Whitemargin Unicornfish

Naso annulatus is a tropical fish found throughout the Indo-Pacific. It can reach a length of 100 cm, making it one of the largest members of the family Acanthuridae.

Description

It is plain brown or olivaceous in color, paler below and has a large, distinguishing "nasal" protrusion. The tail is black surrounded by a white margin. It has two scutes on the left side. These are found on the caudal peduncle near the tail. Juveniles often have a white ring around the caudal peduncle.

Distribution

Indo-Pacific: East Africa, including the Mascarene Islands to the Hawaiian, Marquesan, and Tuamoto islands, north to southern Japan, south to Lord Howe Island.

Habitat

It is often found in large schools off tropical reefs, and it feeds on large zooplankton during the day and shelter within the reef during the night. Juveniles can be found on reefs around shallow lagoons at depths as little as 1 m. Adults are usually seen in small schools at depths over 20 m on reef dropoffs.