''Acanthurus olivaceus'', also known as the orange-band surgeonfish, the orange-shoulder surgeonfish or the orangebar tang, is a member of the

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

Acanthuridae Acanthuridae are the family of surgeonfishes, tangs, and unicornfishes. The family includes about 86 extant species of marine fish living in tropical seas, usually around coral reefs. Many of the species are brightly colored and popular in aq ...

, the surgeonfishes. It lives in the tropical waters of the Indo-west Pacific.

Description

The orange band surgeonfish is a deep-bodied, laterally-compressed oval fish, rather over twice as long as it is deep, with a maximum length of , although a more typical length is . Both dorsal and anal fins are long and low, extending as far as the caudal peduncle. The dorsal fin has nine spines and 23 to 25 soft rays while the anal fin has three spines and 22 to 24 soft rays. The tail fin is crescent-shaped, the points growing longer as the fish gets older. The adult fish is greyish-brown; a sharp vertical line usually separates the paler front half of the fish from the darker hind portion. There is a distinctive orange bar, surrounded by a purplish-black margin, immediately behind the top of the gill cover, and blue and orange lines at the bases of the fins. Like all surgeonfish, this species has a pair of scalpel-like scales that project upward from the caudal peduncle. Larger males develop a convex snout which clearly differentiates them from females. Juvenile fish are yellow.

Distribution and habitat

This fish is found in the tropical eastern Indian Ocean and the western Pacific Ocean. Its range extends from

Christmas Island Christmas Island, officially the Territory of Christmas Island, is an Australian external territory comprising the island of the same name. It is located in the Indian Ocean, around south of Java and Sumatra and around north-west of the ...

and the

Cocos Keeling Islands ) , anthem = "''Advance Australia Fair''" , song_type = , song = , image_map = Australia on the globe (Cocos (Keeling) Islands special) (Southeast Asia centered).svg , map_alt = Location of the Cocos (Keeling) Islands , map_caption = ...

to southern Japan, Western, Northern and Eastern Australia, Indonesia, the Philippines and Hawaii. It is associated with reefs, often on outer slopes and in more exposed locations. As an adult, it is a solitary fish or sometimes joins schools, with a depth range of between about , but juveniles are found in shallower water in sheltered locations in small groups.

Ecology

The orange band surgeonfish feeds on

detritus In biology, detritus () is dead particulate organic material, as distinguished from dissolved organic material. Detritus typically includes the bodies or fragments of bodies of dead organisms, and fecal material. Detritus typically hosts commun ...

and on algae growing on the seabed, as well as the film of

diatom A diatom (Neo-Latin ''diatoma''), "a cutting through, a severance", from el, διάτομος, diátomos, "cut in half, divided equally" from el, διατέμνω, diatémno, "to cut in twain". is any member of a large group comprising sev ...

s and filamentous algae that grows on sand and other substrates. It often forms schools with parrotfish, tangs and other species of surgeonfish, which all have similar diets; their grazing is important in maintaining

biodiversity Biodiversity or biological diversity is the variety and variability of life on Earth. Biodiversity is a measure of variation at the genetic (''genetic variability''), species (''species diversity''), and ecosystem (''ecosystem diversity'') l ...

by keeping rocks free from excessive growth of algae so that coral larvae can find suitable habitat to settle. The fish can change colour from dark to pale almost instantaneously.

Status

The orange band surgeonfish has a wide distribution in the tropical Indo-Pacific region and is moderately common. It is sometimes found in fish markets and in the aquarium trade but is not a species targeted by fisheries. No particular threats have been recognised, so the

International Union for Conservation of Nature The International Union for Conservation of Nature (IUCN; officially International Union for Conservation of Nature and Natural Resources) is an international organization working in the field of nature conservation and sustainable use of natu ...

has listed its conservation status as being of

least concern A least-concern species is a species that has been categorized by the International Union for Conservation of Nature (IUCN) as evaluated as not being a focus of species conservation because the specific species is still plentiful in the wild. T ...

References

External links

Orangespot Tang care sheet at FishGeeks

Encyclopedia of Life: ''Acanthurus olivaceus'' (Orange Shoulder Tang)
* {{Taxonbar, from=Q1481899 Acanthurus Fish of Hawaii Fish described in 1801