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Unwanted invaders
Lionfish in the Atlantic Ocean and Caribbean
One of the main threats to ecosystem biodiversity is the introduction of non-native (i.e. exotic or
invasive) species (see textbook p.188). Well-known examples of this are the introduction of the grey
squirrel from North America into Europe, where it has led to the reduction in population density of the
indigenous red squirrel, and the proliferation of the cane toad in Australia following its introduction in
1935 to eradicate the cane beet beetle.
Over the past decade the lionfish (Pterois volitans), a reef
fish native to the Indo-Pacific, has become increasingly
abundant in the Atlantic and Caribbean, in oceans where it
has not historically been found. Current distribution
includes the Atlantic coast of the USA, the Caribbean
coasts of Central and South America, the Gulf of Mexico,
the Greater Antilles, and the Leeward Islands. Scientists
believe that the fish escaped from aquaria in Florida into
United States coastal waters, and has since expanded in
numbers due to a lack of competition and predation, along
with abundant food supplies.
Lionfish are venomous and aggressive marine fish. They
belong to the family Scorpaenidae: the genus to which
they belong (Pterois) is characterized by red, white and
black stripes (used to put off predators by indicating
toxicity, or by breaking up body form), and elaborate
pectoral and dorsal fins. All members of the Scorpaenidae
Pterois volitans (Lionfish)
have venom glands in dorsal, anal, and pelvic spines: the
main function of these spines is to defend against
competitors and predators. Lionfish have been shown to overpopulate reef areas and force native
species to move to areas where conditions may be less favourable for them. They therefore pose a
major potential threat to reef ecological systems on the east coast of the USA and Caribbean.
Lionfish are a benthic species – feeding at the bottom layers of the reef rather than in the water
columns above (where pelagic fish feed). They suck small fish, crabs and other food off the surface of
the reef, and can use their pectoral (side) fins to trap food. The largest of lionfish can grow to about 15
inches (0.4 meters) in length, but the average is closer to 1 foot (0.3 meters).
Download a factsheet about lionfish here.
For more information on the non-indigenous aquatic species off the east coast of America see the US
Geological Survey site.
© Pearson Education Ltd 2011. For more information about the Pearson Baccalaureate series please visit
www.pearsonbacc.com
Effects of the invasive species
Lionfish have become the second most abundant species of fish from the Bahamas to North Carolina.
In the Bahamas they feed on more than 41 species of fish, including commercially valuable species like
grouper and snapper as well as fish that keep the reefs clean of algae. Pterois could have a significant
impact on prey population numbers, thereby directly affecting complex food web relationships and
having knock-on effects for many food chains. Reef deterioration and the collapse of food chains could
therefore be direct results of the lionfish invasion.
Possible solutions
Thorough and repeated removal of lionfish from invaded waters will be necessary to control their
numbers (which are currently growing exponentially). Conservation groups are organizing hunting
expeditions for Pterois, and other scientists are training reef sharks to hunt and eliminate the lionfish.
Lionfish are used extensively in cooking – they are tasty and succulent with a similar texture to
grouper. Many recipes for lionfish exist, including fried lionfish, lionfish ceviche, lionfish jerky and
grilled lionfish. Human consumption of lionfish may prove to be one of the best ways to reduce
population numbers and aim for total eradication from the invaded waters.
Tasks
1. Research and write about another example of an invasive species that has adversely affected native
biodiversity.
2.
What other factors cause a loss of biodiversity? (HINT: the mnemonic ‘H.I.P.P.O.’ helps to recall
the various threats that biodiversity faces, with each letter representing a different threat.)
3.
If you live on the eastern seaboard of the USA, the Caribbean, or other areas in its distribution
zone, keep your eyes open for lionfish. To report sightings of the fish use this report sheet.
Knowledge of the distribution of the species will be essential in planning ways of removing this
unwanted invader.
4.
If you live in an area where lionfish are commonly available, find a recipe and prepare a fish for
family or friends. Promote this fish as an alternative to other edible species and help reduce
population densities in areas where the fish are found outside their natural distribution.
© Pearson Education Ltd 2011. For more information about the Pearson Baccalaureate series please visit
www.pearsonbacc.com
Suggested answers
1. For example: red-clawed signal crayfish (Pacifastacus leniusculus), a large, aggressive American
species which has wiped out almost 95% of the native UK white-clawed species
(Austropotamobius pallipes) since it was introduced to the country in the late 1970s; human
activity has led to an increase in numbers of crown of thorns starfish which eats coral reef leading
to extensive damage (e.g. Great Barrier Reef).
2.
Habitat destruction or fragmentation; Invasive species; Pollution; Population growth (human);
Overhunting (see pages 188 and 211 of textbook).
3.
Good hunting!
4.
Some possibilities: see these recipes.
© Pearson Education Ltd 2011. For more information about the Pearson Baccalaureate series please visit
www.pearsonbacc.com