Gurry shark, grey shark, Somniosus microcephalus
The head is elongated and the distance from the tip of the snout to the pectoral fins was 23% of the total length in a 2.99m long shark. The snout is short and rounded. The massive body is cylindrical. There are no spines at the base of either dorsal fin. The dorsal fins are small and of equal size. The base of the first dorsal fin is closer to the pelvic fins than to the pectoral fins. The distance between the dorsal fins exceeds the distance between the tip of the snout and the second gill slit. Lateral keels on the caudal peduncle are absent. Caudal peduncle short. The distance between the bases of the second dorsal and caudal fins is less than twice the length of the base of the second dorsal fin. The gill slits are very small for a shark of this size. Colouration ranges from pale grey-cream to black-brown. It is usually uniform, but there may be white patches or dark stripes on the back. The upper and lower teeth are very different: the lower teeth are broad, with a large flattened root and the tips sharply angled towards the corners of the mouth; the upper teeth are narrow and symmetrical.
Greenland sharks are one of the slowest sharks. Their average speed is 1.6 km/h and their maximum speed is 2.7 km/h, which is half the maximum speed of seals. This begs the question of how these lumbering fish are able to hunt such fast prey. There is evidence that Greenland sharks stalk sleeping seals.
They are the most northerly and cold-loving of all sharks. They are widely distributed throughout the North Atlantic - off the coasts of Greenland, Iceland, Canada (Labrador, New Brunswick, Nunavut, Prince Edward Island), Denmark, Germany, Norway, Russia and the USA (Maine, Massachusetts, North Carolina).
They are found on the continental and island shelves and on the upper part of the continental slope from the water surface to a depth of 2200 m. In winter in the Arctic and North Atlantic they are found in the surf zone in shallow bays and estuaries. In winter in the Arctic and North Atlantic they are found in the surf zone, in shallow bays and estuaries near the surface. In summer, they stay at depths of 180 to 550 m. In lower latitudes (Gulf of Maine and North Sea), these sharks are found on the continental shelf and migrate to shallow waters in spring and autumn. Temperatures in their habitats range from 0.6 to 12°C. Sharks tagged under the ice off Baffin Land in late spring preferred to stay in deep water in the morning and move to shallow water for the night at midday.
The maximum recorded length is 6.4 m and the mass is about 1 tonne. The largest individuals can reach 7.3 metres and weigh up to 1.5 tonnes. However, the average length of these sharks is between 2.44 and 4.8 m and the mass does not exceed 400 kg.
Life history and Behavior
The scientists' analysis showed that the average lifespan of these sharks is at least 272 years, making them long-lived record breakers among vertebrates. The researchers estimated the age of the largest shark (502 centimetres long) to be 392 ± 120 years, and individuals less than 300 centimetres long were less than a hundred years old.
Food and feeding habits
They are super predators. Their diet is based on fish such as small sharks, rays, eels, herring, capelin, char, cod, sea bass, sottidae, anarhichadidae, cyclopterus and flounder. They may also hunt seals. If necessary, they will eat carrion: cases have been reported of polar sharks finding the remains of polar bears and reindeer in their stomachs. They are known to be attracted to the smell of rotting meat in the water. They often congregate in large numbers around fishing vessels.
Oviparous. The breeding season is in summer. The female carries about 500 soft, ellipsoidal eggs. The eggs are about 8 cm long and lack a horny capsule. There are about 10 newborns in a litter, which are 90 cm long.
Attacks on humans attributed to these sharks are extremely rare. They live in cold waters where it is virtually impossible to encounter humans. However, one case has been recorded of a shark following a ship in the Gulf of St Lawrence. Another shark chased a group of divers and forced them to the surface. Some fishermen believe they damage fishing gear and kill fish, and regard them as pests. Once caught, Greenland sharks put up little resistance.
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Tags: greenland shark