Convict tangAcanthurus triostegus

  • Fringing Reef
  • Fauna
  • Convict tang
  • Convict surgeonfish
  • Fiveband surgeonfish
  • Reef fish


Acanthurus triostegus from the family of Acanthuridae is commonly known as the Convict tang, Convict surgeonfish or Five-band surgeonfish. It’s overall body colour can be white or pale grey or grey-green with 4 vertical narrow bands across the body and one that crosses through the eye. It’s scales are small, with tiny projections. Body shape is elongate and oval, with a steep head, small mouth and eyes close to top of the head. Teeth are small with indented tips; there are about 8 to 28 on each jaw. There is a small depressible spine which fits into a groove on the side of the caudal peduncle. The caudal fin is concave.

Habitat and ecology

The Convict Tang is widely present across the Indo-Pacific region and very abundant in parts of its range. It can be found in Yemen but nowhere else in the Arabian Peninsula. This surgeonfish is an inshore species, present in lagoons and seaward reefs with hard substrate. Juveniles are common in tide pools. They are herbivores that feed on algal turfs in large group[1].

In equatorial regions, spawning occurs year round. Elsewhere, spawning is a seasonal event, for example in Hawaii, it coincides with cooler months, February to March. This species forms spawning aggregations. Males display courtship colours. Pair spawning as well as group spawning (10-20) has been observed. Eggs and larvae are pelagic (open ocean); at 3.2cm in length they are called juveniles. Adults can grow up to 27 cm in length[2].


Conservation and management

This species is abundant in parts of its range. Although collected, there are no indications of population declines and it is also found in various MPAs (Marine Protected Areas). This species is in the ‘Least Concern category of the IUCN Red List[3]. No species specific conservation programmes are in place for the Convict Tang.

Fishing for artisanal and recreational purposes is a threat in certain areas. Also, degradation  of coral reefs, their primary habitat, inevitably impacts the population of surgeonfish.


[1] Comeros-Raynal et al., ‘The Likelihood of Extinction of Iconic and Dominant Herbivores and Detritivores of Coral Reefs’.

[2] ‘Convict Surgeonfish, Acanthurus Triostegus (Linnaeus, 1758) - Australian Museum’.

[3] ‘The IUCN Red List of Threatened Species’.

Did you know?

Eagle rays prey upon clouds of eggs and sperms released by the Convict tang during spawning[1].


[1] ‘Acanthurus Triostegus Summary Page’.