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Biological Profiles




GREENLAND SHARK

Order: Squaliformes
Family: Dalatiidae
Genus: Somniosus
Species: microcephalus

Greenland Shark

Taxonomy

This shark has been classified as Somniosus microcephalus by Bloch and Schneider (1801). Roughly translated, Somniosus pertains to "sleep" which describes the shark's sluggish movement, and microcephalus literally means "small head." In the past, it has also been referred to as Squalus squatina (non Linnaeus, 1758), Squalus carcharis (Gunnerus, 1776), Squalus microcephalus (Bloch & Schneider, 1801), Somniosus brevipinna (Lesueur, 1818), Squalus borealis (Scoresby, 1820), Squalus norvegianus (Blainville, 1825), Scymnus gunneri (Thienemann, 1828), Scymnus glacialis (Faber, 1829), Scymnus micropterus (Valenciennes, 1832), Leiodon echinatum (Wood, 1846), and Somniosus antarcticus (Whitley, 1939).


Common Names

Somniosus microcephalus is commonly referred to as the Greenland shark and is also known as the sleeper shark, ground shark, gray shark, and gurry shark in English-speaking countries. Internationally, it is referred to as eishai (Germany), ekalugssuak (Greenland), ekaluggsup piara (Greenland), ekalukjuak (Quebec), eqaludjuaq (Quebec), eqalugssuak (Greenland), ekaluksuak (Greenland), eqalukuak (Canada), eqalussuak (Greenland), eqalusuak (Greenland), Groenlandse haai (Netherlands, South Africa, Turkey), gronlandhai (Germany), gronlandsaj (Denmark), grundhai (Germany), hakaring (Sweden), hakarl (Iceland), hakelling (Faeroe Island), hakjerring (Norway), havkal (Denmark), holkeri (Finland), iqalugjuak (Canada), iqalujjuak (Canada), iqalukuak (Canada), laimargue (Canada), laimargue du Groenland (France), oakettle (UK), rechin de Groelanda (Romania), rekin polarny (Poland), squalo di groenlandia lemargo (Italy), tiburon boreal (Spain), tollo boreal (spain), tubarao da Gronelandia (Portugal), tubarao de Gronelandia (Portugal), and tubarao-de-noite (Portugal).


Geographical Distribution

The Greenland shark is typically found in the Northern Atlantic and Arctic regions. It has been reported as far east as France and Portugal, as far west as the Gulf of St. Lawrence, and as far south as Cape Cod and North Carolina. There have even been a few sightings of the shark in the Southern Atlantic near Argentina and in Antarctic waters.

World distribution map for the Greenland shark


Habitat

The Greenland shark ranges in depths of 0-3,937 feet (0 to 1,200 m) and temperatures of 34-68°F (1 to 12°C). In the north, the shark migrates near shore in search of warmer waters. It is usually spotted near the surface during the winter and retreats to depths of 591-1,804 feet (180 to 550 m) during the summer. In southern waters the shark is found near continental shelves and slopes and is found at a depth of about 3,937 feet (1,200 m). In 1988, an unmanned submarine spotted a 20 feet (6 m) long male Greenland shark at a depth of 7,218 feet (2,200 m) at the wreck of the SS Central America, which sank off the coast of Savannah, Georgia in 1857. This is 3,281 feet (1,000 m) deeper than the maximum reported depth of the shark and 273 miles (440 km) south of its southernmost sighting in North Carolina.


Biology
Greenland shark illustration
source: Fishes of the Western North Atlantic (1948)

· Distinctive Features
The Greenland shark is characterized by its large, heavy-set body which gives it a sluggish appearance and movement. It has a short, rounded snout, thin lips, and very small eyes. The dorsal and pectoral fins are very small, and it lacks spines in its dorsal fins. The gill openings are very small in comparison to its size and are located low on the sides of the shark's head.


· Coloration
The Greenland shark varies between a black, brown, and grey color. Although the shark is usually uniform in color, it may often be marked with dark lines or white spots along its back and sides.


Greenland shark dentition: upper and lower teeth from right-hand side, at center of mouth, from midway along the jaws and from the corner of the mouth of a specmen about 11 feet in length
source: Fishes of the Western North Atlantic (1948)

· Dentition
The teeth of the Greenland shark are very different in comparison of the top and bottom sets. The upper teeth are very thin and pointy and lack serrations. They range in number from 48 to 52. The lower teeth are interlocking and are broad and square, containing short, smooth cusps that point outward. The lower teeth range in number from 50 to 52.


Greenland shark denticles - illustration
source: Fishes of the Western North Atlantic (1948)

· Denticles
The denticles of the Greenland shark are uniform in characteristics over the entire body of the shark. They are cone shaped and curved towards the rear of the shark. They are in longitudal columns and are closely spaced. They have high axial crests and low lateral crests, and the bases of the denticles have four sides.

Greenland shark denticles - photograph
© Doug Perrine


·Size, Age, and Growth
Greenland sharks average in size from 8-14 feet (244 to 427 cm) with females being the larger sex. This shark reaches a maximum length of about 21 feet (640 cm); although, it may grow to 24 feet (730 cm). Growth of the shark is very slow due to the cold temperatures of its climate.


Lumpfish are a common prey item of the Greenland shark
courtesy NOAA
lumpfish

· Food Habits
The Greenland shark's most common food consists of a large variety of ocean dwellers such as other small sharks, skates, eels, herring, capelin, char, various gadoids, redfish, sculpins, lumpfish, wolfish, and flounders. Marine mammals, such as seals and porpoises, are often taken by Greenland sharks despite it being characterized as a very sluggish creature. A few Greenland shark specimens have even been found to contain an entire reindeer and parts of a horse. The shark is also known to feed off carrion and is attracted to ill-smelling meat. They often congregate in large numbers around fishing operations.


· Reproduction
The Greenland shark is an ovoviviparous species. The female carries a large number of soft-shelled eggs eventually giving birth to full-term embryos. Some eggs have been reported to be as large as goose eggs. One 16 feet (5 m) specimen was reported to have contained ten 15 inches (38 cm) long full-term embryos in one of its uteri.


Predators
There are no known natural predators of the mature Greenland shark, which is most likely due to its massive size.


Parasites
A common parasite of the Greenland shark is Ommatokoita elongata. This copepod attaches itself to the eyes of the shark causing corneal lesions which lead to impaired vision and even partial blindness. However, this does not significantly affect the shark since it does not rely on keen vision. On most Greenland shark specimens, usually only one eye is affected by a single female copepod. Some believe that the copepod is bioluminescent, attracting prey for the shark. However, there is no scientific evidence that supports this theory.


Importance to Humans

Although the Greenland shark is poisonous if eaten fresh, it is edible when the meat has been dried. The flesh of the shark contains high concentrations of urea and trimethylamine oxide, which is said to be intoxicating, inducing an alcoholic affect. For this reason, natives of Greenland are known to call someone who is drunk "shark-sick." Also, dogs that have been poisoned by the shark's meat are often called "drunk." The dried meat is used widely in Northern regions for sled dog, and occasionally human, consumption. Eskimos use the dried skin of the shark as leather for making boots and the lower dental bands of the shark as knives primarily for cutting hair.


Danger to Humans

According to the International Shark Attack File (ISAF) there has only been one reported attack of the Greenland shark on a human. Around 1859 in Pond Inlet, Canada, it was reported that a Greenland shark was caught containing a human leg in its stomach. This story, however, was only a report and was never scientifically investigated or proven. The lack of recorded attacks may only be due to the shark's habitat, which is much to cold to be populated by common swimmers, therefore, significantly reducing the chance of an attack on a human.


Conservation

It is speculated that the Greenland shark population is low, with an estimated doubling time of more than 14 years. Nevertheless, the shark supports fisheries in Norwegian, Iceland, and Greenland waters where it is captured for its liver oil. It is currently listed as "Near Threatened" by the World Conservation Union (IUCN). The IUCN is a global union of states, governmental agencies, and non-governmental organizations in a partnership that assesses the conservation status of species.




Prepared by:

Dane Eagle