Latin name

Acanthurus triostegus

Other name

Convict surgeon, convict tang or fiveband surgeonfish.

Identification

The Convict surgeonfish has a large, laterally compressed, moderately oval body. The mouth is non-retractable, small and set low on the head. The teeth are fixed, strong, close together, shovel shaped with serrated edges. There is a sharp, lanceolate spine on the tail, which is hidden in a fossa but can be raised. The scales are small. Serrated teeth on sides and top. The gill stamens are 18-22 in the anterior row, 19-24 in the posterior row.

Features of fish fins

The dorsal fin is continuous, without a notch, with 9 spiny and 22-26 soft rays. The anal fin has 3 spiny and 19-22 soft rays. Pectoral fin with 2 spiny and 13 soft rays. The caudal fin is halfmoon shaped. This species has fewer soft rays than other members of the genus.

Fish colouring

The body is olive grey with a white abdomen, often with a clear demarcation line. The Convict surgeonfish differs from other species in the genus by its inherent colouration. It has 5 narrow black vertical stripes, the first of which runs through the eye. There is a dark spot on the caudal trunk from above and below.

Distribution

They are widespread in the Indo-Pacific region. Japan, Hawaii, Taiwan (China), Philippines, Melanesia, Polynesia, Australia, South Africa.

Habitat

Marine, tropical, benthopelagic, coastal, reef associated fish. They usually live at depths between 0 and 90 metres.

Size

The maximum body length of these fish is 27 cm, but is usually down to 17 cm.

Behavior

Adults live in lagoons and coastal reefs with solid substrate. Juveniles are abundant in tidal pools. They sometimes form schools.

Food and feeding habits

They are mainly herbivorous fish, but sometimes they also feed on small benthic invertebrates. They often feed near freshwater drains, where some algae grow on rocks.

Reproduction

They form spawning groups. The size of the metamorphosis from larva to juvenile is 3.2 cm.

Fishing

This species is commercially important for fishing.

Relationship with a person

It is used as a food fish. There have been reports of ciguatera poisoning.