Blackspot tuskfish (Choerodon schoenleinii)
|Also known as:||Bluebone and green wrasse|
|Size||Maximum length: 100 cm (2)|
|Weight||15.5 kg (3)|
The blackspot tuskfish is classified as Near Threatened (NT) on the IUCN Red List (1).
The blackspot tuskfish (Choerodon schoenleinii) is the largest species of tuskfish, and is named for the distinctive black spot found just below the final dorsal spine (3). Tuskfish are well-known for their obvious canines, and the blackspot tuskfish has four curved canines in each jaw (4) (5). In the upper jaw, the front pair of canines is longer than the outer pair (4).
The female blackspot tuskfish is generally green-yellow, while the male is blue (2). The back is greenish-grey and the underparts are pale yellowish (3). A single blue line runs from the eye to the upper lip (4) (5) and the pectoral, dorsal and anal fins are a greyish-green with blue stripes (5).
Each scale has a distinctive blue stripe, except for the scales on the narrow section of the body adjoining the tail, which have blue spots merging to form stripes (3) (5). The tail is short and slightly rounded (5).
The blackspot tuskfish is found throughout the coastal waters of south Asia, Indonesia and Australia (6). Sightings have been reported in the waters off Mauritius, but these have yet to be verified (1).
This fish is known to reside in ocean reefs and reefs in lagoons (3). The adult blackspot tuskfish prefers weedy or flat sandy areas (6) and juveniles can be found in seagrass habitats (2). It is commonly found at depths of 10 to 20 metres (3), but the maximum depth range is about 60 metres (6) (7). The blackspot tuskfish may also rest in caves at night (2).
The blackspot tuskfish is usually a solitary species, but it can also be found in small groups (2). It feeds mainly on hard-shelled invertebrates such as molluscs, urchins and crustaceans (7), upturning large rocks in attempts to expose prey (2) (3).
Although the blackspot tuskfish may be seen resting on the sea floor during the day(6), a tracking studyconducted on released hatchery-reared blackspot tuskfish suggests that it is more active during the day than at night (8).
The minimum size for sexual maturity is 24 centimetres in length, and the blackspot tuskfish is aprotogynous hermaphrodite, changing sex from female to male when it reaches a total length of 40 to 64 centimetres (2). In some areas, male blackspot tuskfish have been found at a much lower frequency than females, which suggests that one male will spawn with several females (1). Populations of the blackspot tuskfish are not thought to vary greatly in density from one place or time to another; therefore it probably doesn’t form large spawning aggregations (1). In Japan, the blackfish tuskfish spawns from February to May (2).
The main threats to the blackspot tuskfish are over-fishing and habitat destruction. Recreational fishing, commercial fishing for the live fish and aquarium trades, and un-sustainable subsistence fishing practices, such as the use of poison or explosives, are contributing to the decline in blackspot tuskfish stocks throughout its range (1).
The blackspot tuskfish is of high economic importance in southeast Asia. Many of the blackspot tuskfish captured in this region are only 20 to 35 centimetres in length, and therefore are not likely to be sexually mature. Although overexploitation is suspected in southeast Asia, there is little data to verify the true extent (1).
Continued destruction of coral-reef ecosystems is likely to fragment blackspot tuskfish populations and result in its decline. An estimated 56 percent of coral reefs in southeast Asia are at high risk (1).
The threats faced by the blackfish tuskfish species are further exacerbated by its low reproductive rate (7).
In Australia, there are a selection of enforced laws which aim to minimise the negative impact that human activities are having on populations of the blackspot tuskfish and other species. These laws vary depending on the location and include a minimum legal length (MLL), with blackspot tuskfish only being retained if they measure over 30 or 40 centimetres. Catch limits of between four and eight fish per person per day are also in place. Other conservation efforts in Australian waters include the enforcement of no-take zones and localised spear-fishing bans (1).
In Asia, no official conservation actions are in place for this species, but in Okinawa, local fishermen are reported to have implemented a voluntary minimum weight restriction of one kilogram (1).
The coral triangle, which covers most of the blackspot tuskfish territory, is the subject of conservation efforts of many NGOs such as the WWF, Conservation International, and The Nature Conservancy. While many marine parks have been set up throughout this area, these are highly populated and the establishment of sustainable fishing practices has proven to be difficult to implement for a number of reasons. Logistical, socio-economic and cultural factors complicate the task of enforcing conservation actions in many areas and because of this, many of the coral triangles’ protected zones are recognised as such only on paper (1).
To find out more about the blackspot tuskfish:
Fishbase – blackspot tuskfish
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- Anal fin: in fish, an unpaired fin on the under surface of the fish, behind the anus.
- Crustaceans: diverse group of animals with jointed limbs and a hard external skeleton, characterised by the possession of two pairs of antennae, one pair of mandibles (mouthparts used for handling and processing food) and two pairs of maxillae (appendages used in eating, which are located behind the mandibles). Includes crabs, lobsters, shrimps, woodlice and barnacles.
- Dorsal fin: the unpaired fin found on the back of the body of fish, or the raised structure on the back of most cetaceans (whales, dolphins and porpoises).
- Invertebrates: animals with no backbone, such as insects, crustaceans, worms, molluscs, spiders, cnidarians (jellyfish, corals, sea anemones) and echinoderms.
- Pectoral fins: in fish, the pair of fins that are found on either side of the body just behind the gills. They are generally used for balancing and braking.
- Protogynous hermaphrodite: an animal that begins its life cycle as a female, but later changes sex to become a male. This change may be based on internal or external triggers.
- Spawning: the production or depositing of eggs in water.
IUCN Red List (November, 2011)
- Sadovy, Y. and Cornish, A.S. (2000) Reef Fishes of Hong Kong. Hong Kong University Press, Hong Kong.
- Randall, J.E., Allen, G.R. and Steene, R.C. (1996) Fishes of the Great Barrier Reef and Coral Sea. University of Hawaii Press, Hawaii.
- Beaufort, L.F. (1922) The Fishes of the Indo-Australian Archipelago. VIII. Percomorphi (continued). Cirrhitoidea, Labriformes, Pomacentriformes. E.J. Brill, Leiden.
Carpenter, K.E. and Niem, V.H. (2001) The Living Marine Resources of the Western Central Pacific. Volume 6: Bony Fishes Part 4 (Labridae to Latimeriidae), Estuarine Crocodiles, Sea Turtles, Sea Snakes and Marine Mammals. Food and Agriculture Organisation of the United Nations, Rome. Available at:
- Lieske, E. and Myers, R. (2001) Coral reef fishes: Indo-Pacific Caribbean. Harper Collins Publishers, London.
Fishbase - blackspot tuskfish (November, 2011)
- Kawabata, Y., Okuyama, J., Asami, K., Yoseda, K., and Arai, N. (2008) The post-release process of establishing stable home ranges and diel movement patterns of hatchery-reared black-spot tuskfish Choerodon schoenleinii. Journal of Fish Biology, 73: 1770-1782.