Grey Nurse Shark
From Biocrawler, the free encyclopedia.
| Grey Nurse Shark Conservation status: Vulnerable | ||||||||||||||
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| Carcharias taurus Rafinesque, 1810 |
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Distribution
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 behaviour, becoming more active during the night. 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. Through the 1950s and 1960s it was hunted to near extinction in Australian waters by spearfishing, and numbers there are only slowly making a resurgence. The Eastern Australian population is critically endangered, whereas in the west of the continent the population is listed as vulnerable.
Anatomy
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 3.2m (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").
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 intra-uterine cannibalism, is making it harder for the shark population to rebound from the near extinction. As a result, scientists are working on an plan to artificially inseminate and breed the sharks with test tubes, in order to increase their population.[1] (http://www.biocrawler.com/encyclopedia/Grey_Nurse_Shark#endnote_CNN)
See also
References
- ^ "'Scientists to breed test-tube sharks' (http://www.cnn.com/2005/TECH/science/07/28/test.tube.sharks.reut/index.html)", CNN, (July 28, 2005)
- Barry Bruce, John Stevens, Nick Otway: Site fidelity, residency times and activity space in grey nurse sharks in eastern Australia
- "Carcharias taurus (http://www.fishbase.org/Summary/SpeciesSummary.cfm?genusname=Carcharias&speciesname=taurus)". FishBase. Ed. Ranier Froese and Daniel Pauly. 09 2005 version. N.p.: FishBase, 2005.
- "Carcharias taurus" (TSN 159888) (http://www.itis.usda.gov/servlet/SingleRpt/SingleRpt?search_topic=TSN&search_value=159888). Integrated Taxonomic Information System. N.p.: Integrated Taxonomic Information System, 2006. Accessed on 23 January 2006.
External links
- Grey Nurse shark in Byron Bay (http://www.planula.com.au/dive/uwphoto2004/large/grey_nurse_shark.html) - one of the worlds known congregation areas for Grey Nurse sharks
- The Tangled Taxonomic History of the Sandtiger Shark (http://www.elasmo-research.org/education/topics/ng_sandtiger_taxonomy.htm)
