The common name "surgeonfish" is derived from a characteristic that clearly distinguishes Acanthuridae from other fish families: the spines or "scalpels" on the caudal peduncle, one or more on each side. Based primarily on differences in this characteristic, the family can be divided into three subfamilies: The Acanthurinae, in which the peduncular spine rests in a groove and can be erected in defence during the fights, the Nasinae and Prionurinae in which the peduncular feature is arranged as one or more fixed blades on each side, that are sharp and elongate with age.
Place of origin:Indian Ocean
Widespread Indo-West Pacific. Usually occurs in algae rocky habitats. Coastal reefs and harbours to outer reef gutters and channels to about 20m depth. Adults usually in small groups, but form large schools in some oceanic locations. Juveniles are often seen feeding with mixed species aggregations. Adults identified by the small orange spots on their head, blue to mauve tail and a dark spot at the end of the anal and dorsal fin-base. Juveniles brown to bluish black when small, and the head with orange scribbles that break up into spots with growth. Length to 20cm.