Grey nurse shark
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| Carcharias taurus Rafinesque, 1810 |
The grey nurse, spotted ragged-tooth or sand tiger, Carcharias taurus, is a large shark inhabiting coastal waters worldwide, with many different names in different countries in the world. Despite a fearsome appearance and strong swimming abilities, it is a relatively placid and slow moving animal. It is considered not aggressive unless provoked[1].
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[edit] Habitat and Distribution
Research indicates that generally the shark remains within a kilometre of its aggregation site, and stays close to the ocean floor. Present throughout the world, in the Atlantic, Indian and Pacific Oceans, the shark is a common sight in many areas of the world.
[edit] Anatomy and appearance
Their bodies are stout, with two large dorsal fins and the tail is elongated and have a long upper lobe. The shark has a precaudal pit but no caudal keels. It grows to a length of 3.2 m (about 10' 6"). Male grey nurse sharks mature at 2.1 m (about 6' 11"); and females mature at 2.2 m (about 7' 3").
[edit] Diet
The diet of Carcharias taurus consists of bony fishes including jewfish and kingfish, other sharks and rays, squid, crabs and lobsters [2].
[edit] Behaviour
The sharks typically congregate in coastal waters, at depths of 10-60 metres, although deeper depths have been recorded. Often they will shelter in caves or gutters during the day, and come out at night to feed. During the day they exhibit sluggish behavior, becoming more active during the night. The grey nurse shark is the only known shark to gulp and store air in its stomach in order to maintain neutral buoyancy while swimming.
[edit] Reproduction
The species is ovoviviparous, i.e. bearing live young from eggs which hatch inside the uterus. Female sharks have two uteruses. Inside the uterus the young sharks develop and eat each other, so typically only two young sharks are born for each gestation period, which lasts 6-9 months. This process, also known as intrauterine cannibalism, is making it harder for the shark population to rebound from the near extinction. As a result, scientists plan to artificially inseminate and breed the sharks, in order to increase their population.[3] Another plan is to remove the shark embryos from the uterus before cannibalism can take place and then artificially gestate them.[4]
[edit] Importance to humans
Through the 1950s and 1960s it was hunted to near extinction in Australian waters, and numbers there are making a resurgence. The Eastern Australian population whilst listed as critically endangered is thought to be in excess of 2000, whereas in the west of the continent the population is listed as vulnerable.
[edit] See also
- Wolf Rock, Queensland, an important habitat area
- List of sharks
- Threatened fauna of Australia
[edit] Foot notes
- ^ Sandtiger Shark profile at the Florida Museum of National History.
- ^ Recovery Plan for the Grey Nurse Shark in Australia
- ^ Scientists to breed test-tube sharks, CNN.
- ^ Sibling sharks turn predator in the grey nursery, Sydney Morning Herald.
[edit] References
- Pollard & Smith (2000). Carcharias taurus. 2006 IUCN Red List of Threatened Species. IUCN 2006. Retrieved on 09 May 2006. Database entry includes justification for why this species is vulnerable
- Barry Bruce, John Stevens, Nick Otway: Site fidelity, residency times and activity space in grey nurse sharks in eastern Australia
- "Carcharias taurus". FishBase. Ed. Ranier Froese and Daniel Pauly. 09 2005 version. N.p.: FishBase, 2005.
- Carcharias taurus (TSN 159888). Integrated Taxonomic Information System. Accessed on 23 January 2006.
- Grey Nurse Shark, Carcharias taurus MarineBio"
[edit] External links
- Grey nurse shark in Byron Bay - one of the worlds known congregation areas for Grey Nurse sharks
- The tangled taxonomic history of the sand tiger shark
- Sand tiger shark entry at the Florida Museum of Natural History
- School of sharks and a diver
[edit] Gallery
 Grey nurse shark at the Minnesota Zoo |
 Grey nurse shark at the Minnesota Zoo |
