Blue tangs, Acanthurus coeruleus, live on shallow marine reefs throughout the western Atlantic Ocean, the Gulf of Mexico, and the Caribbean Sea. Blue tangs range from New York in the north to the Amazon delta in Brazil. They are found east to Bermuda and Ascension Island but are most common in the Caribbean, and coastal Florida and the Bahamas. (Bester, 2005; Froese, et al., 2003; MarineBio.com, 2005)
Blue tangs live primarily on hard-coral reefs. They can also be found near soft corals, rubble, seagrass beds, and algal beds. Young fish prefer areas with plenty of cover. Breeding individuals congregate at flat, sandy areas between patches of reef. They shelter in coral holes and crevices. Blue tangs can be found at depths of 2 to 40 meters. (Froese, et al., 2003)
Acanthurus coeruleus reaches 39 cm in length. A sexually mature fish is typically over 10 cm in length. Adult coloration is deep blue and occasionally purple. Mature fish are able to temporarily change color between near-black and pale white. These color shifts can encompass the entire fish or portions of it and are different between the sexes. Similar to other fishes in the family Acanthuridae, Acanthurus coeruleus is a laterally compressed, pancake-shaped fish with high eyes, a subterminal mouth, yellow caudal spine at the base of the tail, and a dorsal fin that ends at the caudal peduncle. Juveniles are bright yellow. Older juveniles are blue or orange-brown with grey stripes. The sharp caudal spine is found in a horizontal groove on the peduncle and can be extended during aggressive interactions. Acanthurus coeruleus has 9 dorsal spines, 26-28 dorsal soft rays, 3 anal spines, and 24-26 anal soft rays. (Bester, 2005; Deloach, 1999; MarineBio.com, 2005)
Eggs take 24 hours to hatch. Upon hatching, the pelagic larvae are less than 2 mm in length. The young, called ""acronuri"", are transparent, silvery, and diamond-shaped. They begin to develop scales and dorsal and anal fins at 2 to 6 mm in length. The caudal spine appears when the larvae reach 13 mm in length. Older acronuri drift to nearshore areas where they meta morphose into juveniles, including losing their silver color, developing a more rounded profile, and developing an elongated snout. (Bester, 2005; MarineBio.com, 2005; Thresher, 1984)
Blue tangs generally mate in large resident aggregations over sandy patches between reefs. These fish seem to prefer locations 6 to 10 m deep with reasonably strong currents to sweep the fertilized eggs to sea. Mating readiness is indicated by color changes in the adults, who change from a uniform deep blue to pale blue on the front half of the body and dark blue on the rear half of the body. Courting females and a small number of males break off from the aggregation and release gametes at the water's surface in a behavior called a "spawning rush." Often, spawning rushes are not successful and are broken off by the female. Pair spawning is limited to small populations. (Deloach, 1999; MarineBio.com, 2005; Thresher, 1984)
Prior to a spawning aggregation, small groups of fish travel from nearby reefs before forming schools of over one-hundred individuals. Although spawning aggregations typically occur every day at a given location, they are often restricted to less than 20 individuals. The largest spawning occurs in the late afternoon three to eight days following the full moon in the winter months. However, the exact variables contributing to spawning aggregations are still unknown. It is likely that offshore currents, moon phase, predator abundance, and light levels all play a role in predicting spawning aggregations. Generally, spawning aggregation sites are also used by Acanthurus bahianus and members of the genera Scarus and Sparisoma. Sexual maturity is reached after one year. (Deloach, 1999; MarineBio.com, 2005)
Blue tangs live up to 12 to 15 years in the wild.
Juvenile blue tangs are solitary and occupy home ranges that increase with body size. Juveniles aggressively defend their home ranges from A. bahianus juveniles. Juveniles also avoid damselfishes (Stegastes), that overlap in range with them. Adult blue tangs have three social modes: territorial, wandering, and schooling. Territorial adults chase conspecifics. Schooling adults are not aggressive. Wanderer adults are not aggressive nor do they interact with other individuals like schooling fish do. Wanderers are mostly chased by other fish including conspecifics, ocean surgeons (A. bahianus), and damselfish (Stegastes) (Morgan and Kramer, 2004). Occasionally large, multi-species aggregations are formed, including doctorfish (A. chirurgus) and other surgeonfish (Acanthurus). (Bell and Kramer, 2000; Bester, 2005; Morgan and Kramer, 2004)
Blue tangs are active during the day, hiding in crevices on the reef at night to avoid predators. They are not migratory. Juveniles are rarely seen on reefs, because of their dependence on cover, but intermediate phases and adults are common. (Bester, 2005; Bester, 2005)
Blue tangs use vision to communicate and to locate food. They may also use chemical cues and touch, but little is known about communication and perception channels in these fish.
Blue tangs are herbivorous as adults, feeding largely on filamentous algae. They avoid eating calcareous material, like corals, because they lack the gizzard-like stomach of other surgeonfishes. Acanthurus coeruleus individuals feed singly, in small groups, or in large aggregations numbering over 100. Large aggregations can and in these groups can ravish damselfish gardens on reefs. Blue tangs that live in smaller populations do more foraging in the water column. Blue tangs will also eat plankton. (Bester, 2005; Deloach, 1999)
Predators include reef sharks, tunas, snappers, jacks, groupers, and barracudas. Juveniles may also be taken by trumpetfish. Pelagic eggs are commonly eaten by small bar jacks, yellowtail snappers, and the black durgon.
Because of their flattened shape and sharp caudal spines, it is difficult for predators to swallow blue tangs.
Blue tangs help keep algae populations under control, which prevents the overgrowth and suffocation of corals. Increases in algal density have greatly increased blue tang population size. Most blue tangs move within single reef habitats but they may also live on wider ranges around the reef. (Bester, 2005; MarineBio.com, 2005)
Blue tangs are sometimes used as a bait fish. They are important in the aquarium trade, where they are popular fish. Blue tangs, and other reef fish, attract ecotourism in the form of snorkeling and diving. (Bester, 2005; Froese, et al., 2003)
Blue tangs can cause ciguaterra poisoning if eaten. Their sharp caudal spine can cause painful injuries if people try to handle them. Their sudden movements can cause the spine to create a deep wound, posing a risk of infection. Some species of Acanthurus may have venom associated with the spine as well.
Tanya Dewey (editor), Animal Diversity Web.
Genna Woodruff (author), Hood College, Lori Wollerman (editor, instructor), Hood College.
the body of water between Africa, Europe, the southern ocean (above 60 degrees south latitude), and the western hemisphere. It is the second largest ocean in the world after the Pacific Ocean.
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
uses smells or other chemicals to communicate
the nearshore aquatic habitats near a coast, or shoreline.
humans benefit economically by promoting tourism that focuses on the appreciation of natural areas or animals. Ecotourism implies that there are existing programs that profit from the appreciation of natural areas or animals.
animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature
fertilization takes place outside the female's body
union of egg and spermatozoan
An animal that eats mainly plants or parts of plants.
having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.
Animals with indeterminate growth continue to grow throughout their lives.
offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).
A large change in the shape or structure of an animal that happens as the animal grows. In insects, "incomplete metamorphosis" is when young animals are similar to adults and change gradually into the adult form, and "complete metamorphosis" is when there is a profound change between larval and adult forms. Butterflies have complete metamorphosis, grasshoppers have incomplete metamorphosis.
having the capacity to move from one place to another.
specialized for swimming
the area in which the animal is naturally found, the region in which it is endemic.
reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.
the business of buying and selling animals for people to keep in their homes as pets.
photosynthetic or plant constituent of plankton; mainly unicellular algae. (Compare to zooplankton.)
the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.
condition of hermaphroditic animals (and plants) in which the male organs and their products appear before the female organs and their products
structure produced by the calcium carbonate skeletons of coral polyps (Class Anthozoa). Coral reefs are found in warm, shallow oceans with low nutrient availability. They form the basis for rich communities of other invertebrates, plants, fish, and protists. The polyps live only on the reef surface. Because they depend on symbiotic photosynthetic algae, zooxanthellae, they cannot live where light does not penetrate.
mainly lives in oceans, seas, or other bodies of salt water.
remains in the same area
reproduction that includes combining the genetic contribution of two individuals, a male and a female
associates with others of its species; forms social groups.
uses touch to communicate
defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement
the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.
uses sight to communicate
breeding takes place throughout the year
animal constituent of plankton; mainly small crustaceans and fish larvae. (Compare to phytoplankton.)
Bell, T., D. Kramer. 2000. Territoriality and Habitat Use By Juvenile Blue Tangs, Acanthurus coeruleus . Environmental Biology of Fishes, 58: 401-409.
Bester, K. 2005. "Ichthyology at the Florida Museum of Natural History" (On-line). Accessed September 13, 2005 at http://www.flmnh.ufl.edu/fish/Gallery/Descript/BlueTang/BlueTang.html.
Deloach, N. 1999. Reef Fish Behavior:Florida Caribbean Bahamas. Jacksonville: New Worold Publications.
Froese, R., D. Pauly, D. Woodland. 2003. "Fish Base" (On-line). Accessed September 12, 2005 at http://www.fishbase.org/Summary/SpeciesSummary.php?id=944.
MarineBio.com, 2005. "Acanthurus coeruleus" (On-line). Marine Biology. Accessed September 12, 2005 at http://www.marinebio.com/species.asp?id=277.
Morgan, I., D. Kramer. 2004. The Social Organization of Adult Blue Tangs, Acanthurus coeruleus, on a fringing reef, Barbados, West Indies.. Environmental Biology of Fishes, 71: 261-273.
Thresher, R. 1984. Reproduction in Reef Fishes. Neptune City, NJ: T.F.H. Publications.