Read an updated version of this article published February 2017: Eradicating Lionfish

Unfortunate accidents in the early 90's have led to their invasion and spread across much of the Caribbean Sea and as far north up the east coast to Rhode Island. Although, they do not live long in our cooler waters and are unable to survive the tougher winters (Kimball et al. 2004).

Lionfish in the Atlantic are termed invasive species: a non-native organism that has intruded into an area and may have serious detrimental effects on native organisms, the local economy and human health. One of the most infamous cases is in invasion of the Great Lakes in 1988 by non-native zebra mussels (Dreissena polymorpha). These have caused severe problems at power plants by blocking pipes and also wiped out the native clam population.

The majority of alien invasions result from human activities and the globalization of the world market. According to some estimations the major environmental damages, losses, and control measures for invasive species cost the U.S. an average of $138 billion per year and invasive species also threaten nearly half of the species currently protected under the Endangered Species Act (NOAA).

How did the lionfish end up in US waters in the first place?

It is speculated that the root of the problem was only 6 lionfish accidently released from an aquarium during hurricane Andrew in 1992. Genetic research supports this finger pointing but it is likely that many more have been intentionally released by "retired" aquarium enthusiasts. With no natural enemies and an extremely high reproductive rate of 2 million eggs a year from one female, unsurprisingly they've taken over rapidly (NOAA).

The cold water temperatures are keeping their numbers in check to the north, but this is not the case to the south where lionfish are spreading rapidly through the South Florida Estuaries, the Gulf of Mexico and the Caribbean Sea. Marine Scientists believe they will have established themselves as far south as Brazil within the next five to ten years.

Surveys conducted by Paula Whitfield and her team in 2004 found that lionfish were already as abundant as many native groupers, and second in abundance only to scamp (Mycteroperca phenax) (Whitfield et al, 2007). This is extremely concerning given the short time period for this population growth to occur. Recent estimates of lionfish densities show the populations continuing to grow, with the highest estimates reporting over 1,000 lionfish per acre in some locations (NOAA).

Lionfish now occupy an extensive geographic range, and are able to survive in a range of habitats and depths (2-140m). Lionfishes have now become established in Bermuda, the Bahamas, Columbia, Cuba, the Dominican Republic, Jamaica, Puerto Rico, Turks and Caicos, and the Cayman Islands. There are also reported sightings in Belize, Haiti, U.S. Virgin Islands, Mexico, and Aruba, Curacao, and Bonaire (NOAA).

Why is this bad?

Lionfish are voracious predators and are taking the already threatened Caribbean reefs by storm. Lionfish are non-selective feeders, and with virtually no natural enemies in the tropical western Atlantic they've invited themselves to an all you can eat seafood buffet. Lionfish have been observed consuming 20 small fish in a 30-minute period and prey up to 2/3rd of their own length. Impressively, their stomachs can expand up to 30 times their normal size after a meal. Mark Hixon et al (2009) determined that a single lionfish can reduce juvenile fish populations by 79% in just 5 weeks.

Samples of lionfish stomach contents in the western Atlantic have shown that they consume more than 50 different species, many of which are overfished and diminished to already critical levels (Gupta, 2009). Given this extreme rate of feeding lionfish are out-competing native predators for their food sources, as well as reducing fish populations through direct predation.

Not only are they dangerous to the fragile ecosystems, but they can inflict an extremely painful sting to humans, not usually deadly, but it can make you quite sick.

Are there any solutions?

Due to the extent of the lionfish invasion, control is now the only option as attempts to eradicate existing lionfish populations would be impractical and probably unsuccessful (NOAA).

In the Pacific groupers, sharks and coronetfishes are known to prey on lionfish. In the Atlantic, groupers are severely overfished and struggling to fill this role. The first documented case of grouper predation was in the Bahamas in 2008, when several groupers were captured containing partially digested lionfish remains in their stomach (Maljkovic, 2008). For this, and many other reasons, predator populations need to be protected and allowed to recover.

Another method of control is something that humans are notoriously good at - let's eat them! Apparently lionfish are tasty, with light, white and flakey meat, and have been received very well in some high end New York, Washington and Chicago restaurants following the success of Bermuda's Eat 'Em to Beat 'Em , campaign. Scientists from Roger Williams University, REEF, NOAA and the North Carolina Sea Grant (Morris et al, 2011) have just published a study detailing the nutritional benefits of lionfish consumption; lionfish have the highest concentration of omega-3 in their category, scoring above farmed tilapia, Bluefin tuna, red snapper and grouper. Claimed to be the "ultimate in guilt-free eating - delicious, nutritious and eco-conscious". Lionfish is certainly in the ocean friendly seafood choice list. How about some fluffy battered lionfish, lionfish sushi or lionfish fingers?

Perhaps a more unique approach is being tried out by divers in Honduras who are trying to train local sharks to eat the invasive lionfish (National Geographic).

At the current rate of population growth, these measures are unlikely to be able to restore the ecosystem balance, but it is hoped it may perhaps slow the spread and buy a little more time for a solution.