|Scientific Name:||Acanthurus nigricans|
|Species Authority:||(Linnaeus, 1758)|
Acanthurus aliala Lesson, 1831
Acanthurus glaucoparecius Cuvier, 1829
Acanthurus glaucopareius Cuvier, 1829
Chaetodon nigricans Linnaeus, 1758
|Taxonomic Notes:||Acanthurus nigricans is a member of the A. achilles species complex known for their propensity to hybridize (Randall and Frische 2000). The four species in this complex (A. achilles Shaw, A. japonicus Schmidt, A. leucosternon Bennett, and A. nigricans) are thought to hybridize when their distributional ranges overlap (Craig 2008). Hybrids have been recorded from the Hawaiian Islands (Acanthurus achilles x nigricans), Taiwan (Acanthurus japonicus x nigricans), Indonesia, Christmas and Cocos Island (Acanthurus leucosternon x nigricans) (Randall 2001a, Marie et al. 2007).|
|Red List Category & Criteria:||Least Concern ver 3.1|
|Assessor/s:||Choat, J.H., Abesamis, R., Clements, K.D., McIlwain, J., Myers, R., Nanola, C., Rocha, L.A., Russell, B. & Stockwell, B.|
|Reviewer/s:||Davidson, L., Edgar, G. & Kulbicki, M.|
Acanthurus nigricans is widespread throughout the Pacific Ocean. It is common and abundant in parts of its range. It is caught incidentally as food and is a component of the marine aquarium trade. Harvest for the aquarium trade is not considered a major threat globally and it occurs in a number of marine reserves in parts of its distribution. It is therefore listed as Least Concern.
Acanthurus nigricans is widely distributed in the Pacific Ocean. In the Pacific Ocean, it occurs from Ryukyu islands and the Great Barrier Reef to the Hawaiian islands and French Polynesia (excluding Rapa). In the eastern Indian Ocean, it is known from Cocos-Keeling Islands and Christmas Island. It was recently recorded from Diego Garcia, Chagos Archipelago (Craig 2008).
This species occurs across the eastern Pacific barrier from the tip of Baja California to the southwest and southeast Gulf of California, southern Mexico, Costa Rica to Ecuador and all the offshore islands.
Native:American Samoa (American Samoa); Australia; British Indian Ocean Territory (Chagos Archipelago); Brunei Darussalam; China; Christmas Island; Cocos (Keeling) Islands; Colombia; Cook Islands; Costa Rica; Disputed Territory (Paracel Is., Spratly Is.); Ecuador (Ecuador (mainland), Galápagos); Fiji; French Polynesia; Guam; Indonesia; Japan; Kiribati (Gilbert Is., Kiribati Line Is., Phoenix Is.); Malaysia; Marshall Islands; Mexico; Micronesia, Federated States of ; Nauru; New Caledonia; Niue; Northern Mariana Islands; Palau; Panama; Papua New Guinea; Philippines; 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; Indian Ocean – western; Pacific – eastern central; Pacific – northwest; Pacific – southeast; Pacific – western central
|Range Map:||Click here to open the map viewer and explore range.|
Acanthurus nigricans is common and widespread throughout the Pacific Ocean. On Christmas Island, it is the dominant Acanthurid on a reef dominated by Acanthurids and achieves mean densities of 83.6 (SE 9.14) per 1,000 m2 (Choat unpub. data). It was at least eightfold more abundant than Acanthurus leucosternon and twofold more abundant than putative hybrids at Cocos (Keeling) and Christmas Island (Marie et al. 2007).
In Fagatale Bay, American Samoa, it is a dominant species on the reef slope (Green et al. 1999). A. nigricans was the second most dominant species recorded from Tutuila, Aunuu, and Taema Banks, American Samoa, contributing to 7.6% of total fish biomass and 11.87% of numerical abundance (Sabater and Tofaeono 2006). In Tutuila Island, American Samoa, it was the second most dominant species recorded, contributing
to 8% of total fish biomass (Sabater and Tofaeono 2007).
It was the fourth most abundant Acanthurid in Guam and Saipan, but makes a minor contribution to the Acanthurid fishery, 2.5% and 0.5% respectively (J. McIlwain unpub. data). This species is collected as an aquarium fish in West Hawaii. The total number of individuals caught from FY 2005-2009 was 3,969 with a total value of $18,813 (Walsh et al. 2010). It is common and locally abundant in the Philippines but is not specifically targeted in the fishery (R. Abesamis and B. Stockwell pers. comm. 2010). It was recorded as generally rare, but locally common, particularly at Louisiades, Milne Bay, Papua New Guinea (Allen 2003). It was recorded as occasional at Raja Ampat, Indonesia (Allen 2003b).
In the central Philippines, density and biomass of herbivorous fish in reserves had positive relationships with duration of reserve protection. Acanthuridae and Labridae (parrotfishes) were the major families that increased in biomass inside reserves with duration of reserve protection. Herbivore biomass inside reserves compared to fished sites was on average 1.4, 4.8 and 8.1 times higher at 0.5 to 4, 5 to 7 and 8 to 11 years of protection, respectively. For A. nigricans, mean biomass recorded in 2 reserves (5 to 7 years duration of protection) were 0.59 and 0.07 (kg per 500 m2) (Stockwell et al. 2009).
This species is the least abundant of the Acanthurids at Gorgona, Colombia. According to Robertson and Allen (1996), this fish was frequent enough to have a resident population in Clipperton Atoll. This fish was studied in the Galapagos archipelago, with an overall mean density of 1.49 ind/500 m2 (Edgar et al. 2004). It is locally common in southern Costa Rica, and in Cano Island and Cocos Island.
According to Aburto-Oropeza and Balart (2001), A. nigricans is a rare species in Los Islotes, Gulf of California, having an occurrence frequency below 10%. In Cabo Pulmo, Gulf of California, this species was considered scarce, with a relative frequency between 25-50% (Villarreal-Cavazos et al. 2000). Densities on the tropical eastern Pacific offshore islands are much higher than along the continental coast.
|Habitat and Ecology:||
This reef-associated species inhabits hard substrate areas of clear lagoons and seaward reefs, from the lower surge zone to at least 67 m. Small juveniles hide among large corals (Kuiter and Tonozuka 2001). In the Gulf of Chiriqui, Panama, this species can be found over exposed shallow rocky reefs and deep rocky walls (Dominici-Arosemena and Wolff 2006). According to Rubio (1986), at Gorgona Island, Colombia, this fish (cited as A. glaucopareius) is abundant on rocky substrata, while also frequently found on sandy and coralline substrata. It grazes on algal turf mainly on thallate and filamentous algae (Choat et al. 2002, Choat et al. 2004). Maximum age was 34 years in the Great Barrier Reef (Choat and Robertson 2002). Mean maximum age for females is 30 years, males at 24 years (Jones 2008).
The sexes are separate among the acanthurids and there is no evidence of sexual dimorphism (Reeson 1983). However, there is size dimorphism with females consistently larger than males (J.H. Choat pers. comm. 2010). Acanthurus nigricans is monogamous (Whiteman and Côté 2004).
There are no major threats known for this species.
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:||There are no species-specific conservation measures in place for this species. Its distribution overlaps several marine protected areas in parts of its range.|
|Citation:||Choat, J.H., Abesamis, R., Clements, K.D., McIlwain, J., Myers, R., Nanola, C., Rocha, L.A., Russell, B. & Stockwell, B. 2012. Acanthurus nigricans. In: IUCN 2013. IUCN Red List of Threatened Species. Version 2013.2. <www.iucnredlist.org>. Downloaded on 11 December 2013.|
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