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The Greenland shark – world’s oldest?

Very limited research has shown that the Greenland shark grows by about 0.5 to 1 cm per year. A shark that was captured and tagged off Greenland in 1936 was recaptured in 1952. In 16 years, the shark’s length had only increased by 6 centimetres. Assuming its growth rate is constant (no growth spurts), one can thus hypothesize that a mature seven-metre specimen could be over 200 years old, making the Greenland shark the longest-living vertebrate on the planet.

Greenland shark, picture by Doug Perrine

The Greenland shark was only first observed under water in 1995: the first underwater images of a live specimen were made in the Arctic in 1995, and the first video images of a shark swimming freely under natural circumstances were filmed by the GEERG team in 2003 in the St. Lawrence Estuary.

It is also a very slow shark, with an average speed of 0,3 m/sec. It is assumed its only predator is the sperm whale.

There are concerns that bycatch of Greenland sharks by the turbot fishing industry in Canada’s eastern Arctic territory of Nunavut, could affect the future of the species, of which little is known.

In certain countries, the Greenland shark is still hunted commercially for its oil. Between the latter half of the 19th century and 1960, fishermen in Greenland and Iceland caught up to 50,000 sharks annually. The oil contains Vitamin A and was used to light lamps, and there have even been proposals to use Greenland shark bycatch into biofuel…

The meat is toxic when fresh, inducing a drunk like state in both humans and dogs, but becomes edible once it has been dried. Unfortunately, the extent to which fishing is affecting the Greenland shark population is unknown, but there is speculation that its population could be declining, particularly given the shark’s slow growth rate.

Research is still very much needed, and there have been several tracking projects, a.o. by the Greenland Shark Elasmobranch Education and Research Group, which is tracking sharks from 2012 to 2017 in the St. Lawrence Estuary.

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A wealth of information about this elusive shark can be found at the excellent website of GEERG:
http://www.geerg.ca/gshark_1.html

The Arkive website also offers loads of good info:
http://www.arkive.org/greenland-shark/somniosus-microcephalus/image-G59814.html

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