Adult male bluespine unicornfish tend to have the most developed rostral horn, but both males and females do show this characteristic trait. The function of this horn is unknown.
  • Size

    Up to 27.6 inches (70 cm)
  • Diet

    Coarse and leafy brown algae
  • Range

  • Habitat

    Channels, moats, lagoons and seaward reefs

Physical Characteristics

  • The body is usually greenish-gray in color with a bony horn or rostrum protruding from the front of its head in between the eyes.
  • Dorsal and anal fins are yellowish with thin blue lines.
  • Two blue plates with sharp, forward-pointing spines on either side of the caudal peduncle.
  • Thick leathery skin with tiny non-overlapping scales and small teeth with finely serrated edges.
  • Lobes of the caudal fin are extended into slender thread-like filaments; more apparent in the male.
  • Can reach approximately 27.6 inches (70 cm) in length.

Animal Fact

This unicornfish develops long, trailing tail filaments as it grows.

Diet / Feeding

  • Diet consists of coarse and leafy brown algae.

Range / Habitat

  • Occurs in the Indo-Pacific from the Red Sea and East Africa across the tropical Pacific to southern Japan, throughout Micronesia and Hawaii.
  • Juveniles live on clear coastal reefs with algae growth.
  • Adults prefer shallow reef slopes adjacent to deep water.
  • Found in channels, moats, lagoons and seaward reefs, particularly in areas with strong surges, preferring depths usually no greater than about 33 feet (10 m).

Reproduction & Growth

  • Has been observed practicing pair spawning, particularly at the outermost area of a foraging group.
  • In some areas, they have been observed migrating in schools around the outer reef edges and spawning during both the full and new moons.

Conservation Status

  • “Least Concern” on the IUCN Red List.

Additional Information

  • With age, the male tends to have a better-developed horn, peduncular spines (spines in plates just before the tail), and caudal (tail) filaments than its female counterpart.
  • Usually swims within a small group.
  • The function of the rostral horn on the forehead is unknown.


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