surgeonfishes

Surgeonfishes are a family of marine fishes known for their slender, laterally compressed bodies and distinctive tail fin spines. They include the true surgeonfishes and unicornfishes, collectively referred to as Acanthuridae. A hallmark feature is a pair of sharp, blade-like spines on the caudal peduncle that can be extended as a defensive scalpel. In many species, a horn-like projection on the forehead—especially in the unicornfishes of the genus Naso—gives them their common name.

They are primarily found on shallow tropical and subtropical coral reefs and adjacent habitats across the Indian, Pacific, and Atlantic Oceans. Most species range from about 20 to 60 centimeters in length, with some larger and smaller forms.

Diet is mainly algivorous: they graze on various forms of algae and film on the reef, helping regulate algal growth and reef resilience. Some species take detritus or small invertebrates as supplements.

Surgeonfishes are diurnal and usually occur in small groups or as solitary individuals; several species form spawning aggregations on reefs. Reproduction is typically broadcast spawning, with eggs and sperm released into the water column and planktonic larvae that recruit to reefs.

Human interactions include fisheries harvest and the aquarium trade. Their grazing role makes them important for reef ecology, but populations can be affected by overfishing, habitat degradation, and climate change. Conservation statuses vary among species, with some listed as least concern and others at higher risk.