 50: 391-403 (1997).

Red Lionfish (Pterois volitans) are an invasive species of spiny fish that have invaded the US Atlantic coast for about the past fifteen years. Their voracious predation on smaller fish and lack of many predators has facilitated their rapid spread as far north as the coast of New York.

A published study suggests another possible reason for the Red Lionfish’s successful spread- its ability to last up to eight weeks without food. Red Lionfish were kept in tanks during this period and dry-weighed each week. Unlike some other species, the Red Lionfish lost less and less weight each week. Overall they lost a smaller percentage of their original body mass (10%) compared to the other species of lionfish discussed in the study. This versatility probably explains how the Red Lionfish adapted so well in Atlantic waters when it was initially released.

With their striped coats and long yet poisonous fins, Red Lionfish make an exotic aquarium specimen. However, they have recently been spotted in record numbers in the Caribbean Sea and as far up the Atlantic coast as New York. They are tenacious creatures, constantly swimming and feeding off the smaller fish that keep seaweed growth in check. They have few, if any, predators. Sharks appear to be reluctant to eat them, and although Red Lionfish move slowly, they usually swim just deep enough so that they can’t be caught using nets. In short, Red Lionfish can be extremely disruptive to the reef ecology along the Atlantic coast.

Red Lionfish were originally found in southeastern Asian waters, but it is believed that they were accidentally released into the Atlantic Ocean after a hurricane destroyed part of a Florida aquarium in the early nineties. They were spotted swimming in nearby waters a few days later. What I do not understand is why they did not initially recapture the fish when they were spotted. The aquarium officials even knew that they were only missing six fish. In any case, I think it is fascinating to see how such an exotic fish can be so adaptive in a new environment literally half a world away.

My parents used to take me to Asian farmers’ markets when I was little, and while most children press their noses on the windows of candy stores, I vividly recall pressing my nose on the glass of the seafood tanks at these farmers’ markets in Georgia. There were so many unusual creatures: squids, frogs, and sharks. I am not absolutely sure, but I think I might have also seen Red Lionfish on display in one of the tanks. I remember the same peacock-like fan of reddish brown spikes.

I think that one way to control the Red Lionfish would be to eat it. They are a delicacy in their native homeland and people in the Huffington Post article claimed that Red Lionfish taste a bit like halibut. If Americans could develop a taste for Red Lionfish, this would be a viable and not to mention delicious solution.

Frank Chang

Sources:

http://www.huffingtonpost.com/2008/08/18/red-lionfish-invade-carib_n_119521.html

http://www.shellfish.uga.edu/invasive%20webitems/Educational%20materials/Booklet%20Proof%20minus%20blank%20pages.pdf