Somniosus microcephalus

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WHAT TO LOOK FOR
A gigantic, heavy-bodied sleeper shark with a short, round snout, heavy cylindrical body, and small precaudal fins. It has rough skin with denticles with strong hook-like erect cusps. Its dorsal fins are low and of equal size, with the first dorsal fin being slightly closer to the pectoral fins than to the pelvics. The distance between the dorsal fin bases is about equal to the snout to the first gill slits. It also has a long lower caudal lobe, short caudal peduncle, and lateral keels present on the base of its caudal fin.

COLOR
Medium grey or brown, sometimes with transverse dark bands, small, dark spots and blotches, and small light spots.

SIZE
When born, they are about 1.3 ft [40 cm] long. Most adults are 8 to 14 ft [244 to 427 cm] in length, and their maximum length is likely to be over 21 ft [640 cm], possibly up to 24 ft [730 cm].

HABITAT
These sharks prefer continental and insular shelves and upper slopes to at least 3937 ft [1200 m] deep. They also prefer water temperatures between 33 and 53.6ºF [0.6 and12ºC]. They tend to move inshore during the Arctic winter (from intertidal and surface in shallow bays and river mouths), and retreat to 591 to 1804 ft [180 to 550 m] when temperatures rise. In the north Atlantic, these sharks may move into shallower water in the spring and summer.

DISTRIBUTION
North Atlantic and Arctic oceans, occasionally extending to Portugal.

BIOLOGY
General – A highly conspicuous, possibly luminescent, copepod parasite often attached to the cornea of the sharks’ eye is speculated to lure prey species to the shark under a mutualistic and beneficial relationship.
Prey – Active fishes, invertebrates, seabirds, and seals. They also feed on dead cetaceans and drowned horses and reindeer.
Reproduction – Ovoviviparous, with 10 pups per litter.

BEHAVIOR
These sharks are sluggish and offer little resistance to capture. They are easily fished through iceholes, but they are able to capture large and active prey.

STATUS
They are abundant and traditionally fished by hook and line, longline, or gaff for their liver oil. They are also taken in nets and cod traps. Their meat is toxic when fresh (unless washed), but it is harmless when dried or semi-putrid. They are used for human and sled-dog food. Eskimos use their skin for boots, and sharks’ lower dental bands as knives. They are considered harmless to man, and there have been no confirmed incidents of these sharks biting people.