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 West Pacific. Occurs mainly on deep coastal reef slopes and outer reef walls, usually in small groups and at moderate depths of about 20m or more. A distinctly coloured species. Adults are easily identified by the mostly blue head and horse-shoe mark above the pectoral fin base. Length to 45cm.