Naso lituratus


Taxonomy [top]

Kingdom Phylum Class Order Family

Scientific Name: Naso lituratus
Species Authority: (Forster, 1801)
Common Name/s:
English Orange Spine Surgeonfish, Poll Unicornfish, Masked Unicornfish, Naso trang, Barcheek Unicornfish, Orange-spine Unicornfish, Pacific orange-spine Unicorn, Clown Tang, Redlip Surgeonfish, Smooth-head Unicornfish, Striped-faced Unicornfish, Striped Unicornfish
French Nason à Eperons Oranges
Spanish Barbero de Aguijón Naranja
Acanthurus lituratus Forster, 1801
Aspisurus carolinarum Quoy & Gaimard, 1825
Callicanthus lituratus (Forster, 1801)
Monoceros garretti Seale, 1901
Naso literatus (Forster, 1801)
Prionurus eoume Lesson, 1831
Taxonomic Notes: Naso lituratus was observed to be actively hybriding with N. elegans at Cocos-Keeling (J.H. Choat pers. comm. 2010, Klanten 2003).

Assessment Information [top]

Red List Category & Criteria: Least Concern ver 3.1
Year Published: 2012
Date Assessed: 2010-05-06
Assessor/s: McIlwain, J., Choat, J.H., Abesamis, R., Clements, K.D., Myers, R., Nanola, C., Rocha, L.A., Russell, B. & Stockwell, B.
Reviewer/s: Edgar, G. & Kulbicki, M.
Naso lituratus is widespread throughout most of the Pacific. It is common and locally abundant in parts of its range. Although heavily targeted for the aquarium trade in parts of its range (Hawaii), it is found in well-policed marine reserves and Fish Replenishment Areas. Harvest is not considered a global threat although there may be some localized declines in areas where it is harvested. There are no significant population reductions at the present time. It is therefore listed as Least Concern. However, we recommend monitoring of the harvest levels of this species

Geographic Range [top]

Range Description: Naso lituratus is widespread from Cocos-Keeling in the eastern Indian Ocean to French Polynesia and the Pitcairn group, northwards to Honshu, Japan, southwards to Ningaloo reef, southern Great Barrier Reef, Australia, New Caledonia and Rapa. It is reported in the eastern Pacific from Clipperton Island as a vagrant. Records from the Indian Ocean west of Cocos-Keeling refer to N. elegans.

American Samoa (American Samoa); Australia; Cambodia; China; Christmas Island; Cocos (Keeling) Islands; Cook Islands; Disputed Territory (Paracel Is., Spratly Is.); Fiji; France (Clipperton I.); French Polynesia; Guam; Indonesia; Japan; Kiribati (Gilbert Is., Kiribati Line Is., Phoenix Is.); Malaysia; Marshall Islands; Micronesia, Federated States of ; Nauru; New Caledonia; Niue; Northern Mariana Islands; Palau; Papua New Guinea; Philippines; Pitcairn; Samoa; Singapore; Solomon Islands; Taiwan, Province of China; Thailand; Timor-Leste; Tokelau; Tonga; Tuvalu; United States (Hawaiian Is.); United States Minor Outlying Islands (Howland-Baker Is., Johnston I., Midway Is., US Line Is., Wake Is.); Vanuatu; Viet Nam; Wallis and Futuna
FAO Marine Fishing Areas:
Indian Ocean – eastern; Pacific – eastern central; Pacific – northwest; Pacific – southwest; Pacific – western central
Range Map: Click here to open the map viewer and explore range.

Population [top]


Naso lituratus is among the top 10 commercial aquarium species collected in Hawaii with reported catches of 298,884 individuals from FY 1976-2003 (Walsh et al. 2004). Overall aquarium catch in fiscal years 2004 through 2006 reported 13,149 individuals caught/year and a value of $52,997/ year (Friedlander 2006). It is the fourth most collected aquarium fish in West Hawaii. There was a non-significant decrease in overall density across Fish Replenishment Areas (FRAs) surveyed from 1999-2009. However, the FRAs were shown to be effective in terms of increases inside the FRAs relative to long term marine protected areas. There was minimal recruitment into West Hawaii in the last decade = 0.05/100 m2For FY 2005-2009, the total number of individuals caught was 29,859 with a total value of $122,090 (Walsh et al. 2010).

It was recorded as more abundant in shallow stations where there was high cover of living hard corals at the Nha Trang Bay MPA (Nguyen and Phan 2008). It was recorded as common in terms of relative abundance in Milne Bay Province, northern Bismarck Sea, Papua New Guinea and Raja Ampat, Indonesia (Allen 2003, 2009, 2003b).  It is moderately common in the Philippines (Werner and Allen 2000, Palawan Council for Sustainable Development unpub. data, R. Abesamis and C. Nanola pers. comm. 2010); the densities seem to be low in the central Visayas (R. Abesamis and C. Nanola pers. comm. 2010).

In the commercial coral reef fishery in Pohnpei, acanthurids contribute nearly 30% of the total catch volume and include the most heavily targeted species, N. lituratus and N. unicornis (Rhodes et al. 2008). It was the fourth most dominant species in Tutuila, Aunuu, and Taema Banks, American Samoa contributing to 2.7% of total fish biomass and 1.7% of numerical abundance (Sabater and Tofaeono 2006). In Moorea Is., French Polynesia, a total of 292, 994 individuals was recorded in fish visual surveys conducted from 1990-1993 (Lecchini et al. 2006). It is very abundant on the outer slope of Tiahura (Moussa 2009). It is abundant in the American Samoa National Park (National Park of Samoa Checklist of Fishes accessed 21 April 2010).

On Saipan, N.lituratus accounted for 4.5% of the total fish landings and 16.5% of the acanthurids landings (P. Houk unpub. data). The numerical abundance of N. lituratus in the shallow reefs around Saipan from underwater visual census data was 7% of all acanthurids  with an average density of 4 ind./450 m2 (J. McIlwain unpublished data).  On Guam the average density was 9/450 m2 where it accounts for 22% of the total acanthurid fishery (J. McIlwain and Division of Aquatic and Wildlife Resources unpub. data). A mark-release-resight study on Guam revealed population size of 40,000 individuals in a single bay (Piti Marine Preserve) covering an area of 10,578 m(A. Marshell unpub. thesis).

Densities of 30.1 gm2 were recorded at outer reef slopes at Yyin on the west coast of Yap. Overall biomass for both sites on Yap (Riiken and Yyin) was 5.9 gm2 and 5.6 gm2. At one site on Chuuk (Romanum) the biomass across all sites was 2.5 gm2.  At the same location (Chuuk) Naso lituratus contributes up to 32% of the total catch in the lagoon, outer reef and passage (SPC unpub. report 2006).  

In the central Philippines, density and biomass of herbivorous fish in reserves had positive relationships with duration of reserve protection. There was an order of magnitude difference in mean biomass between fished sites and marine protected areas (0.5-11 years of protection) (Stockwell et al. 2009).

Population Trend: Stable

Habitat and Ecology [top]

Habitat and Ecology: Orange Spine Surgeonfish (Naso lituratus) is usually encountered in less than 30 m, but reported as deep as 90 m in coral reefs and rocky bottoms. It is sometimes seen in large aggregations but is usually solitary (Randall 2001a,b). It feeds on macroalgae (Choat et al. 2004).  It is classified as a browser (Choat and Clements 1998). It has high levels of SCFAs (short chain fatty acids) and is known to harbour abundant microbiota in the posterior intestine (Clements and Choat 1995). Maximum age recorded from the Great Barrier Reef was 39 years (Choat and Robertson 2002a), Cocos-Keeling 15 years. This species has a similar maximum size at both of these sites, 37 cm, (FL) and is significantly smaller than N. elegans (J.H. Choat pers. comm. 2010). The maximum size in Guam is 27 cm (FL) (A. Marshell unpub. thesis). N. lituratus has a highly disparate size distribution (J.H. Choat pers. comm. 2010). 


The sexes are separate among the acanthurids (Reeson 1983). Sexual dimorphism is evident from the length of the caudal filament which is present in males but not females (J.H. Choat pers. comm. 2010). This was confirmed with histology of gonads (A. Marshell unpub. thesis). This species was reported to form spawning aggregations on the Great Barrier Reef (Squire and Samoilys unpub.).

Histology of a number of 12-14 cm individuals collected from Guam found all had mature stage oocytes, although it's unlikely that fish of this size are making a contribution to the overall reproductive output. Spawning occurs year round in Guam, females with matures oocytes and mature males occured in most months of 2008-2009. Newly settled N. lituratus preferred high coral cover over coral rubble (J. McIlwain unpub. data).
Systems: Marine

Threats [top]

Major Threat(s): There were differences of an order of magnitude in mean biomass between fished and protected areas in the Philippines (Stockwell et al. 2009). Naso lituratus is heavily targeted in areas where fishery management is close to non-existent and coral reef areas are impacted by anthropogenic threats.

Surgeonfishes show varying degrees of habitat preference and utilization of coral reef habitats, with some species spending the majority of their life stages on coral reef while others primarily utilize seagrass beds, mangroves, algal beds, and /or rocky reefs. The majority of surgeonfishes are exclusively found on coral reef habitat, and of these, approximately 80% are experiencing a greater than 30% loss of coral reef area and degradation of coral reef habitat quality across their distributions. However, more research is needed to understand the long-term effects of coral reef habitat loss and degradation on these species populations. Widespread coral reef loss and declining habitat conditions are particularly worrying for species that recruit into areas with live coral cover especially as studies have shown that protection of pristine habitats facilitate the persistence of adult populations in species that have spatially separated adult and juvenile habitats (Comeros-Raynal et al. 2012).

Conservation Actions [top]

Conservation Actions: There are no species-specific conservation measures in place. However, its distribution overlaps with several marine reserves in parts of its range.  In Hawaii, nine Fish Replenishment Areas were established in 2000. These areas prohibit marine aquarium organism collecting within approximately 30% of the Kona coast nearshore habitat (Kusumaatmadja et al. 2004). In 2002, the Marine Aquarium Council initiated a three-year project designed to enhance coral reef conservation in the islands by facilitating MAC certification of qualifying aquarium industry operators and encouraging market incentives (MAC 2003). Despite the creation of FRAs on the Big Island of Hawaii, densities of N. lituratus sub-adults and juveniles has continued to decline since a peak in 2005. This is attributed to the high inter-annual variability in recruitment. In the deeper areas where transects are conducted, there has been no recorded replenishment of young-of-the-year. Consequently, densities of younger fish have declined because of ontogenetic movement into adult habitat and natural mortality (Walsh et al. 2010).

For reef slopes on Guam (4-12 m) there was no evidence of a biomass buildup within Marine Reserves when compared with adjacent fished sites (J. McIlwain unpub. data).
Citation: McIlwain, J., Choat, J.H., Abesamis, R., Clements, K.D., Myers, R., Nanola, C., Rocha, L.A., Russell, B. & Stockwell, B. 2012. Naso lituratus. In: IUCN 2013. IUCN Red List of Threatened Species. Version 2013.2. <>. Downloaded on 19 April 2014.
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