Justification
Choerodon cauteroma has been recorded to 43.3 cm in length (B. Hutchins, Western Australian Museum, pers. comm.). This species has high quality white flesh and is captured by commercial and recreational fishers in the north-western regions (Gascoyne and Pilbara/Kimberley) of Western Australia (W.A.). It is marketed in Perth, either as whole fish or fillets, and labeled as "baby groper" after its commercially sought-after congeneric, the Baldchin Groper Choerodon rubescens (D. Thorburn, Seafresh Fish Markets, pers. comm.).
Changes to fishing regulations for tuskfish in 2003 for the west coast and Gascoyne coast regions of Western Australia (W.A.) limit their capture to fish ≥ 40 cm in length (total length) and to a maximum of four fish per person per day (for recreational fishers). Since C. cauteroma rarely reaches more than 40 cm in length, these regulations essentially protect this species from capture in those two regions. Regulations for the Pilbara/Kimberley region of W.A. are currently under review and thus may change in 2004 to fall in line with the west and Gascoyne regions of W.A. In the Pilbara/Kimberley region there is currently no minimum legal length for C. cauteroma and the catch limit for recreational fishers is 8 fish per person per day.
Choerodon cauteroma should be considered Least Concern due to the minimum size limit for tuskfish species of 40 cm in Western Australia. This essentially protects this species from capture, since it rarely reaches this size, however, changes to regulations may occur in the future to reflect increased knowledge of the biology of this species (Fairclough in prep.). Since this species has a relatively limited range, it should be reassessed in the future for any changes in commercial or recreational catch composition, particularly if fishing regulations change or if an export market develops, that may ultimately have undesirable impacts on the population structure.
Geographic Range Information
Choerodon cauteroma occurs on coastal and inshore reefs between the Houtman–Abrolhos Islands (a group of islands and reefs ca 70 km offshore at ca 28º45'S, 113º45'E), on the west coast of Australia and the Dampier Peninsula (16º23'S, 122º55'E), on the north-west coast (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. cauteroma 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).
One individual specimen was sighted in a fish market in Jakarta, Indonesia (W. White, Murdoch University, pers. comm.), however, this specimen may have been captured in waters closer to the Australian mainland.
Population Information
Choerodon cauteroma is abundant in Shark Bay (Hutchins et al. 1995, Hutchins 2001, Fairclough et al. unpubl. data). Visual surveys in South Passage, at the southern end of Dirk Hartog Island, Shark Bay, the eastern coastlines of Bernier and Dorre Islands, and sites in the eastern and western gulfs of Shark Bay suggest that C. cauteroma is abundant in these areas (Hutchins 1990, Hutchins 2001, Travers and Potter 2002, Fairclough in prep.). Surveys by Hutchins (2001) demonstrated that C. cauteroma was occasionally or frequently observed at sites between Shark Bay and the Dampier Archipelago and that it was frequently observed at sites on the Dampier Peninsula, but was not recorded to the east of that peninsula. Furthermore, it was not recorded at any of the offshore atolls surveyed, i.e., Rowley Shoals, Scott Reef and Ashmore reef. Research sampling by Fisheries Western Australia using traps and trawl nets along the north-west (Pilbara/Kimberley) coast of Australia collected moderate numbers of C. cauteroma, suggesting a fairly continuous distribution along this coast (Newman et al. 2003). Catches declined rapidly only a short distance north of Broome, which is in agreement with the results of the surveys of Hutchins (2001).
Choerodon cauteroma does not occur in catches of tuskfish species in the Northern Territory (P. de Lestang, Northern Territory Government, pers. comm.).
Habitat and Ecology Information
Choerodon cauteroma is a demersal species and is common in shallow waters (< 15 m). However, it has been captured in waters up to 30 m deep (Newman et al. 2003). It is most abundant on rocky platform reefs, coral reefs and on sand or rubble areas associated with rocky or coral reefs (Hutchins et al. 1995, Allen 1999, Hutchins 2003, Fairclough in prep.). In Shark Bay, juveniles and adults are found on seagrass beds (Travers and Potter 2002, Fairclough et al. unpubl. data). Small juveniles (< ca 150 mm) use weedy rock or seagrass habitats as nursery areas and generally move onto reefs after the first 1–2 years of life, where they mature (Fairclough in prep.). Some adults remain or may move between seagrass and reef areas (Fairclough in prep.).
C. cauteroma is a protogynous hermaphrodite and is an indeterminate multiple spawner. It spawns between April and November in Shark Bay, although spawning fish are most abundant between September and November, i.e., spring (Fairclough in prep.). Relatively small male gonads indicate that male fish would spawn with only one to a few females at once. Spawning fish have been collected in the many individual reef 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, as is typical of many labrids (Fairclough in prep.).
Threats Information
Changes in commercial and/or recreational fishing pressure are the main threats to this species. However, there is no information on the level of exploitation of this species in Western Australia. Historical data on commercial catches in reports of the Department of Fisheries Western Australia combine all tuskfish species as one group, i.e., tuskfish, other than Choerodon rubescens. Thus, the contribution by C. cauteroma to these catches is unknown. Catches of tuskfish between 1994/95 and 1998/99 ranged from 16 to 34 t per year (Research Services Division 2000).
Use and Trade Information
Conservation Actions Information
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. cauteroma to fish ≥ 40 cm in length (total length) and to a maximum of four fish per person per day (for recreational fishers) (Department of Fisheries Western Australia 2003a, b). Since C. cauteroma 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. Thus, the MLL for this species may be changed once the results of Fairclough (in prep.) become available.
In the Pilbara/Kimberley region of W.A., there is currently no MLL for retention of C. cauteroma and 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 and Gascoyne regions of W.A.
Although, in the future, the MLL may change in all regions of W.A. where C. cauteroma occurs, to reflect more knowledge of the biology of this species, 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 Shark Bay, four sanctuary (no take) zones, i.e., South Passage, Mary Anne Island, Sandy Point and the Gudrun wreck, encompass habitats occupied by C. cauteroma (Anonymous 1996, Hutchins 1990, Fairclough in prep.). There are eight no take sanctuary zones within the Ningaloo Reef Marine Park. Spearfishing of tuskfish is prohibited throughout this marine park (Anonymous (2004).
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 C. cauteroma is found (Hutchins 2001, 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.
