Spotted Unicornfish, Naso brevirostris (Cuvier 1829)

Other Names: Longnose Surgeonfish, Longnosed Unicornfish, Palefin Unicornfish, Short-horned Unicornfish, Short-snouted Unicornfish, Spotted Unicorn

A Spotted Unicornfish, Naso brevirostris, on Flynn Reef, Great Barrier Reef, Queensland, July 2010. Source: Andrew J. Green / Reef Life Survey. License: CC by Attribution

A large brown to greyish unicornfish, often paler anteriorly, with darker vertical lines on the sides, a white truncate to slightly rounded tail with no trailing filaments and a large dark spot at the base, and near-horizontal darker lines on the 'horn'. Subadults have small dark spots on the head and body, and the horn starts as a bump in juveniles from a length of about 10 cm.

Cite this page as:
Bray, D.J. 2019, Naso brevirostris in Fishes of Australia, accessed 16 Apr 2024,

Spotted Unicornfish, Naso brevirostris (Cuvier 1829)

More Info


Ningaloo Reef to the Monte Bello Islands and offshore reefs of Western Australia (juvs south to Rottnest Island), and the northern Great Barrier Reef and reefs in the Coral Sea, to at least Moreton Bay, Queensland (juvs south to Narooma, New South Wales); also Ashmore Reef in the Timor Sea, Christmas Island and Cocos (Keeling) Islands in the eastern Indian Ocean, and the Lord Howe Island region in the Tasman Sea. Elsewhere the species occurs in the tropical, Indo-west-central Pacific (Red Sea and East Africa, east to the Hawaiian, Pitcairn and Line islands).
Small groups inhabit lagoon and seaward reefs, usually in depths to 46 m.


Dorsal fin VI, 27-29; Anal fin II, 27-29; pectoral fin 16-17; Pelvic fin I, 3.Body depth 2.3-2.7 in SL; Adults with a broad-based horn on forehead extending as much as a head length in front of the mouth; horn appears as a bump on forehead in juveniles (in fish 10cm long); each side of caudal peduncle with a pair of bony plates that develop into knife-like keels in adults; posterior caudal-fin margin straight to slightly rounded.


Juveniles and subadults graze on benthic algae, while adults mostly consume gelatinous zooplankton. 


Forms spawning aggregations on the Great Barrier Reef.

Species Citation

Naseus brevirostris Cuvier 1829, Le Règne Animal Vol. 2: 225.  Type locality: Indes.


Bray, D.J. 2019


Atlas of Living Australia

Spotted Unicornfish, Naso brevirostris (Cuvier 1829)


Allen, G.R. & Erdmann, M.V. 2012. Reef fishes of the East Indies. Perth : Tropical Reef Research 3 vols, 1260 pp.

Allen, G.R. & Russell, B.C. 1986. Part VII Fishes. pp. 79-103 in Berry, P.F. (ed.) Faunal Surveys of the Rowley Shoals, Scott Reef and Seringapatam Reef, northwestern Australia. Records of the Western Australian Museum, Supplement 25: 1-106 

Allen, G.R. & Smith-Vaniz, W.F. 1994. Fishes of Cocos (Keeling) Islands. Atoll Research Bulletin 412: 1-21 

Allen, G.R. & Steene, R.C. 1988. Fishes of Christmas Island Indian Ocean. Christmas Island : Christmas Island Natural History Association 197 pp.

Allen, G., Steene, R., Humann, P. & Deloach, N. 2003. Reef fish identification: Tropical Pacific. New World Publications Inc., Jacksonville, FL, USA.

Allen, G.R., Steene, R.C. & Orchard, M. 2007. Fishes of Christmas Island. Christmas Island : Christmas Island Natural History Association 2 edn, 284 pp.

Allen, G.R. & Swainston, R. 1988. The Marine Fishes of North-Western Australia. A field guide for anglers and divers. Perth, WA : Western Australian Museum vi 201 pp., 70 pls.

Bellwood, D.R. & Fulton, C.J. 2008. Sediment-mediated suppression of herbivory on coral reefs: decreasing resilience to rising sea levels and climate change? Limnology and Oceanography 53: 2695-2701.

Binning, S.A. & Fulton, C.J. 2011. Non-lethal measurement of pectoral fin aspect ratio in coral-reef fishes. Journal of Fish Biology 79: 812-818.

Choat, J.H., Abesamis, R., Clements, K.D., McIlwain, J., Myers, R., Nanola, C., Rocha, L.A., Russell, B. & Stockwell, B. 2012. Naso brevirostris. The IUCN Red List of Threatened Species 2012: e.T177990A1513480. Downloaded on 07 May 2019.

Choat, J.H. & Axe, L.M. 1996. Growth and longevity in acanthurid fishes: an analysis of otolith increments. Marine Ecology Progress Series 134: 15-26.

Choat, J.H. & Bellwood, D.R. 1985. Interactions amongst herbivorous fishes on a coral reef: influence of spatial variation. Marine Biology 89: 221-234.

Choat, J.H., Clements, K.D. & Robbins, W.D. 2004. The trophic status of herbivorous fishes on coral reefs 2: Food processing modes and trophodynamics, Marine Biology 145: 445-454.

Choat, J.H. & Robertson, D.R. 2002. Age-based studies on coral reef fishes, pp. 57-80. In: P.F. Sale (ed.) Coral reef fishes: dynamics and diversity in a complex ecosystem. Academic Press, Burlington, San Diego and London.

Comeros-Raynal, M.T., Choat, J.H., Polidoro, B., Clements, K.D., Abesamis, R., Craig, M.T., Lazuardi, M.E., McIlwain, J., Muljadi, A., Myers, R.F., et al. 2012. The likelihood of extinction of iconic and dominant components of coral reefs: the parrotfishes and surgeonfishes. PLoS ONE

Cuvier, G.L. 1829. Le Règne Animal Distribué d'après son Organisation, pour servir de base à l'histoire naturelle des animaux et d'introduction à l'anatomie comparée. Poissons. Paris : Fortin, Masson et Co. Vol. 2 Nouvelle édition, pp. 122-406.

Fisher, R., Leis, J.M., Clark, D.L. & Wilson, S.K. 2005. Critical swimming speeds of late-stage coral reef fish larvae: variation within species, among species and between locations. Marine Biology 147: 1202-1212.

Francis, M. 1993. Checklist of the coastal fishes of Lord Howe, Norfolk, and Kermadec Islands, southwest Pacific Ocean. Pacific Science 47(2): 136-170 figs 1-2

Fulton, C.J. 2005. Wave energy and the role of swimming in reef fish ecology, Ph.D. thesis, James Cook University.

Grant, E.M. 1991. Fishes of Australia. Brisbane : EM Grant Pty Ltd 480 pp.

Heatwole, S.J. & Fulton, C.J. 2012. Behavioural flexibility in reef fishes responding to a rapidly changing wave environment. Marine Biology doi: 10.1007/s00227-012-2123-2.

Hoey, A.S. 2010. The ecosystem role of macroalgal browsing fishes on coral reefs. Ph.D thesis, James Cook University.

Horne, J.B., van Herwerden, L., Choat, J.H. & Robertson, D.R. 2008. High population connectivity across the Indo-Pacific: congruent lack of phylogeographic structure in three reef fish congeners. Molecular Phylogenetics and Evolution 49: 629-638.

Hoschke, A., Whisson, G. & Moore, G.I. 2019. Complete list of fishes from Rottnest Island, pp. 150-161 in Whisson, G. & Hoschke, A. (eds) The Rottnest Island fish book. 2nd ed. Perth : Aqua Research and Monitoring Services, 176 pp.

Hutchins, J.B. 2001. Biodiversity of shallow reef fish assemblages in Western Australia using a rapid censusing technique. Records of the Western Australian Museum 20: 247-270 

Johnson, J.W. 2010. Fishes of the Moreton Bay Marine Park and adjacent continental shelf waters, Queensland, Australia. pp. 299-353 in Davie, P.J.F. & Phillips, J.A. Proceedings of the Thirteenth International Marine Biological Workshop, The Marine Fauna and Flora of Moreton Bay. Memoirs of the Queensland Museum 54(3) 

Klanten, S.O. 2003. Molecular phylogeny, temporal patterns of lineage diversification and phylogeography of the surgeonfish genus Naso (Acanthuridae), Ph.D. thesis, James Cook University.

Kuiter, R.H. 1992. Tropical Reef-Fishes of the Western Pacific, Indonesia and Adjacent Waters. Jakarta : PT Gramedia Pustaka Utama 314 pp. pls. 

Kuiter, R.H. 1993. Coastal Fishes of South-eastern Australia. Bathurst : Crawford House Press 437 pp. 

Kuiter, R.H. 1996. Guide to Sea Fishes of Australia. A comprehensive reference for divers and fishermen. Sydney, NSW, Australia : New Holland Publishers xvii, 434 pp. 

Kuiter, R.H. & Debelius, H. 2001. Surgeonfishes, Rabbitfishes and Their Relatives. A comprehensive guide to Acanthuroidei. Chorleywood, U.K. : TMC Publishing 208 pp. 

Oxley, W.G., Ayling, A.M., Cheal, A.J. & Thompson, A.A. 2003. Marine surveys undertaken in the Coringa-Herald National Nature Reserve, March-April 2003. Townsville : Australian Institute of Marine Science 59 pp. 

Oxley, W.G., Emslie, M., Muir, P. & Thompson, A.A. 2004. Marine surveys undertaken in the Lihou Reef National Nature Reserve, March 2004. Townsville : Australian Institute of Marine Science i-vii, 1-67 pp.

Randall, J.E. 2001. Surgeonfishes of Hawai'i and the World. Honolulu : Mutual Publishing and Bishop Museum Press 125 pp. 

Randall, J.E. 2001. Zanclidae, Acanthuridae. pp. 3651-3683 in Carpenter, K.E. & Niem, T.H. (eds). The Living Marine Resources of the Western Central Pacific. FAO Species Identification Guide for Fisheries Purposes. Rome : FAO Vol. 6 pp. 3381-4218. 

Randall, J.E., Allen, G.R. & Steene, R. 1990. Fishes of the Great Barrier Reef and Coral Sea. Bathurst : Crawford House Press 507 pp. figs. 

Randall, J.E., Allen, G.R. & Steene, R. 1997. Fishes of the Great Barrier Reef and Coral Sea. Bathurst : Crawford House Press 557 pp. figs. 

Russell, B.C., Larson, H.K., Hutchins, J.B. & Allen, G.R. 2005. Reef fishes of the Sahul Shelf. The Beagle, Records of the Museums and Art Galleries of the Northern Territory Supplement 1 2005: 83-105

Tettamanti, T., de Busserolles, F., Lecchini, D., Marshall, N.J. & Cortesi, F. 2020. Visual system development of the spotted unicornfish, Naso brevirostris (Acanthuridae). Journal of Experimental Biology 222:  jeb209916

Quick Facts

CAAB Code:37437026

Conservation:IUCN Least Concern

Depth:2-122 m (usually to 46 m)

Habitat:Reef associated

Max Size:60 cm TL

Species Image Gallery

Species Maps

CAAB distribution map