The Greenland Shark

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.

Lifestyle

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.[4] 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.

Reproduction

As recently as 1957 it was found that the females do not deposit eggs in the bottom ooze, but retain the developing embryos within their bodies so that they are born alive after an undetermined gestation period. 10 pups per litter is the norm, each measuring some 90 centimetres in length.
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.

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.

Research

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. However, recent research into the UK "corkscrew" seal deaths by the Sea Mammal Research Unit concluded that the UK seal deaths were unlikely to have been caused by predation from the Greenland shark, rather being caused by blunt mechanical trauma "consistent with the seals being drawn through a ducted propeller" that are found on many ships.

Dentition

When feeding on large carcasses, the shark employs a rolling motion of its jaw. The teeth of the upper jaw act as anchor while the lower jaw does the cutting. Teeth in the two halves of the lower jaw are strongly pitched in opposite directions.