Choerodon

Orange-dotted tuskfish Choerodon anchorago, copyright Rickard Zerpe.

Belongs within: Labridae.

Tuskfish
Published 13 October 2019

The reefs of the Indo-west Pacific Oceans are one of the most species-rich regions of the entire marine environment. A complex geological history and high geographical complexity have contributed to drive speciation, resulting in a number of local radiations. One such radiation is the tuskfishes of the genus Choerodon.

Orange-dotted tuskfish Choerodon anchorago, copyright Bernard Dupont.

Choerodon is a genus of the wrasse family Labridae, most diverse around the islands of south-east Asia and northern Australasia where they inhabit coastal reefs or sea-grass beds. A revision of the genus by Gomon (2017) recognised 27 species, varying in size from a little over ten centimetres in length to half a metre or more. LIke other members of the wrasse family, they are often brightly coloured, with juveniles in particular of a number of species being patterned with bold vertical stripes. The vernacular name of ‘tuskfish’, as well as the zoological name of the genus (which translates as ‘pig-tooth’), refers to the possesion of a pair of prominent, protruding incisors at the front of each of the upper and lower jaws. Other characteristic features of Choerodon include a dorsal fin with twelve spiny rays and eight soft rays, or thirteen spines and seven soft rays, and a lack of scales on the lower part of the cheek and lower jaw. Choerodon species, like most other wrasses, are protogynous hermaphrodites, starting their lives as females before eventually transforming into males.

Baldchin groper Choerodon rubescens, copyright Katherine Cure.

Diet-wise, tuskfishes are predators, feeding on animals such as crustaceans or mollusks. Larger species may even take other vertebrates. A kind of tool use has been observed for the genus, with difficult prey such as clams (Jones et al. 2011) or young turtles (Harborne & Tholan 2016) being grasped in the mouth and hammered against rocks to subdue them and/or break open shells. Multiple species of tuskfish may be found in close proximity though they will often differ in their preferred habitat. A study of five Choerodon species found around Shark Bay in Western Australia by Fairclough et al. (2008) found that the baldchin groper C. rubescens was found only on exposed marine reefs whereas the other four species preferred more sheltered habitats further inside the bay. The blue tuskfish C. cyanodus and blackspot tuskfish C. schoenleinii were both found in a range of habitats in this region but C. cyanodus was most abundant along rocky shores whereas C. schoenleinii preferred coral reefs (C. schoenleinii also differed from other species in the region in constructing burrows at the base of reefs that it used as a retreat). The purple tuskfish C. cephalotes was almost exclusively found among seagrass meadows. Finally, the bluespotted tuskfish C. cauteroma spent the early part of its life among seagrasses but moved onto reefs as it matured to adulthood.

Tuskfish and other wrasses are highly prized as eating fishes. However, it would be remiss to refer to the reefs of the Indo-west Pacific without mentioning that many of them are highly endangered. Heavy fishing, often using destructive methods, have combined with the effects of changing climate to cause a dramatic reduction in reef cover in recent decades. Should the decline continue at current rates, the lives of millions of people stand to be dangerously impacted.

Systematics of Choerodon
<==Choerodon Bleeker 1847S57
    |--C. anchorago (Bloch 1791)S57 (see below for synonymy)
    |--C. albigenaG75
    |--C. cauteroma Gomon & Allen 1987H90
    |--C. cephalotes (Castelnau 1875)MM14
    |--C. cyanodus (Richardson 1843)MM14
    |--C. jordani (Snyder 1908)H90
    |--C. leucozonusJR10
    |--C. meander (Cartier 1873) [=Choerops meander]JR10
    |--C. monostigma Ogilby 1910MM14
    |--C. oligacanthusJR10
    |--C. robustus (Gunther 1866) [incl. Choerops dodecacanthus Bleeker & Pollen 1874]S57
    |--C. rubescens (Günther 1862)H90
    |--C. schoenleinii (Valenciennes 1839) [=Cossyphus schoenleinii; incl. Choerops ommopterus Günther 1880]M58
    |--C. unimaculatus (Cartier 1873) [=Choerops unimaculatus]JR10
    |--C. venustusG75
    |--C. vitta Ogilby 1910MM14
    |--C. zamboangaeJR10
    `--C. zosterophorus (Bleeker 1868) [=Choerops zosterophorus]M58

Choerodon anchorago (Bloch 1791)S57 [=Sparus anchoragoM58, Choerops anchoragoM58; incl. Choerops macrodon Macleay 1883M58, Choerodon macrodonJR10, Labrus macrodontus Lacepede 1802S57, *Choerodon macrodontusS57]

*Type species of generic name indicated

References

Fairclough, D. V., K. R. Clarke, F. J. Valesini & I. C. Potter. 2008. Habitat partitioning by five congeneric and abundant Choerodon species (Labridae) in a large subtropical marine embayment. Estuarine, Coastal and Shelf Science 77: 446–456.

Gomon, M. F. 2017. A review of the tuskfishes, genus Choerodon (Labridae, Perciformes), with descriptions of three new species. Memoirs of Museum Victoria 76: 1–111.

[G75] Grant, E. M. 1975. Guide to Fishes. The Co-ordinator-General’s Department: Brisbane (Australia).

Harborne, A. R., & B. A. Tholan. 2016. Tool use by Choerodon cyanodus when handling vertebrate prey. Coral Reefs 35: 1069.

[H90] Hutchins, J. B. 1990. Fish survey of South Passage, Shark Bay, Western Australia. In: Berry, P. F., S. D. Bradshaw & B. R. Wilson (eds) Research in Shark Bay: Report of the France-Australe Bicentenary Expedition Committee pp. 263–278. Western Australian Museum.

Jones, A. M., C. Brown & S. Gardner. 2011. Tool use in the tuskfish Choerodon schoenleinii? Coral Reefs 30 (3): 865.

[JR10] Jordan, D. S., & R. E. Richardson. 1910. Check-list of the species of fishes known from the Philippine archipelago. Bureau of Printing: Manila.

[MM14] Moore, G. I., S. M. Morrison, J. B. Hutchins, G. R. Allen & A. Sampey. 2014. Kimberley marine biota. Historical data: fishes. Records of the Western Australian Museum Supplement 84: 161–206.

[M58] Munro, I. S. R. 1958. The fishes of the New Guinea region: a check-list of the fishes of New Guinea incorporating records of species collected by the Fisheries Survey Vessel “Fairwind” during the years 1948 to 1950. Papua and New Guinea Agricultural Journal 10 (4): 97–369 (reprinted: 1958. Territory of Papua and New Guinea Fisheries Bulletin 1).

[S57] Smith, J. L. B. 1957. List of fishes of the family Labridae in the western Indian Ocean. Ichthyological Bulletin 7: 99–114.

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