Dark Surgeonfish (species: Acanthurus blochii) in Lizard Island Field Guide (Lizard Island Field Guide)
Acanthurus blochii
Dark Surgeonfish

©Lyle Vail: Dark Surgeonfish at Cod Hole near Lizard Island

©Andy Lewis: An individual Dark Surgeonfish feeding

©Andy Lewis: A school of Dark Surgeonfish feeding
Kingdom Animalia
Phylum Chordata
Class Actinopterygii
Order Perciformes
Family Acanthuridae
Genus Acanthurus
Species Acanthurus blochii



Distinguishing features

A medium sized, dark brown fish which appears almost black underwater when viewed from a distance. Fine blue margins on dorsal, anal and tail fins. Pectoral fins uniformly dark, tail spines also dark. The only facial marking is a small orange spot behind the eye which may be indistinct. A white ring is often displayed around the tail base but this is not a distinguishing character.


  • Up to 40 cm (Standard length)

Depth range

  • Depth range data is not yet available.


Similar taxa


©Atlas of Living Australia: Australian distribution

Distribution and habitat preferences

Areas of turf algae and coral rubble on reef flats and slopes. Usually seen in schools.

Found in most reef habitats around the island, although most abundant on exposed reef fronts and nearby flats.


It is a roving herbivore, moving around the reef in schools and feeding on the fine turf algae. The surgeonfish are a very long lived group of fishes - after settlement to the reef, juveniles grow quickly and reach 80% of their maximum size in about 3 years, and then grow very slowly thereafter. Many of them live from 30-50 years. They spawn in groups during the warmer months, when fast running tidal currents coincide with dawn and dusk.

Web resources


  • unspecified - There are a pair of poisonous bony knives at the base of the tail, which can be used to inflict a painful stabbing wound if the fish is handled.


  • Brandl, S.J. and D.R. Bellwood (2013). Morphology, sociality, and ecology: can morphology predict pairing behavior in coral reef fishes? Coral Reefs, 32: 835-836. LIRS catalog number 1718.
  • Brandl, S.J., W.D. Robbins and D.R. Bellwood (2015). Exploring the nature of ecological specialization in a coral reef fish community: morphology, diet and foraging microhabitat use, Proceedings of the Royal Society B, 282: 20151147, doi.org/10.1098/rspb.2015.1147. LIRS catalog number 1908.
  • Ceccarelli, D.M., M.J. Emslie and Z.T. Richards (2016). Post-disturbance stability of fish assemblages measured at coarse taxonomic resolution masks change at finer scales. PLOS One, doi:10.1371/journal.pone.0156232. LIRS catalog number 1971.
  • View all references