Humpnose Unicornfish, Naso tonganus (Valenciennes 1835)

Other Names: Bluntnose Unicornfish, Bulbnose Unicornfish, Humphead Unicornfish, Hump-head Unicornfish, Hump-headed Unicorn-fish, Hump-nose Unicorn

A Humpnose Unicornfish, Naso tonganus, off Ribbon Reef #2, Great Barrier Reef, Queensland, September 2015. Source: craigjhowe / License: CC By Attribution-NonCommercial

A silvery- to brownish-grey surgeonfish becoming yellowish-grey below, with a rounded protuberance on the snout, irregular black and pale spots scattered below a prominent hump on the back, a dark dorsal with a pale bluish margin, and a broad blackish submarginal band on the pectoral and caudal fins. Juveniles are densely covered in small dark spots.

Cite this page as:
Bray, D.J. 2020, Naso tonganus in Fishes of Australia, accessed 16 Apr 2024,

Humpnose Unicornfish, Naso tonganus (Valenciennes 1835)

More Info


Shark Bay to North West Cape, including offshore reefs, Western Australia, Ashmore Reef in the Timor Sea, and the far northern Great Barrier Reef, Queensland, and reefs in the Coral Sea, to Jervis Bay, New South Wales; also Cocos (Keeling) Islands and Christmas Island in the eastern Indian Ocean. Elsewhere, the species occurs in the tropical, Indo-west-central Pacific: East Africa to Samoa and throughout Micronesia, northwards to Ryukyu Islands, Japan and southwards to the Great Barrier Reef and New Caledonia.


Dorsal fin V, 28; Anal fin II, 26; Pectoral fin 16; Pelvic fin I, 3; Gill rakers on anterior of first arch 8+9=17; Upper jaw teeth 43.
Body shallow, maximum body depth 36.1; snout with a bulbous tuberosity, rounded in profile, arising from base of upper lip, extending anteriorly well beyond snout tip; nasal groove deep, concave, extending to anterior margin of head; dorsal profile of with prominent narrowly based hump, highest at about base of 5th dorsal-fin spine; jaws protruding; teeth denticulate distally; each side of caudal peduncle with two bony plates with a broad keel-like strong spine; caudal fin slightly emarginate with bluntly angular lobes; scale tubercles with numerous short lanceolate spinules, spinules at posterior of scale slightly elongated.


Browses on algal turf, and filamentous red and green algae.


An important food fish in parts of its range.


In Australia, this species was previously considered a synonym of Naso tuberosus (Johnson 2002).

Similar Species

In the Australian EEZ, the similar Humpnose Unicornfish, Naso tuberosus, is only known from Cocos (Keeling) Islands in the eastern Indian Ocean, and Rottnest Island in south Western Australia.


Named tonganus after Tonga, the type locality.

Species Citation

Naseus tonganus Valenciennes, 1835, Hist. Nat. Poiss. 10: 292. Type locality: Tongatapu, Tonga Islands.


Bray, D.J. 2020


Atlas of Living Australia

Humpnose Unicornfish, Naso tonganus (Valenciennes 1835)


Allen, G.R. 1997. Marine Fishes of Tropical Australia and South-east Asia. Perth : Western Australian Museum 292 pp. 106 pls. (as Naso tuberosus)

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

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. (as Naso tuberosus)

Ceccarelli, D., Choat, J.H., Ayling, A.M., Richards, Z., van Herwerden, L., Ayling, A., Ewels, G., Hobbs, J. –P. & Cuff, B. 2008. Coringa-Herald National Nature Reserve Marine Survey – 2007. Report to the Department of the Environment, Water, Heritage and the Arts by C&R Consulting and James Cook University. 80 pp.

Chiba, S.N. & Matsuura, K. 2012. A Record of Bulbnose Unicornfish, Naso tonganus (Valenciennes, 1835), from the Tokara Group, Southern Japan. Bull. Natl. Mus. Nat. Sci., Ser. A 38(1): 49–52.

Choat, J.H., Abesamis, R., Clements, K.D., McIlwain, J., Myers, R., Nanola, C., Rocha, L.A., Russell, B. & Stockwell, B. 2012. Naso tonganus. The IUCN Red List of Threatened Species 2012: e.T177951A1500716. Downloaded on 17 November 2019.

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.

Coleman, N. 1981. Australian Sea Fishes North of 30°S. Lane Cove, NSW : Doubleday Australia Pty Ltd 297 pp. (as Naso tuberosus)

Crossman, D.J., Choat, J.H. & Clements, K.D. 2005. Nutritional ecology of nominally herbivorous fishes on coral reefs, Marine Ecology Progress Series 296: 129-142.

Ho, H.-C., Shen, K.-N. & Chang, C.-W. 2011. A new species of the unicornfish genus Naso (Teleostei: Acanthuridae) from Taiwan, with comments on its phylogenetic relationship. Raffles Bulletin of Zoolog 59(2): 205-211 See ref online

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

Hutchins, J.B. 1990. Fish survey of South Passage, Shark Bay, Western Australia. pp. 263-278 in Berry, P.F., Bradshaw, S.D. & Wilson, B.R. (eds). Research in Shark Bay: Report of the France-Australe Bicentenary Expedition Committee. Perth : Western Australian Museum. (as Naso tuberosus)

Hutchins, J.B. 1994. A survey of the nearshore reef fish fauna of Western Australia's west and south coasts — The Leeuwin Province. Records of the Western Australian Museum, Supplement 46: 1-66 figs 1-6 (as Naso tuberosus)

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. (as Naso tuberosus)

Hutchins, J.B., Williams, D.McB., Newman, S.J., Cappo, M. & Speare, P. 1995. New records of fishes for the Rowley Shoals and Scott/Seringapatam Reefs, off north-western Australia. Records of the Western Australian Museum 17: 119-123. (as Naso tuberosus)

Johnson, J.W. 2002. Naso mcdadei, a new species of unicornfish (Perciformes: Acanthuridae), with a review of the Naso tuberosus complex. Australian Journal of Zoology 50: 293-311

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.

Klanten,S.O., van Herwerden, L., Choat, J.H. & Blair, D. 2004. Patterns of lineage diversification in the genus Naso (Acanthuridae). Molecular Phylogenetics and Evolution 32(1): 221-235

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. & 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. (as Naso tuberosus)

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. (as Naso tuberosus)

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

Randall, J.E. 2005. Reef and shore fishes of the South Pacific. New Caledonia to Tahiti and the Pitcairn Islands. Honolulu : University of Hawaii Press 707 pp.

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. (as Naso tuberosus)

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. (as Naso tuberosus)

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.

Valenciennes, A. in Cuvier, G.L. & Valenciennes, A. 1835. Histoire Naturelle des Poissons. Paris : Levrault Vol. 10 482 pp. pls 280-306. See ref at BHL

Quick Facts

CAAB Code:37437003

Conservation:IUCN Least Concern

Depth:3-25 m

Habitat:Reef associated

Max Size:60 cm TL

Species Image Gallery

Species Maps

CAAB distribution map