The Greenland shark, Somniosus microcephalus, also known as the sleeper shark, gurry shark, ground shark, grey shark, or by the Inuit languages name Eqalussuaq, is a large shark native to the waters of the North Atlantic Ocean around Greenland and Iceland. These sharks live farther north than any other shark species. They are closely related to the Pacific sleeper shark. This is one of the largest species of shark, of dimensions comparable to those of the great white shark. Large Greenland sharks grow to 6.4 m (21 ft) and 1000 kg (2200 lbs), and possibly up to 7.3 m (24 ft). It rivals the Pacific sleeper shark (possibly up to 7 m or 23 ft long) as the largest species in the family Somniosidae. The Greenland shark is known to be long-lived, with an estimated maximum life span of over 200 years.
The Greenland shark mostly eats fish, though it may also prey on marine mammals such as seals. Bite marks on dead seals at Sable Island, Nova Scotia and Hawarden suggest that this shark may be a major predator for them in the winter months. Greenland sharks have also been found with remains of polar bear and reindeer in their stomachs. The shark is colonized by the parasitic copepod Ommatokoita elongata that eats the shark's corneal tissue, but also helps to attract prey through bioluminescence.
Greenland sharks as food
The flesh of a Greenland shark is poisonous. This is due to the presence of the toxin trimethylamine oxide, which, upon digestion, breaks down into trimethylamine, producing effects similar to extreme drunkenness. Occasionally, sled dogs that end up eating the flesh are unable to stand up due to the neurotoxins. Similar toxic effects occur with the related Pacific sleeper shark, but not in most other shark species, whose meat is often consumed fresh. This was used as the basis of an attempted murder of the British Prime Minister in the fictional story: The Jimmy Coates Series.
However, it can be eaten if it is boiled in several changes of water or dried or fermented for some months to produce Kæstur Hákarl, often Hákarl for short. Traditionally this was done by burying the shark in boreal ground, exposing it to several cycles of freezing and thawing. It is considered a delicacy in Iceland and Greenland.
The Greenland shark's poisonous flesh has a high urea content, which gave rise to the Inuit legend of Skalugsuak, the first Greenland shark. The legend says that an old woman washed her hair in urine and dried it with a cloth. The cloth blew into the ocean to become Skalugsuak.
The Greenland Shark and Elasmobranch Education and Research Group (GEERG) has been studying the Greenland shark in the Saguenay Fjord and St. Lawrence Estuary since 2001. The Greenland shark has repeatedly been documented (captured or washed ashore) in the Saguenay since at least 1888. Accidental captures and strandings have also been recorded in the St. Lawrence Estuary for over a century.
Current research conducted by GEERG involves the study of the behaviour of the Greenland shark by observing it underwater using scuba and video equipment and by placing acoustic and satellite tags (telemetry) on live specimens; however, overall very little is known about this mysterious species.
There is now an argument suggesting that the Greenland is responsible for 'Seal Ripping' attacks on grey seals. These attacks cause a corkscrew pattern of cuts and tears which spiral around a seal's body, following the grain of the collagen within the muscles and running at 45 degrees to the seal's body. Seal deaths have been occurring over larger territories, including the north and east coasts of the UK, which suggests that the Greenland may be moving beyond its traditional habitat range.
- ^ O'Donnell, Jacinth. Jurassic Shark documentary (2000); broadcast on Discovery Channel, August 5, 2006
- ^ ADW: Somniosus microcephalus: Information. Animaldiversity.ummz.umich.edu. Retrieved on 2010-09-06.
- ^ Florida Museum of Natural History Ichthyology Department: Greenland Shark. Flmnh.ufl.edu. Retrieved on 2010-09-06.
- ^ Shark Predation on Sable Island Seals (July 2008)
- ^ "Greenland Shark" by discovery.com
- ^ . Retrieved 20 March 2008.
- ^ Skipper Uses Knife To Kill 600-Kilo Shark
- ^ O’Reilly, Lindsay. "The Greenland Shark", Canadian Geographic, March/April 2004. . Retrieved 1 July 2007.
- ^ a b Greenland Shark and Elasmobranch Education and Research Group
- ^ Idrobo Masters Thesis, February 2009.
- ^ "GEERG: The Greenland Shark" http://www.geerg.ca/gshark1.htm . Retrieved 5 July 2008.
- ^ Channel 5 documentary Retrieved 29 September 2010
|This article includes a list of references, but its sources remain unclear because it has insufficient inline citations.|
Please help to improve this article by introducing more precise citations where appropriate. (June 2008)
- Kyne et al. (2005). Somniosus microcephalus. 2006. IUCN Red List of Threatened Species. IUCN 2006. www.iucnredlist.org. Retrieved on 11 May 2006. Database entry includes justification for why this species is near threatened
- "Somniosus microcephalus". Integrated Taxonomic Information System. http://www.itis.gov/servlet/SingleRpt/SingleRpt?search_topic=TSN&search_value=160611. Retrieved 23 January 2006.
- Froese, Rainer, and Daniel Pauly, eds. (2006). "Somniosus microcephalus" in FishBase. May 2006 version.
- "Greenland Shark" on "As It Happens" May 6, 2008; CBC Radio 1(WMV file)