Lined Surgeonfish

The Lined Surgeonfish, also known as the Striped or Clown Surgeonfish, is one of the most vividly patterned members of the family Acanthuridae. It ranges across the Indo-Pacific from the Red Sea and East Africa to French Polynesia, typically inhabiting shallow, wave-exposed reef crests. The species is well known among reef researchers for its strongly territorial behavior, as individuals aggressively defend algal turf patches, or 'farms,' against intruding herbivores. Its bold blue, black, and yellow horizontal stripes make it one of the easiest surgeonfishes to identify underwater. The species is common and not currently threatened, though its narrow habitat preference for high-energy reef crests makes it sensitive to reef degradation in shallow zones.

Distinctive markings make this species easy to recognize:

• Elongate oval body with alternating blue-black and yellow-orange horizontal stripes running from head to tail
• Bright blue lips
• Yellow pectoral fins contrasting with the striped body
• Deep blue, spine-bearing caudal peduncle
• Crescent-shaped tail fin

Adults reach about 38 cm. Its stripe pattern is unique among Indo-Pacific surgeonfishes, distinguishing it from the plainer Brown or Ringtail Surgeonfish. Juveniles show similar but slightly duller striping. It is often seen alone or in small groups defending patches of algal turf rather than in large open schools like many relatives.

Lined Surgeonfish are specialists of shallow, high-energy reef crests and reef flats exposed to strong surge and wave action, typically in less than 3 m of water. Their range extends across the Indo-Pacific from the Red Sea and East Africa to Micronesia and French Polynesia, and south to the Great Barrier Reef. They favor areas with abundant algal turf growing on reef pavement, which individuals cultivate and defend as feeding territories. This preference for turbulent, shallow zones sets them apart from many reef fish that avoid such exposed habitat, and it limits their depth range compared to deeper-dwelling surgeonfish relatives.

This species is notably territorial, with individuals establishing and vigorously defending patches of algal turf against nearly all intruders, including much larger fish and other surgeonfish species. Defense involves rapid charges and slashing strikes with the sharp caudal spine. Despite this aggression toward competitors for its algae farm, it may tolerate schooling surgeonfish that briefly overwhelm its defenses in large numbers to feed. It is a diurnal grazer, active through daylight hours in the shallow surge zone it inhabits. Spawning follows the broadcast pattern typical of the family, with pelagic eggs and larvae dispersing offshore before returning to settle on shallow reef crests as juveniles.