Whitecheek Tang

The Whitecheek Tang (Acanthurus nigricans) is a dark-bodied surgeonfish easily distinguished by the bright white patch on its cheek, just below and behind the eye, which stands out sharply against its otherwise dark brown to blackish coloration. A narrow orange band traces the margin of the tail, adding a splash of color to an otherwise somber fish. It is widespread across the Indo-Pacific and into the eastern Pacific, typically found grazing algae from reef rubble and rock in relatively shallow water. The species is also sometimes called the gold-rim tang, referencing the fine orange edging visible along parts of the fins and tail in good light.

• Cheek patch: Bright white crescent-shaped mark below and behind the eye, the species' most diagnostic feature.
• Body color: Dark brown to blackish overall.
• Tail: Narrow, bright orange band along the trailing edge of the caudal fin.
• Tail spine: Pale scalpel-like spine at the base of the tail.
• Look-alikes: Similar in overall shape to other dark Acanthurus species, but the combination of white cheek patch and orange tail edge is unique to this species.

Whitecheek Tangs have one of the broadest ranges of any surgeonfish, occurring across the Indo-Pacific from East Africa to the central Pacific and extending into the eastern Pacific around offshore islands. They inhabit coral reef flats, lagoons, and outer reef slopes, typically in shallow water from the surface down to about 27 meters. They favor areas with a mix of coral, rock, and rubble that support dense algal turf growth, often congregating in surge-influenced zones near the reef crest. The species tolerates a wide range of reef conditions across its extensive geographic distribution.

Whitecheek Tangs graze filamentous algae from rock, rubble, and dead coral surfaces throughout the day, often foraging alone or in small loose groups alongside other herbivorous reef fish. They can be territorial over productive grazing patches but are generally less overtly aggressive than some other surgeonfish species. Like all members of the family, they possess a sharp scalpel-like spine at the base of the tail used defensively against predators and competitors. Reproduction follows the typical surgeonfish pattern of pelagic spawning, with adults gathering to release eggs and sperm into open water, often around dusk, producing planktonic larvae that drift before eventually settling onto reef habitat as juveniles.