Sleek Unicornfish, Naso hexacanthus (Bleeker 1855)

Other Names: Blue-tail Unicorn, Sleek Unicorn, Thorpe's Unicornfish

Sleek Unicornfish, Naso hexacanthus, on Day Reef near Lizard Island, Great Barrier Reef, Queensland. Source: Anne Hoggett, Lizard Island Field Guide / License: CC by Attribution

A brownish to bluish-grey surgeonfish becoming yellowish below, with a black margin on the cheek and gill cover. This species is easily confused with Naso caesius.

Video of a Sleek Unicornfish changing colour.

Cite this page as:
Bray, D.J. 2022, Naso hexacanthus in Fishes of Australia, accessed 19 Apr 2024,

Sleek Unicornfish, Naso hexacanthus (Bleeker 1855)

More Info


Offshore reefs of Western Australia, Ashmore Reef in the Timor Sea, and the northern Great Barrier Reef to Moreton Bay, Queensland, also reefs in the Coral Sea; also Cocos (Keeling) Islands and Christmas Island in the eastern Indian Ocean, and the Lord Howe Province in the Tasman Sea. Elsewhere the species is widespread in the Red Sea and tropical, Indo-west Pacific.
Inhabits seaward reefs, and large schools are usually seen feeding in the water column near drop-offs.


Feeds in midwater on zooplankton.


The species is easily confused with Naso caesius and some records of Naso hexacanthus may be misidentifications of N. caesius.

Similar Species

The similar Silverblotched Unicornfish, Naso caesius, differs in having smaller bladelike caudal spines that do not become sharply pointed and antrorse in large males, a pale tongue (vs. black in N. hexacanthus), overall bluish grey (vs. yellowish ventrally in N. hexacanthus), in lacking dark borders on the opercle and preopercle (present in N. hexacanthus).


The specific name hexacanthus is from the Latin hexa (= six) and akanthus (= horn, point, thorn), in reference to the six dorsal-fin spines of this species.

Species Citation

Priodon hexacanthus Bleeker, 1855, Natuurwetensch. Tijdschr. Nederland. Indiƫ 8: 393, 421. Type locality: Ambon (as Amboina), Indonesia.


Bray, D.J. 2022


Sleek Unicornfish, Naso hexacanthus (Bleeker 1855)


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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.

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Bleeker, P. 1855. Zesde bijdrage tot de kennis der ichthyologische fauna van Amboina. Natuurwetenschappelijk Tijdschrift voor Nederlandsch Indiƫ 8: 391-434. See ref at BHL

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.

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Choat, J.H., McIlwain, J., Abesamis, R., Clements, K.D., Myers, R., Nanola, C., Rocha, L.A., Russell, B. & Stockwell, B. 2012. Naso hexacanthus. The IUCN Red List of Threatened Species. Version 2015.2. . Downloaded on 02 August 2015.

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.

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Francis, M. 2019. Checklist of the coastal fishes of Lord Howe, Norfolk and Kermadec Islands, southwest Pacific Ocean Version: 2019.1

Herre, A.W. 1927. Philippine surgeon fishes and moorish idols. Philippine Journal of Science 34(4): 403-478.

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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.

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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

Quick Facts

CAAB Code:37437028

Conservation:IUCN Least Concern

Depth:15-135 m

Habitat:Reef associated

Max Size:75 cm TL

Species Image Gallery

Species Maps

CAAB distribution map