Greenland Shark

About the Greenland Shark

The Greenland Shark, also known as the Gurry Shark or the Large Sleeper Shark (due to its sluggish nature), is native to the Arctic and North Atlantic. The Greenlandic Inuit call them Eqalussuaq in their language, Kalaallisut, and they have a number of myths and legends about these fascinating creatures.

The Greenland Shark is one of the largest shark species alive and has the longest known lifespan of any vertebrate. It is estimated that these sharks can live for 300 years.

Biology and Lifespan

Most adults range between 2.4 m and 4.3 m (7.87–14.1 ft) in length but can reach up to 6 or 7 m (19.7–22.9 ft). Females are generally larger than males, reaching approximately 5.5 m (18 ft).They weigh an average of 900 kilos (1,984 lb).

Despite their monstrous size, they pose very little threat to humans as they inhabit freezing waters between -2 and 7 degrees Celsius (28.4–44.6 °F). Additionally, they are slow swimmers with a low-energy lifestyle and have the lowest tail-beat frequency relative to body size of any fish species. Their lack of speed is associated with their slow metabolism, slow growth rate, late sexual maturity and extreme longevity. Greenland sharks grow at an estimated rate of just 1 cm (0.4 in) per year.

The majority of these sharks are blind due to common parasites (Ommatokoita elongata) that attach themselves to their corneas. Fortunately, they do not need their sight to live in the dark depths of the ocean, where they predominantly rely on their sense of smell.

The flesh of the Greenland Shark is toxic due to a high concentration of trimethylamine N-oxide in its tissues. This is an evolutionary adaptation that aids buoyancy in deep waters. Inuit hunters treat and dry the meat in order to make it safe for human consumption and avoid feeding it raw to their sledge dogs, as it causes symptoms similar to drunkenness. In Iceland, fermented Greenland Shark meat is known as hákarl.

Reproduction

Reproduction is ovoviviparous, meaning embryos develop in eggs inside the mother’s body. Females give birth to between 2 and 10 pups measuring 40–100 cm (15.7–39.4 in) at birth. Males reach maturity at 2.84 m (9.3 ft) in length, while females mature at around 4.19 m (13.7 ft). It is estimated that Greenland Sharks reach sexual maturity at around 156 years of age, and generation length is thought to be between 150 and 200 years. Their gestation period, reproductive cycle and mating sites are still unknown.

Behaviour

Greenland Sharks are scavengers and opportunistic feeders. Although they are capable of short bursts of speed and have been known to ambush sleeping seals, they generally prefer to eat animals that are already dead. They are attracted to the smell of rotting meat and often subsist on drowned animals.

Their diet includes fish, seabirds, seals, small whales, crustaceans, molluscs and in one remarkable case, an entire reindeer was found in the stomach of a Greenland Shark. Fish appear to be their most important prey overall.

Conservation

Commercial hunting for their liver oil ceased in 1960, but they are still classified as vulnerable by the IUCN because they continue to be accidentally caught as bycatch. Greenland sharks’ extremely slow rate of reproduction make them particularly vulnerable to overfishing. Global bycatch has been estimated at approximately 3,500 sharks per year.

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Greenland Shark Gallery