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Choerodon schoenleinii

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Taxonomy [top]

Kingdom Phylum Class Order Family
ANIMALIA CHORDATA ACTINOPTERYGII PERCIFORMES LABRIDAE

Scientific Name: Choerodon schoenleinii
Species Authority: (Valenciennes, 1839)
Common Name(s):
English Blackspot Tuskfish, Bluebone, Green Wrasse

Assessment Information [top]

Red List Category & Criteria: Near Threatened ver 3.1
Year Published: 2004
Date Assessed: 2004-04-30
Assessor(s): Fairclough, D. & Nakazono, A. (Grouper & Wrasse Specialist Group)
Reviewer(s): Cornish, A. & Sadovy, Y. (Grouper & Wrasse Red List Authority)
Justification:
Choerodon schoenleinii is a highly sought after food fish throughout its distribution. It is high on the list of regularly caught species by recreational fishers at surveyed locations in Western Australia and is a prized species in many areas of south-east Asia, including Sabah, Japan and Hong Kong. There has been a severe decline in its abundance in Hong Kong since the 1940s and it is now considered rare in that location (A. Cornish, pers. comm.; Cornish 2003). Choerodon schoenleinii is a large species, reaching up to 100 cm, and it is a monandric protogynous hermaphrodite, with very low numbers of males recorded in Shark Bay, Western Australia (Ebisawa et al. 1995, Fairclough in prep.). Those two studies demonstrated that male fish occur only in the largest size classes, i.e., > ca. 50 cm, and these are commonly the target of fishers, e.g., in Hong Kong (Cornish 2003). Heavy fishing pressure for local and live reef fish trade use would have rapidly reduced the numbers of males in assemblages of this species and would have undoubtedly contributed to its rapid decline in locations such as Hong Kong. It is also considered to be overexploited in Japan (Ebisawa et al. 1995).

Thus, heavy fishing pressure coupled with the large scale use of destructive fishing practices in south-east Asia and overall low abundances in that region (Werner and Allen 2000, Allen and McKenna 2001) put this species at risk in a substantial proportion of its range. Choerodon schoenleinii should be considered to be Near Threatened and it almost meets the criteria for Vulnerable: VU A2cd and/or VU A3cd and/or VU A4cd. This species should be monitored regularly for further evidence of population decline/ or fragmentation and every effort made to obtain information on its fishery, especially in southeastern Asia and Japan.

Regional status:

Australia
Choerodon schoenleinii is widely distributed and is probably not threatened in many areas of Australia due to the remoteness of its northern coastline, where this species occurs. However, individual assemblages in some areas where there is heavy recreational or commercial fishing pressure may be under threat of localised depletions, e.g., Shark Bay, Dampier and Broome in Western Australia and parts of the Great Barrier Reef, Queensland.

SE Asia

Hong Kong
Choerodon schoenleinii fetches the highest prices for any live reef fish caught in Hong Kong. The species is now extremely rare in Hong Kong, e.g., three seen in roughly 750 dives throughout Hong Kong waters since 1995, (Cornish, pers. comm. 2004) and while it has long been commercially extinct, it was abundant enough in the 1940s to support a small dedicated fishery using longlines with sea-urchins as bait (Cornish 2003).

Malaysia
"Usually dwells in the vicinity of coral reefs, common length 28.6 cm. Not a commercial fish as it does not have a good reputation as a food fish in Peninsular Malaysia. Highly priced in Sabah. Some people like the larger fishes which are highly esteemed in Hong Kong" (Mohsin and Ambak 1996).

Other
Choerodon schoenleinii is most likely to be threatened in areas of south-east Asia, e.g., the Ryukyu Islands (Ebisawa et al. 1995), the Philippines, Indonesia and Papua New Guinea, since C. schoenleinii is a commercial target in many of these areas and methods such as explosives, poisoning, spearfishing and night-time fisheries, are commonly used to capture fish. Many of these countries have used these methods for a long period of time and thus not only localised population declines are likely, but also the destruction of important habitats on a broader scale (TRACC 2004). It is valued eating fish and one of the best among the wrasses for its flesh (A. Nakazono, pers. comm.).

The Live Reef Food Fish Trade
Although not among the 13 most common species in the trade which sources reef fishes from the Indo-Pacific for export primarily to Hong Kong (China), this species is nonetheless included in the lucrative and large international live fish trade (Lee and Sadovy 1998, Sadovy et al. 2003). Although import quantities are not available for this species alone, except for the occasional record (e.g., at least 60.5 kg was brought into Hong Kong in May 2000 by live fish vessel: Clarus Chu, pers. comm.), substantial numbers of C. schoenleinii are included in the trade at sizes generally of 25–40 cm, probably less than that at which sexual maturity is attained (A. Cornish, pers. comm. 2004).

Geographic Range [top]

Range Description: Choerodon schoenleinii occurs as far south on the Western Australian coast as the Houtman-Abrolhos Islands (a group of islands and reefs ca. 70 km offshore at ca 28°45'S, 113°45'E), however, it is considered to be rare at this location (Hutchins 2001). Choerodon schoenleinii was not recorded on inshore coastal reefs south of Shark Bay (ca. 26°S, 113.5°E) during the surveys of Hutchins (2001). Surveys by Hutchins (2001, 2003) and Newman et al. (2003) demonstrate that C. schoenleinii occurs along the northern Pilbara/Kimberley coastline of Western Australia as far north as Wyndham (15°29'S, 128°7'E), but not on the offshore atolls along this coast, i.e., Rowley Shoals, Scott Reef and Ashmore reef. Choerodon schoenleinii is a target for commercial fishers, fishing tour operators and recreational fishers in Darwin, Northern Territory, and is thus probably widespread in this region (P. de Lestang, Northern Territory Government, pers. comm.). It is taken by recreational and commercial fishers along the Queensland coastline, in particular the Great Barrier Reef, where this species is widely distributed (Grant 1993; J. Platten, EPA Queensland, pers. comm.). Choerodon schoenleinii is likely to occur throughout south-east Asia, such as the Philippines and the Ryukyu Islands, where it is a commercial target (Westneat 2004, Ebisawaiet al. 1995). It is probably equally well distributed throughout the rest of its range, e.g., along the Viet Nam and Thailand coastlines, around Malaysia, Indonesia, Irian Jaya, Papua New Guinea and south to Vanuatu, where it is also reported to occur (Eli 2002, Allen and Adrim 2003). Many of these areas provide suitable habitats for this species. A report of C. schoenleinii occurring in Mauritius must be treated with some caution, since there is no evidence of it occurring between Mauritius and south-east Asia (Eli 2002).
Countries:
Native:
Australia (Northern Territory, Queensland, Western Australia); Brunei Darussalam; Cambodia; China; Hong Kong; Indonesia (Jawa, Kalimantan, Lesser Sunda Is., Maluku, Papua, Sulawesi, Sumatera); Japan (Nansei-shoto); Malaysia (Peninsular Malaysia, Sabah, Sarawak); New Caledonia; Papua New Guinea; Philippines; Singapore; Solomon Islands; Taiwan, Province of China; Thailand; Timor-Leste; Vanuatu; Viet Nam
FAO Marine Fishing Areas:
Native:
Indian Ocean – eastern; Indian Ocean – western; Pacific – northwest; Pacific – western central
Range Map: Click here to open the map viewer and explore range.

Population [top]

Population: Australia
Choerodon schoenleinii is abundant in many areas of Shark Bay, Western Australia (Fairclough in prep.), and Hutchins (2001) demonstrated that densities ranged from occasional to abundant at locations northwards from Ningaloo reef to Wyndham (15º29'S, 128º7'E). This species is probably equally abundant along the coastlines of the Northern Territory and Queensland, Australia, since this species is distributed across the whole of the northern half of Australia and commercial and recreational catches of C. schoenleinii in the Northern Territory and Queensland are low to moderate (Penn 2002; P. de Lestang, Northern Territory Government, pers. comm.; J. Platten, EPA Queensland, pers. comm.). Its 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 (Hutchins 2001, Grant, 1993). However, the degree of fragmentation of its distribution and levels of abundance in the Northern Territory of Australia are unclear.

SE Asia
Throughout south-east Asia, the distribution of C. schoenleinii is probably widespread, since coastal reef habitats are virtually ubiquitous in this region. For example, it was reported to occur from Papua to Sumatra in Indonesia by Allen and Adrim (2003). However, it is rarely reported as being common, e.g., C. schoenleinii was reported to be rare with only sub-adults seen during a rapid biodiversity assessment of the Calamianes Islands (Palawan Province, Philippines) (Werner and Allen 2000) and was not seen at all during similar surveys of the coral reefs of Milne Bay, Papua New Guinea (Werner and Allen 1998), the Raja Ampat Islands, West Papua, Indonesia (McKenna et. al. 2002), or the Togean and Banggai Islands, Sulawesi, Indonesia (Allen and McKenna 2001). This may be due to fragmentation of the populations of C. schoenleinii caused by naturally low abundances and/or localised stock depletions due to fishing pressure and destruction of habitat. The latter may be fairly widespread. For example, in Sabah, Borneo, and Indonesia, fishing pressure is concentrated in the inshore region of the coastline and destructive collection methods have depleted most of the inshore fish stocks (TRACC 2004). Destruction of coral reef habitat is also likely to be a contributing factor (see Threats).

In Okinawa, Japan, and Hong Kong C. schoenleinii is/was a very important commercial species and is suggested to be overexploited (Ebisawa et. al. 1995, Cornish 2003).
Population Trend: Unknown

Habitat and Ecology [top]

Habitat and Ecology: Choerodon schoenleinii is a demersal species and is abundant in shallow water reefs in waters of north-western Australia and along the Queensland coast (< 20 m) (Allen 1999, Hutchins 2001, Grant 1993, Randall et. al. 1997, Fairclough, in prep). It is, however, reported to occur in waters up to 60 m deep (Westneat 2004). It is found on sand and weed areas adjacent to coral reefs (Grant 1993, Randall et. al. 1997, Allen 1999). In Shark Bay, Western Australia, it is found on rocky limestone reefs, weedy rock areas, rocky shorelines and seagrass areas (Travers and Potter 2002, Fairclough in prep.). In particular, limestone and coral patch reefs are important for adults of this species in Shark Bay (Fairclough, in prep.). Juveniles (< ca. 150 mm) are found in weedy rock or seagrass habitats, but fish above this size are more common on open reefs in Shark Bay, for example (Travers and Potter 2002, Fairclough, in prep.). Kanashiro (1998) demonstrated that seagrass beds were important for this species during the first few months of life with the presence of larvae and small juveniles in these habitats at Yagachi Island, Japan.

Choerodon schoenleinii reaches lengths of up to 100 cm and ca. 16 kg in weight (Grant 1993). It is a protogynous hermaphrodite and is an indeterminate multiple spawner (Ebisawa et. al. 1995, Fairclough in prep.). Fifty percent of females mature at ca. 25 cm and it spawns mainly in spring in both Shark Bay, Western Australia, and at Okinawa Island, Japan (Ebisawa et. al. 1995, Fairclough, in prep.). Histology demonstrated that this species is monandric and that relatively small testes indicate that male fish would spawn with only one to a few females at once (Ebisawa et. al. 1995, Fairclough in prep). Males only occur in the upper size classes (> ca. 50 cm) and low numbers of males recorded in the population in Shark Bay and at Okinawa Island, Japan, also suggest that this species would be haremic (Ebisawa et. al. 1995, Fairclough, in prep.). Since catch rates derived from line fishing or densities derived from visual surveys in Shark Bay demonstrated little variation during the different months of the year (Fairclough, in prep.), it is unlikely that this species forms large spawning aggregations.
Systems: Marine

Threats [top]

Major Threat(s): A minimum legal size of 40 cm and a catch limit of four tuskfish per person per day in the west coast and Gascoyne regions of Western Australia limits the capture of C. schoenlenii in those two regions (Department of Fisheries Western Australia 2003a, b). 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 on Western Australian stocks. In the northern 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 catch limit regulations for the Pilbara/Kimberley region are currently under review and thus may change in 2004 to fall in line with the west coast and Gascoyne regions of W.A.

In Shark Bay, Western Australia, for example, only a relatively few fish > 40 cm, the minimum legal length for retention, are captured by line fishing, thus reducing the impact of fishing on this species in that embayment (Fairclough in prep.). Records of catches of recreational fishers in Western Australia indicate that C. schoenleinii is regularly one of the top ten species caught from areas of the northern Pilbara/Kimberley region of Western Australia, e.g., Dampier and Broome (Newman et. al. 2003). Thus, there may be the potential for localised depletions of this species in areas of Western Australia, where commercial and/or recreational fishing pressure is high. Catches of the combined tuskfish and parrotfish category in the Northern Territory and Queensland are low, hence it is unlikely to be under widespread threat in these regions (P. de Lestang, Northern Territory Government, pers. comm., J. Platten, DPIF Queensland, pers. comm.). However, it is specifically targeted by recreational fishers in Moreton Bay, Queensland, which may have a localised impact on this species’ abundance (Grant 1993).

There is little specific information on the level of exploitation of this species throughout south-east Asia. However, Ebisawa et. al. (1995) states that C. schoenleinii is an important commercial species in Okinawa, Japan, and that it is overexploited. The majority of C. schoenleinii caught in this region range in length from 20 to 35 cm and thus, based on studies of the reproductive biology of this species, many captured fish are likely to be sexually immature (Ebisawa et. al. 1995, Fairclough in prep.).

Destructive fishing practices, e.g., explosives, spearfishing, poisoning and night-time fishing, used in many parts of south-east Asia to capture fish for local consumption, the live reef fish trade and the aquarium trade, are likely to cause, or may already have caused, declines in stocks of C. schoenleinii in these areas (Munday and Allen 2000, Chou et. al. 2002, Wabnitz et. al. 2003, TRACC 2004). However, there is little data to suggest how much C. schoenleinii contributes to these fisheries. Furthermore, any continued destruction of habitats will lead to further fragmentation of stocks and ultimately to their decline. Land clearing, and thus sedimentation from increased run-off, and poor sanitation in south-east Asian countries, such as Papua New Guinea and the Philippines, also have the potential to destroy important nearshore habitats (Munday and Allen 2000, Chou et. al. 2002). In south-east Asia, it has been estimated that 56 % of all coral reefs are at high risk, and 26% are of medium risk from human disturbance (Bryant et. al. 1998).

Conservation Actions [top]

Conservation Actions: A minimum legal length (MLL) of 40 cm and a catch limit of four tuskfish per person per day in the west coast and Gascoyne regions of Western Australia limits the capture of C. schoenlenii in those two regions (Department of Fisheries Western Australia 2003a, b). 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 on Western Australian stocks. In the northern 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 catch limit regulations for the Pilbara/Kimberley region 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 WA where C. schoenleinii occurs, to reflect increased knowledge of the biology of this species (Fairclough in prep.), the catch limit is unlikely to change from four fish per person per day, unless it is reduced further. 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). There is also a MLL of 30 cm in Queensland and a catch limit of six tuskfish per person per day. However, in the Northern Territory, while there is a catch limit for recreational fishers, there is no MLL.

In Shark Bay, Western Australia, several small sanctuary (no take) zones, i.e., Surf Point, Mary Anne Island, Gudrun Wreck and Sandy Point, are likely to encompass habitats occupied by C. schoenleinii (Anonymous 1996, Fairclough in prep.). There are eight no take sanctuary zones within the Ningaloo Reef Marine Park. Spearfishing of tuskfish is prohibited throughout the marine park (Anonymous 2004). Proposals are currently being considered for new marine parks on the north-west coast of Western Australia (Penn 2002), including the Dampier Archipelago and the Montebello Islands, where C. schoenleinii was recorded frequently during surveys by Hutchins (2001). Marine Parks in Western Australia do not necessarily imply no-take zones, but may include no take zones within their boundaries or restrictions on catch limits or methods used for capture.

In Queensland, there is a minimum legal length for retention of 30 cm and a catch limit of six fish per person per day (Department of Primary Industries and Fisheries 2003). Approximately 5.1 million hectares of Queensland marine waters are declared marine parks and, of this, 603,000 hectares are fish habitat areas, where fishing is allowed, but the habitat is protected from development (Anonymous 2000). These areas stretch along the entire Queensland coastline (Anonymous 2000). It is likely that C. schoenleinii occurs in at least several of these protected areas. 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. schoenleinii occurs in several of these protected areas.

While many marine parks have been introduced in areas within the range of C. schoenleinii, e.g., Papua New Guinea, Indonesia and the Philippines, most of these are considered to be ‘paper parks’ and are 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 MPAs probably provide little protection to the species they house (Licuanan and Gomez 2000, Chou et al. 2002).

Local fishermen in Okinawa started a regulation not to catch this species smaller than 1 kg (A. Nakazono, pers. comm.).

Citation: Fairclough, D. & Nakazono, A. (Grouper & Wrasse Specialist Group) 2004. Choerodon schoenleinii. The IUCN Red List of Threatened Species. Version 2014.3. <www.iucnredlist.org>. Downloaded on 22 December 2014.
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