Order : Uncertain
Family : ACANTHURIDAE
Species : Acanthurus spp.

There are around 40 species of surgeonfish in the genus Acanthurus.

The Convict Surgeonfish, Acanthurus triostegus, featured here, is a typical example. It is a tropical reef dweller which inhabits quiet lagoons and rougher, wave-dominated seaward reefs. According to Fishbase, typical examples reach up to 17 cm in in length, but exceptionally large examples may reach 27 cm.

Its vernacular name derives from the striped uniforms worn by convicts in some countries. Its overall body colour and fins are yellowish-grey to white. There are 4 narrow, vertical stripes on each flank and a fifth stripe on each side of the head, passing through the eye.

There is also a short stripe on the caudal peduncle i.e. at the base of the tail fin. On either side of the caudal peduncle is a sharp, collapsible, forward-pointing spine or 'scalpel' (hence these fishes are called 'surgeonfishes'):  this is a defining feature of members of the Acanthuridae family.

This species grazes on marine algae adhering to rocky reefs and hard substrates: its teeth are adapted to this diet.

The Convict Surgeonfish is widespread, occurring throughout much of the Indian Ocean, Southeast Asia and the Pacific Ocean.

Figs 1 and 2 : Acanthurus triostegus from French Polynesia, in the central Pacific Ocean.

Fig 3 : Calm, tidal pool behind at low tide: the Convict Surgeonfish grazes on filamentous algae in such habitats.


References : F3

Fishbase