Porbeagle
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| Porbeagle | ||||||||||||||||
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| Lamna nasus Bonnaterre, 1788 |
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 Range of porbeagle (in blue)
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The porbeagle, Lamna nasus, is a pelagic predatory shark of the family Lamnidae. The porbeagle is considered vulnerable to extinction (critically endangered in the Northeast Atlantic), and the European Union has proposed listing the porbeagle under the United Nations Convention on International Trade in Endangered Species (CITES)[1].
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[edit] Naming
The origins of the name porbeagle are unknown. One suggestion is a combination of "porpoise" and "beagle", for it is fairly porpoise-like. The Oxford English Dictionary attributes its first appearance to a Cornish dialect. It is possible it is derived from two old French words meaning hog and nose.[2] The Greek lamna means shark and nasus means nose.
[edit] Distribution
The porbeagle's distribution ranges from the northeastern coast of North America, from New Jersey to Greenland and from the northwestern coast of Africa, Morocco or Western Sahara and the Mediterranean, and up to the waters off Iceland to the north coast of Norway and the northwestern coast of Russia. In the southern hemisphere its distribution is circumglobal from 30° to 60° south.
The porbeagle is listed as "Vulnerable" on the IUCN (World Conservation Union) Red List of Threatened Species. Canada also lists the porbeagle as an endangered species [3] overfishing has recently decimated numbers in British waters.
[edit] Habitat
The porbeagle is mainly a pelagic shark, but can be found in coastal waters. It lives in cold water commonly from about 5°C to 10°C (41°F to 50°F), but have been found down to 1°C (33°F) and up to 23°C (71°F). It can be found at the surface and to a depth of more than 700 metres.
[edit] Anatomy and appearance
The most distinguishing characteristic of the porbeagle is a white patch on the trailing edge of the dorsal fin. This distinguishes it from all other sharks in its family. It has two keels on the caudal fin, in common with the salmon shark.
The porbeagle is a stout and heavy shark, dark blue-grey on top and white underneath, with a conical snout. The porbeagle's maximum recorded size is 3.7 m (12 ft), and large specimens can weigh 160 to 250 kg (350 to 550 lb). Females in the northern hemisphere mature at around 7.6 to 8.5 feet (232-259 cm) in total length, and females in the southern hemisphere at around 6.1 to 6.6 feet (185-202 cm). Males in the northern hemisphere mature at around 5.4 to 6.8 feet (165-207 cm).[4] The average weight of this species is 135 kg (297 lb).[5]
[edit] Behaviour
The porbeagle is among the fastest sharks. It can jump fully out of the water, a behavior observed in only a few sharks. Porbeagles are unique in that they have been known to play tag with other porbeagles, pass around seaweed to other porbeagles, and toss driftwood out of the water in a manner similar to dolphins.[6]
[edit] Diet
The porbeagle is an opportunistic feeder, it eats mostly bony fish like mackerel, herring, lancetfish and sauries.
[edit] Reproduction
The porbeagle is ovoviviparous. Gestation period is about 8 to 9 months. Litters of up to 6 pups have been recorded but the normal size is about 4. Pups are about 60 to 80 cm long when born. Female porbeagles reach sexual maturity at about 12 to 13 years and males at 7 to 8 years.
[edit] References
- Stevens et al. (2005). Lamna nasus. 2006 IUCN Red List of Threatened Species. IUCN 2006. Retrieved on 11 May 2006. Database entry includes a range map and justification for why this species is vulnerable
- Lamna nasus (TSN 159911). Integrated Taxonomic Information System. Retrieved on 23 January 2006.
- "Lamna nasus". FishBase. Ed. Ranier Froese and Daniel Pauly. 09 2005 version. N.p.: FishBase, 2005.
[edit] Footnotes
- ^ IUCN (2007-02-22). More oceanic sharks added to the IUCN Red List. Press release. http://www.iucn.org/en/news/archive/2007/02/22_pr_sharks.htm. Retrieved on 2007-02-25.
- ^ Thrussell, Mike (1990). First Run Shark. Ward Lock. ISBN 0-7063-6930-0.
- ^ "Environment Canada: Species at risk". http://www.speciesatrisk.gc.ca/search/speciesDetails_e.cfm?SpeciesID=810. Retrieved on 2008-02-01.
- ^ http://www.flmnh.ufl.edu/fish/Gallery/Descript/Porbeagle/Porbeagle.html
- ^ http://www.shark.ch/Database/Search/species.html?sh_id=1029
- ^ ""Biology of the Porbeagle"". Reefquest Center for Shark Research. http://www.elasmo-research.org/education/shark_profiles/l_nasus.htm. Retrieved on 2009-04-21.
[edit] External links
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Wikimedia Commons has media related to: Lamna nasus |
