Overview

Comprehensive Description

Biology

Found over sand and coral bottoms of clear channels (Ref. 9710). Juveniles probably occur on reef flats (Ref. 9710). Rare and not commercial (J.E. Randall, pers. comm.).
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Distribution

Range Description

Acanthurus chronixis is known only from Kapingamarangi Atoll, Caroline Islands. It is reported from southwestern Taiwan and southern Japan, however, reports from other areas are probably misidentifications of the juvenile stages of Acanthurus pyroferus (Randall 2002b, R.F. Myers pers. comm. 2011). The estimated area of occupancy (AOO) is 64 km² using coral layer analysis with the World Conservation Monitoring Centre's 1 km grid polygon.


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Western Pacific: Kapingamarangi Atoll, Caroline Islands. Possibly endemic of that atoll. Reports from other areas are likely misidentifications of the juvenile stages of Acanthurus pyroferus (J.E. Randall, pers. comm.), e.g. from Taiwan (Shao et al., 2008).
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Western Pacific.
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Physical Description

Morphology

Dorsal spines (total): 8; Dorsal soft rays (total): 26; Analspines: 3; Analsoft rays: 24
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Size

Max. size

28.0 cm TL (male/unsexed; (Ref. 37792))
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Diagnostic Description

Caudal fin lunate. Life colour unknown. Preserved specimen is dark brown with two small oval spots, one above and the other slightly behind the upper end of the gill opening, and a dark brown band at the base of the dorsal fin.
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Ecology

Habitat

Habitat and Ecology

Habitat and Ecology
Acanthurus chronixis was described from a single adult specimen collected over coral and sand bottom in less than 6 m (Randall 1960, 2001a). The sexes are separate among the acanthurids and there is no evidence of sexual dimorphism (Reeson 1983).

Systems
  • Marine
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Environment

reef-associated; marine; depth range 0 - 6 m (Ref. 37792)
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Depth range based on 3 specimens in 1 taxon.
Water temperature and chemistry ranges based on 3 samples.

Environmental ranges
  Depth range (m): 1.83 - 17
  Temperature range (°C): 28.793 - 29.282
  Nitrate (umol/L): 0.059 - 0.156
  Salinity (PPS): 34.134 - 34.323
  Oxygen (ml/l): 4.441 - 4.517
  Phosphate (umol/l): 0.092 - 0.163
  Silicate (umol/l): 1.097 - 1.476

Graphical representation

Depth range (m): 1.83 - 17

Temperature range (°C): 28.793 - 29.282

Nitrate (umol/L): 0.059 - 0.156

Salinity (PPS): 34.134 - 34.323

Oxygen (ml/l): 4.441 - 4.517

Phosphate (umol/l): 0.092 - 0.163

Silicate (umol/l): 1.097 - 1.476
 
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Conservation

Conservation Status

IUCN Red List Assessment


Red List Category
VU
Vulnerable

Red List Criteria
D2

Version
3.1

Year Assessed
2012

Assessor/s
Myers, R., Choat, J.H., Abesamis, R., Clements, K.D., McIlwain, J., Nanola, C., Rocha, L.A., Russell, B. & Stockwell, B.

Reviewer/s
Edgar, G., Davidson, L. & Kulbicki, M.

Contributor/s

Justification
Acanthurus chronixis is known from a limited number of specimens: the holotype and two possible juveniles from Kapingamarangi Atoll, Caroline Islands and an individual collected in 1980. The estimated area of occupancy is 31 km² using 25 m depth layer analysis on ArcGIS, however, this species has only been collected in depths no greater than 6 m, so the AOO is much less than 31 km².There is taxonomic work under way to verify the taxonomic standing of this species, as it is involved in species complexes that mimic colour patterns. There is very little information available on the population status or life history characteristics of this species. Kapingamarangi Atoll is a highly isolated but heavily populated island. Local waters are presumably heavily fished with spearfishing occurring widely around the island (G. Edgar pers. comm. 2011). This species is therefore listed as Vulnerable under D2. We recommend continued research on this species' taxonomic standing, distribution, life history characteristics and population status. We accept current taxonomy that this species is valid (Eschmeyer 2011, J.E. Randall pers. comm. 2011) and although taxonomic problems persist for this putative species, it is clear that even at the population level, the only location where it occurs is subject to intensive harvesting.
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Population

Population
There is very limited population information available for this species and this is attributed to its isolated range of distribution. This species was originally only known from the type specimens, however, an individual has been collected since its description in 1960 (accessed through the Fishnet 2 Portal, www.fishnet2.org, 2012-06-11).

Population Trend
Unknown
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Threats

Major Threats
Kapingamarangi Atoll is a highly isolated but heavily populated island. Local waters are presumably heavily fished with spearfishing occurring widely around the island (G. Edgar pers. comm. 2011).

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).
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Vulnerable (VU) (D2)
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Management

Conservation Actions

Conservation Actions
There are no species-specific conservation measures in place. Kapingamarangi Atoll is extremely isolated; the nearest atoll Nukuoro, is 164 nautical miles northward (Niering and Miller 1956).
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Relevance to Humans and Ecosystems

Benefits

Importance

fisheries: of no interest; aquarium: commercial
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Wikipedia

Acanthurus chronixis


Acanthurus chronixis is a tropical fish known commonly as the Chronixis surgeonfish or the Mimic surgeonfish.[2] It was first named by Randall in 1960.[3] The species lives in coral reefs in the western Pacific.[4]

References[edit source | edit]

  1. ^ Myers, R., Choat, J.H., Abesamis, R., Clements, K.D., McIlwain, J., Nanola, C., Rocha, L.A., Russell, B. & Stockwell, B. 2012. Acanthurus chronixis. In: IUCN 2012. IUCN Red List of Threatened Species. Version 2012.2. <www.iucnredlist.org>. Downloaded on 9 January 2013.
  2. ^ Common names for Acanthurus chronixis at www.fishbase.org.
  3. ^ Page 29, Surgeonfishes of the world, by John E. Randall. Mutual Pub., 2001. ISBN 1-56647-561-9/ISBN 978-1-56647-561-7
  4. ^ Acanthurus chronixis at www.fishbase.org.
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