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Choerodon cyanodus

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Taxonomy [top]

Kingdom Phylum Class Order Family
ANIMALIA CHORDATA ACTINOPTERYGII PERCIFORMES LABRIDAE

Scientific Name: Choerodon cyanodus
Species Authority: (Richardson, 1843)
Common Name(s):
English Bluebone Groper, Blue Tuskfish

Assessment Information [top]

Red List Category & Criteria: Least Concern ver 3.1
Year Published: 2004
Date Assessed: 2004-04-30
Assessor(s): Fairclough, D., Russell, B. & Kulbicki, M. (Grouper & Wrasse Specialist Group)
Reviewer(s): Sadovy, Y. & Cornish, A. (Grouper & Wrasse Red List Authority)
Justification:
Choerodon cyanodus is abundant along the northwest coast of Western Australia (W.A.) (Hutchins 2001). It is a recreational and possibly a commercial target in W.A., although it is not a widely captured species, since it rarely reaches the current minimum legal total length for capture of 40 cm in that state (Fairclough in prep., Newman et al. 2003, Department of Fisheries Western Australia 2003a,b,c). Annual commercial catches of tuskfish are reported as a combined category, i.e., "tuskfish", not as individual species in Western Australia. Choerodon cyanodus is recognized as a recreational target in Queensland, however, less so than its congeneric Choerodon venustus, and catches are suggested to be low (J. Platten, EPA Queensland, pers. comm.). Commercial catches of labrids and scarids in Queensland are grouped as ‘parrots’, hence the total catch levels of C. cyanodus in this region are unclear, but are likely to be low (J. Platten, EPA Queensland, pers. comm.). Levels of exploitation in Australia are thus likely to be low.

Levels of abundance and commercial or recreational exploitation in other areas of the distribution of C. cyanodus are unclear. Catch statistics are not available for many countries throughout south-east Asia. However, with destructive methods, such as explosives and poisons, used commonly in areas such as the Philippines, Indonesia and Papua New Guinea, the occurrence of localized depletions may be widespread (Chou et al. 2002).

As the majority of the global population of C. cyanodus is likely to be in Australia (see Range below), this global assessment is based primarily on the situation there. Since annual catches of C. cyanodus are low throughout Australia and suitable fishing regulations are in place, this species would be considered least concern in that country. Furthermore, although its distribution is suggested to be wide in south-east Asia (Allen 1999), other studies do not report the occurrence of C. cyanodus in many areas of that region, e.g., Masuda et al. 1984, Monkolprasit et al. 1997, Werner and Allen 1998, Allen and Adrim 1993, and thus records of this species in those regions are likely to be erroneous or it is of low abundance. While fishing or major habitat loss (in SE Asian areas of its distribution) may be responsible for some population decline, it is not expected to be 30% or greater, or to get much worse in the foreseeable future,, and therefore this species does not meet any of the threatened criteria and should be considered least concern on a global scale.

Geographic Range [top]

Range Description: In Western Australia, Choerodon cyanodus occurs as far south as the Houtman-Abrolhos Islands (a group of islands and reefs ca. 70 km offshore at ca. 28º45'S, 113º45'E), however, it is considered to be rare at this location (Hutchins 2001). The Houtman-Abrolhos Islands is in the vicinity of the path of the southward-flowing Leeuwin Current (Hatcher 1991). This current carries the eggs and larvae of tropical species southwards along the Western Australian continental shelf (Hutchins 1991). The Leeuwin current is likely to be the main reason for individuals of C. cyanodus being recorded in the Abrolhos Islands, since it is considered to be rare at this location and this species was not recorded by Hutchins (2001) during surveys of inshore coastal reefs south of Shark Bay (ca. 26ºS, 113.5ºE) (Hutchins 2001).

Surveys by Hutchins (2001, 2003) and Newman et al. (2003) demonstrate that C. cyanodus occurs along the northern Pilbara/Kimberley coastline of Western Australia as far north as Wyndham (15º29'S, 128º7'E), but not on the offshore atolls along this coast, i.e., Rowley Shoals, Scott Reef and Ashmore reef. While this species’ distribution is reported to extend along the coastline of northern Australia, data suggests that fishing tour operators in Darwin do not catch C. cyanodus (P. de Lestang, Northern Territory Government, pers. comm.). However, tuskfish in commercial catches are often combined and labeled ‘parrots’ in this region. Choerodon cyanodus occurs along the Queensland coastline around the Gulf of Carpentaria, Cape York Peninsula and on the Great Barrier Reef, and has previously been studied at Heron Island (Choat, 1969). Choat (1969) suggests that this species occurs as far south as ca. 24ºS on the east coast of Australia.

Choerodon species reported to occur in Sri Lanka by the FAO do not include C. cyanodus, however, if it does occur in this area as suggested by Allen (1999), it seems likely to be present only in low numbers or in restricted areas and this would represent the westerly limit of its distribution (De Bruin et al. 1994). Choerodon cyanodu is also reported by divers to occur along the Thailand coastline (Anonymous 2004a) but does not appear in extensive lists of species from that country (Monkolprasit et al. 1997), or other areas outside Australia where it is reported to occur, notably Indonesia (Papua to Sumatra; Allen and Adrim 2003), Japan (Masuda et al. 1984) and Milne Bay, Papua New Guinea (Werner and Allen 1998). It appears that either records of this species outside Australia, are largely in error, or abundance in these areas is very low. This global assessment is, therefore, based primarily on populations in Australia which are likely to comprise the majority of the global population.
Countries:
Native:
Australia (Northern Territory, Queensland, Western Australia); Papua New Guinea
FAO Marine Fishing Areas:
Native:
Indian Ocean – eastern; Pacific – northwest; Pacific – western central
Range Map: Click here to open the map viewer and explore range.

Population [top]

Population: Choerodon cyanodus is rare at the Houtman-Abrolhos Islands, which represent the lower limit of this species’ distribution in Western Australia (Hutchins 2001). Surveys by Hutchins (2001, 2003) and research sampling by Newman et al. (2003) found this species to be abundant at locations northwards from the north west cape of Western Australia, however, Fairclough (in prep.) found that this species was also abundant in many areas of Shark Bay to the south.

It is probably equally abundant along the Queensland coastline as this area is well within its geographic range, and since it does not feature prominently in commercial or recreational catches (J. Platten, EPA Queensland, pers. comm.). Distribution along the western and eastern coastlines of Australia is likely to be fairly continuous within its range, due to similar habitat being available throughout. The degree of fragmentation of its distribution and levels of abundance in the Northern Territory of Australia and throughout the remainder of its geographic range in south-east Asia are unclear.
Population Trend: Unknown

Habitat and Ecology [top]

Habitat and Ecology: Choerodon cyanodus is a demersal species and is abundant in shallow waters in Shark Bay (< 10 m). It has been captured in waters up to 30 m deep along the Pilbara/Kimberley coast of Western Australia (Newman et al. 2003). It is found on flat bottoms and coral reefs (Allen 1999). However, it is common on rocky limestone reefs, weedy-rock areas, rocky shorelines and seagrass areas in Shark Bay (Travers and Potte 2002, Fairclough, in prep.). Juveniles and adults (< ca. 200 mm) are found in weedy rock or seagrass habitats, but fish above this size are more common on reefs or rocky habitats (Fairclough in prep.). While records suggest that this species reaches 70 cm in length and recreational fishing records suggest a specimen weighing 4.5 kg was captured in Shark Bay (Australian Anglers Association, (WA Division) Inc. 2003), the majority of fish collected in Shark Bay during current research were below 30 cm and none were collected above 40 cm (Fairclough, in prep.). All fish collected by Choat (1969) from the Great Barrier Reef were < 405 mm in length. Mature fish of ca. 100–150 mm have been collected in seagrass and weedy rock habitats, implying that this species may not always migrate to reefs after maturity and it may live its full lifecycle in either seagrass or reef habitats (Fairclough, in prep.).

Choerodon cyanodus is a protogynous hermaphrodite and is an indeterminate multiple spawner. It spawns between December and February in Shark Bay, i.e., summer (Fairclough, in prep). Relatively small male gonads indicate that male fish would spawn with only one to a few females at once. Mature and spawning fish have been collected in the many individual reef and seagrass habitats occupied by this species in Shark Bay and it is unlikely that this species forms large spawning aggregations, but more than likely spawns in small groups (Fairclough, in prep.).
Systems: Marine

Threats [top]

Major Threat(s): There is no direct information on the level of exploitation of this species throughout most of its range. A minimum legal length of 40 cm in Western Australia virtually prevents its capture, since fish caught during research in both Shark Bay and on the northwest coast of Western Australia were always under this size (Department of Fisheries Western Australia 2003a,b,c, Fairclough in prep., Newman et al. 2003). Catches of the combined "tuskfish" category in Western Australia are moderate (16 to 34 t per year between 1994/95 and 1998/99; Research Services Division 2000), but, since C. cyanodus is rarely larger than its MLL, it is unlikely to be significant in these catches. Although C. cyanodus is a recognized target for recreational fishers in Queensland, it is only caught in small numbers (J. Platten, EPA Queensland, pers. comm.) and commercial catches of the combined category of ‘parrots’ (Labrids and Scarids) in that state are around 30 t per year, consisting mainly of Choerodon venustus, C. cyanodus is unlikely to be threatened on the east coast of Australia (J. Platten, EPA Queensland, pers. comm.). Choerodon cyanodus is not taken in the Northern Territory of Australia (P. de Lestang, Northern Territory Government, pers. comm.).

Destructive fishing practices used to capture fish for local consumption, the live reef fish trade and the aquarium trade in many parts of south-east Asia, may represent the largest threat to C. cyanodus (Munday and Allen 2000, Wabnitz et al. 2003, Chou et al. 2002). However, there is no data to suggest whether C. cyanodus forms a part of any of these industries. Land clearing, and thus sedimentation from increased run-off, and poor sanitation in southeast Asian countries, such as Papua New Guinea and the Philippines, also have the potential to destroy important habitats (Munday and Allen 2000, Chou et al. 2002).

Conservation Actions [top]

Conservation Actions: There are minimum legal lengths (MLL) for capture of C. cyanodus in Western Australia and Queensland of 40 and 30 cm, respectively, however, there are no such limits in the Northern Territory. Changes to fishing regulations for tuskfish in 2003 for the west coast and Gascoyne coast regions of Western Australia (W.A.) limit the capture of C. cyanodus to a mixed bag of four tuskfish per person per day (for recreational fishers) (Department of Fisheries Western Australia 2003a). Since C. cyanodus rarely reaches more than 40 cm in length (Fairclough in prep.), these regulations essentially protect this species from capture in those two regions. However, the minimum legal length (MLL) of 40 cm has not been set based on any knowledge of the biology of this species, since there is currently no information published. In the Pilbara/Kimberley region of W.A. the catch limit for recreational fishers is 8 fish per person per day (Department of Fisheries Western Australia 2003c). These regulations are currently under review and thus may change in 2004 to fall in line with the west coast and Gascoyne regions of W.A.

Although, in the future, the MLL may change in all regions of W.A. where C. cyanodus occurs, to reflect more knowledge of the biology of this species (Fairclough in prep.), the catch limit is unlikely to be increased, since these limits are based on the type of life history that a particular species has. Thus, tuskfish are included in the category of "highest risk" (Harrison 2001). Species in this category are generalised as having the following characteristics: they are long-lived, slow-growing, they mature at four years plus, form semi-resident populations, are vulnerable to localised depletion due to their life history, or are of low abundance or highly targeted (Harrison 2001).

In the Northern Territory and Queensland there are catch limits for recreational fishers of 30 and six fish per person per day, respectively. Since this species is not taken in the Northern Territory and catches are low in Queensland (P. de Lestang, DPIF Northern Territory, pers. comm., J. Platten, EPA Queensland, pers. comm.), this species is well protected in these two states of Australia.

In Western Australia, several small sanctuary (no take) zones, i.e., Surf Point, Mary Anne Island, Gudrun Wreck and Sandy Point, in Shark Bay, are likely to encompass habitats occupied by C. cyanodus (Anonymous 1996, Fairclough in prep.). There are eight no take sanctuary zones within the Ningaloo Reef Marine Park. Spearfishing of tuskfish is prohibited throughout that park (Anonymous 2004b). Proposals are currently being considered for new marine parks on the north-west coast of Western Australia, including the Dampier Archipelago and Montebello Islands, where it is likely that C. cyanodus is found (Penn 2002). Marine Parks in Western Australia do not necessarily imply no take zones, but may include no take zones within their boundaries or restrictions on bag limits or methods used for capture.

In Queensland, approximately 5.1 m hectares are declared marine parks and of that 603,000 hectares are fish habitat areas, where fishing is allowed, but the habitat is protected from any development (Anonymous 2000). These areas stretch along the entire Queensland coastline (Anonymous 2000). In the Great Barrier Reef Marine Park, a proposed rezoning plan will result in ca 33% of the geographical area of the park being designated as no take zones (GBRMPA 2003). It is likely that C. cyanodus occurs in several of these protected areas.

While marine parks have been introduced in areas within the range of C. cyanodus, e.g., Sri Lanka, Papua New Guinea and the Philippines, most of these are considered to be ‘paper parks’ and are thus poorly managed or legislation is poorly enforced. Only 8% of the 100,000 km² of coral reefs in southeast Asia is included in marine protected areas and only 14% of the 646 MPAs are considered effective, hence the majority of these marine parks probably provide little protection to the species they house (Chou et al. 2002, Licuanan and Gomez 2000).

Citation: Fairclough, D., Russell, B. & Kulbicki, M. (Grouper & Wrasse Specialist Group) 2004. Choerodon cyanodus. The IUCN Red List of Threatened Species. Version 2014.2. <www.iucnredlist.org>. Downloaded on 25 July 2014.
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