Acanthurus chirurgus
    Ecological Descriptors
Habitat Size (cm) Diet Behaviour Sex 
Co, R, 35 Veg Sh F
Adults: Body laterally compressed, oval in shape, with relatively long dorsal and anal fins and a crescent tail.  Body bluish gray to dark brown, and pale or darken dramatically (
Dark Phase). Body with 10 to 12 body bars, (Ocean Surgeonfish, A. bahianus never has bars) although they may be faint. Several markings radiate from the eye. Dorsal, anal and tail fins often with blue or white borders. Base of tail with a dark sharp spine (like a surgeon's scalpel), sometimes with a white/ blue highlight behind the spine. Sometimes pale band on caudal peduncle. Pectoral fins often with dark leading edge.

Inhabits shallow reefs or rocky areas, down to 25 m. Often in loose aggregations. Mainly diurnal.It grazes on many species of benthic algae, occasionally on seagrass. It also feeds on the film of algae on the surface of sand undisturbed by surge The sharp spines at both sides of the base tail are used as defensive weapons by slashing their tails from side to side. When not in use, they are folded backwards against the body.  In most locations fish settle inshore, grow to near full size and then, when 2 to 6 years old, relocate permanently to outer reefs.

Life Cycle:
Terminal size is reached at around age 4, and most of the growth occurred within the first 10% of the lifespan, and approximately 85% of full size is attained within the first year. The mean maximum age fluctuated from 7 years in Belize to 16 years in Bermuda with a maximum longevity of 30 years in Bermuda.
Doctorfish Juvenile
(C) Robertson & Van Tassell
(C) Ross Robertson
Doctorfish Dark Phase