Gurry shark, Grey shark
The Greenland shark (Somniosus microcephalus), also known as the gurry shark or grey shark, is a large shark of the family Somniosidae ("sleeper sharks"), closely related to the Pacific and southern sleeper sharks. The Greenland shark is a potentially important yet poorly studied cold-water species inhabiting the North Atlantic and Arctic Oceans.
The Greenland shark has the longest known lifespan of all vertebrate species estimated to be between 250 and 500 years; it is among the largest extant species of shark. It reaches sexual maturity at about 150 years of age and pups are born alive after an estimated gestation period of 8–18 years.It is a generalist feeder, consuming a variety of available foods. As an adaptation to living at depth, it has 3 kinds of hemoglobin and a high concentration of trimethylamine N-oxide in its tissues to increase buoyancy. This causes the meat to be toxic to mammals. Greenland shark flesh, treated to reduce toxin levels, is eaten in Iceland as a delicacy known as kæstur hákarl. As it lives in the cold depths of the Arctic and North Atlantic, isolated from human activity, it is not known to be a threat to humans, and no attacks have been recorded.
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CarnivoreA carnivore meaning 'meat eater' is an organism that derives its energy and nutrient requirements from a diet consisting mainly or exclusively of a...
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PiscivoresA piscivore is a carnivorous animal that eats primarily fish. Piscivorous is equivalent to the Greek-derived word ichthyophagous. Fish were the die...
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OvoviviparousOvoviviparity, ovovivipary, ovivipary, or aplacental viviparity is a term used as a "bridging" form of reproduction between egg-laying oviparous an...
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PolygynandryPolygynandry is a mating system in which both males and females have multiple mating partners during a breeding season.
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SolitaryG
starts withThe Greenland shark is likely one of the largest living species of shark. It usually grows to between 2.4 and 7 m (7.9 and 23.0 ft) long and weighs between 400 and 1,400 kg (880 and 3,090 lb). The all-tackle International Game Fish Association (IGFA) record for this species is 775 kg (1,709 lb).
Males are typically smaller than females. 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 a thickset species, with a short, rounded snout, small eyes, and very small dorsal and pectoral fins. The gill openings are very small for the species' great size.
Coloration can range from pale creamy-gray to blackish-brown and the body is typically uniform in color, though whitish spots or faint dark streaks are occasionally seen on the back.
The shark is often infested by the copepod Ommatokoita elongata, a crustacean which attaches itself to the shark's eyes. It was speculated that the copepod may display bioluminescence and thus attract prey for the shark in a mutualistic relationship, but this hypothesis has not been verified. These parasites also damage the eyeball in several ways, leading to almost complete blindness. This does not seem to reduce the life expectancy or predatory ability of Greenland sharks, due to their strong reliance on smell and hearing.
The shark occupies what tends to be a very deep environment seeking its preferred cold water (−0.6 to 12 °C or 31 to 54 °F) habitat. As an ectotherm living in a just-above-freezing environment, the Greenland shark is sluggish and slow-moving, with the lowest swim speed and tail-beat frequency for its size across all fish species, which most likely correlates with its very slow metabolism and extreme longevity. It swims at 1.22 km/h (0.76 mph), with its fastest cruising speed only reaching 2.6 km/h (1.6 mph). Because this top speed is a fraction of that of a typical seal in their diet, biologists are uncertain how the sharks are able to prey on the seals. It is hypothesized that they may ambush them while they sleep.
Greenland sharks migrate annually based on depth and temperature rather than distance, although some do travel. During the winter, the sharks congregate in the shallows (up to 80° north) for warmth but migrate separately in summer to the deeps or even farther south. The species has been observed at a depth of 2,200 metres (7,200 ft) by a submersible investigating the wreck of the SS Central America that lies about 160 nautical miles (180 mi; 300 km) east of Cape Hatteras, North Carolina. Daily vertical migration between shallower and deeper waters has also been recorded.
In August 2013, researchers from Florida State University caught a Greenland shark in the Gulf of Mexico at a depth of 1,749 m (5,738 ft), where the water temperature was 4.1 °C (39.4 °F). Four previous records of Greenland shark were reported from Cuba and the northern Gulf of Mexico. A more typical depth range is 0–1,500 m (0–4,900 ft), with the species often occurring in relatively shallow waters in the far north and deeper in the southern part of its range.
In April 2022, a large Somniosus shark was caught and subsequently released on Glover's Reef off the coast of Belize. This shark was identified as being either a Greenland shark or a Greenland/Pacific sleeper shark hybrid. This observation is notable for being the first possible record of a Greenland shark from the Western Caribbean, and being caught on a nearshore coral reef (the only other record of this species from the Caribbean was made from a deep-water habitat off the Caribbean coast of Colombia). The discovery indicates that Greenland sharks may have a wider distribution in the tropics, primarily at greater depths, than previously believed.
The Greenland shark has the longest known lifespan of all vertebrate species. One Greenland shark was tagged off the coast of Greenland in 1936 and recaptured in 1952. Its measurements suggest that Greenland sharks grow at a rate of.mw-parser-output.frac{white-space:nowrap}.mw-parser-output.frac.num,.mw-parser-output.frac.den{font-size:80%;line-height:0;vertical-align:super}.mw-parser-output.frac.den{vertical-align:sub}.mw-parser-output.sr-only{border:0;clip:rect(0,0,0,0);clip-path:polygon(0px 0px,0px 0px,0px 0px);height:1px;margin:-1px;overflow:hidden;padding:0;position:absolute;width:1px}0.5–1 cm (1⁄4–1⁄2 in) per year. In 2016, a study based on 28 specimens that ranged from 81 to 502 cm (2 ft 8 in – 16 ft 6 in) in length used radiocarbon dating of crystals within the lenses of their eyes to determine their approximate ages. The oldest of the animals sampled, which was also the largest, had lived for 392 ± 120 years, and was consequently born between 1504 and 1744. The authors further concluded that the species reaches sexual maturity at about 150 years of age. Efforts to conserve Greenland sharks are particularly important due to their extreme longevity, long maturation periods, and the heightened sensitivity of large shark populations.
The Greenland shark is an apex predator and eats primarily fish, although they have been observed actively hunting seals in Canada. The prey found in the stomachs of Greenland sharks is an indicator of the active hunting patterns of these predators. Recorded fish prey have included smaller sharks, skates, eels, herring, capelin, Arctic char, cod, rosefish, sculpins, lumpfish, wolffish, and flounder. Small Greenland sharks eat predominantly squid, while the larger sharks that are greater than 200 cm (79 in) were discovered eating prey such as epibenthic and benthic fishes as well as seals. The largest of these sharks were found having eaten redfish, as well as other higher trophic level prey.
It is proposed, that because of their slow speeds and low twitch speed muscle fiber, Greenland sharks hunt marine mammals such as seals and smaller cetaceans that are asleep, injured, or sick. Regarding most other benthic species, they utilize their cryptic coloration, and approach prey undetected before closing the remaining distance, expanding their buccal cavity to create suction, drawing in prey. This is the likely explanation for why the gut contents of Greenland sharks are often whole prey specimens.
Greenland sharks have also been found with remains of moose and reindeer (in one case an entire reindeer body) in their stomachs. The Greenland shark is known to be a scavenger and is attracted by the smell of rotting meat in the water. The sharks have frequently been observed gathering around fishing boats. They also scavenge on seals.
Although such a large shark could easily consume a human swimmer, the frigid waters it typically inhabits make the likelihood of attacks on people very low. No cases of predation on humans have been verified.
As recently as 1957, females were found not to deposit eggs in the bottom mud, but retain the developing embryos within their bodies so they are born alive (a process known as ovoviviparity) after an estimated gestation period of 8–18 years. About ten pups per litter is normal, each initially measuring some 38–42 cm (15–16+1⁄2 in) in length. Within a Greenland shark's uterus, villi serve a key function in supplying oxygen to embryos. It is speculated that due to embryonic metabolism dealing with reproduction, this only allows for a limited litter size of around 10 pups. It has been estimated that due to their extreme longevity, Greenland sharks can have 200 to 700 pups during their lifetime.
The shark has historically been hunted for its liver oil up until the development of synthetic oils and cessation of export of liver oil and skin from Greenland in the 1960s. In the 1970s, the species was perceived as a problem for other fisheries in western Norway and the government subsidized a fishery to reduce the stock of the species.
Approximately 3,500 individuals are taken each year in the Northwest Atlantic. Of this number, 89% comes from the Barents Sea, Iceland, Greenland, and the Canadian Arctic.
The shark is likely affected by quantity, dynamics, and distribution of Arctic sea ice. The rate of projected loss of sea ice will continue to negatively influence the abundance, distribution and availability of prey, while, at the same time, providing greater access for fishing fleets. There is greater potential for new fisheries to develop as more productive and abundant southerly species invade the warming Arctic waters.
As both scavengers and active predators, Greenland sharks have established themselves as apex predators in Arctic ecosystems. They eat a wide variety of fish, seals, and other prey within these ecosystems and have an important role in the intricate food web.
Greenland sharks are recognized as the longest-lived vertebrates on earth. They have a slow growth rate, late maturity period, and low fecundity, making the management and conservation of this species very important. As a result of their low productivity and extreme longevity, this species is particularly susceptible to overfishing. Therefore, Greenland sharks' longevity and conservative life history traits, in tandem with their vulnerability to accidental catching and commercial fishing, promotes a growing concern for the sustainability of this species.
