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The Harp Seal or Saddleback seal is a species of earless seal native to the northernmost Atlantic Ocean and adjacent parts of the Arctic Ocean. Officially Pagophilus groenlandicus, which means ice-lover from Greenland, it has a synonym Phoca groenlandica or Greenland seal.
The Harp seal has a black face with silvery-gray body. It has black harp or wishbone shaped markings on the back. They exhibit little sexual dimorphism.
The pup has a white coat at birth. Dentition is I 3/2, C 1/1, PC 5/5=34.
Harp seals combine anatomical and behavioral approaches to managing their body temperatures, instead of elevating their metabolic rate and energy requirements.
A thick coat of blubber insulates its body and provides energy when food is scarce or during fasting. Blubber also streamlines its body for more efficient swimming. Brown fat warms blood as it returns from the body surface as well as providing energy, most importantly for just-weaned pups.
Flippers act as heat exchangers, warming or cooling the blood as needed. On ice, the seal can press its foreflippers to its body and its hindflippers together to reduce heat loss.
Vision is its critical sense. Its eye is proportionally large and contains a large spherical lens, improving its focusing ability. Its pupil is mobile to help it adapt to the intense glare of the Arctic ice. Its retina is rod-dominated and backed by a cat-like and reflective tapetum lucidum, enhancing its low light sensitivity. Its rods best sense blue-green, while its cones help with bright light and may provide some color discrimination. Its cornea is constantly tear-covered, to protect it from salt. Lacking tear ducts, it "cries" to remove its tears.
It can hear and determine direction above and below the water surface. Its range in air is similar to humans', but is less sensitive. As an earless seal, it lacks a pinna. Its underwater range extends to 60 kHz. It hears better underwater than on the surface, except that water limits its frequency range.
On ice, the mother identifies her offspring by smell. This sense may also warn of an approaching predator. Underwater, this seal closes its nostrils and smells nothing.
On the ice, pups call their mothers by "bawling" and "mumble" while playing with others. Adults "growl" and "warble" to warn off others.
Underwater, adults express themselves with 19+ call types during courting and mating.
Females mature sexually at age 5–6. Annually thereafter they bear one pup, usually in late February. The fertilized egg grows into a spherical embryo that implants in the uterus only after 3 or so months, to allow birth to take place while sufficient pack ice is available.
Newborn pups weight around 11 kilograms (24 lb) and are 80–85 centimetres (31–33 in) long. After birth, the mother only feeds that pup. During the 12 day nursing period, the mother does not eat, losing up to 3 kilograms (7 lb) per day. Harp Seal milk contains up to 48% fat, so pups gain over 2.2 kilograms (5 lb) per day. During this time the juvenile's "greycoat" grows in beneath the white neonatal coat, and it weighs 80 pounds (36 kg). Weaning is abrupt; the mother turns from nursing to promiscuous mating, leaving the pup behind on the ice. While courtship starts on the ice, mating usually takes place in the water.
The stranded pup cries at first, and then becomes sedentary to conserve body fat. Within a few days, it sheds its white coat, reaching the "beater" stage.
Pups are unable to swim or find food until 7–8 weeks old or until the ice melts, leaving them vulnerable to polar bears and other predators. This fast costs them up to 50% of their weight. As many as 30% of pups die during their first year, due in part to their early immobility because they learn to swim only slowly.
At about 13–14 months, the pup molts again, becoming a "bedlamer". Juveniles molt several times, producing a "spotted harp", before the adult's harp-marked pelt fully emerges after several years (or not all in females).
Seals congregate annually on the ice to molt before migrating to summer feeding grounds. Their lifespan extends some 30 years.
Migration and vagrancy
Harp Seals are strongly migratory. The northwest population regularly moves up to 4,000 kilometers (2,485 mi) northeast outside of the breeding season; one individual was located off the north Norwegian coast, 4,640 kilometers (2,883 mi) east-north-east of its tagging location. Their navigational accuracy is high, with good eyesight an important factor. They are occasionally found as a vagrant, south of their normal range. In Great Britain, a total of 31 vagrants were recorded between 1800 and 1988,
More recently they reached Lindisfarne in Northumberland in September 1995, and the Shetland Islands in 1987. The latter was linked to a mass movement of Harp Seals into Norwegian waters; by mid-February 1987, 24,000 were reported drowned in fishing nets and perhaps 300,000 (about 10% of the world population) had invaded fjords as far south as Oslo. The animals were emaciated, likely due to humans competing for their prey.
Relation to humans
In Canada, commercial hunting season is from November 15 to May 15. Most sealing occurs in late March in The Gulf of St. Lawrence, and during the first or second week of April off Newfoundland, in an area known as "The Front". This peak spring period is generally what is referred to as the "Canadian Seal Hunt". Hunting Canadian whitecoats has been banned since 1987. In 2006, the St. Lawrence hunt officially started on March 25 due to thin ice caused by the year's milder temperatures. Inuit people living in the region hunt mainly for food and to a lesser extent, commerce.
In 2003, the three-year quota granted by the Department of Fisheries and Oceans was increased to 975,000, with a maximum of 350,000 in any two consecutive years. In 2006, 325,000 Harp Seals, as well as 10,000 Hooded Seals and 10,400 Grey Seals were killed. An additional 10,000 animals are allocated to First Nations hunters. From 2004-2007, over 1 million were taken, 95% under the age of 3 months. Canada's Total Allowable Catch (TAC) for 2007, was 270,000, which was higher than the sustainable yield of 165,000.
The Canadian seal hunt is monitored by the Canadian Government. Although approximately 70% of the hunt occurs on "The Front", most private monitors focus on the St. Lawrence hunt, due to its more convenient location. 70-90,000 animals are taken from this population off the coast of Greenland.
The 2004 West Ice TAC was 15,00 "1+" animals (2 pups = 1+) almost double the sustainable catch of 8,200. Actual catches were 9,895 in 2004 and 5,808 in 2005.
The 2004 White Sea TAC was 45,000 1+ (2.5 pups = 1+). The catch was 22,474.
Notes and references
- ^ Kovacs, K. (2008). Pagophilus groenlandicus. In: IUCN 2008. IUCN Red List of Threatened Species. Downloaded on 29 January 2009.
- ^ a b c d e f g h i j k l m n o p q r s t u v Lavigne, David M. (2009). Perrin, William F.; Wursig, Bernd; Thewissen, J. G. M.. eds. Encyclopedia of Marine Mammals (2 ed.). 30 Corporate Drive, Burlington Ma. 01803: Academic Press. ISBN 978-0-12-3733553-9. http://www.elsevier.com/wps/find/bookdescription.cws_home/716899/description#description.
- ^ a b Ronald, K., & Healey, P. J. (1981). Harp Seal. Chapter 3 in Ridgeway, S. H., & Harrison, R. J., eds. Handbook of Marine Mammals, vol. 2 Seals. Academic Press, London.
- ^ Sergeant, D. E. (1973). Transatlantic migration of a Harp Seal, Pagophilus groenlandicus. J. Fish. Res. Board Canada 30: 124-125.
- ^ King, J. E. (1993). Seals of the World, 2nd. ed. British Museum, London.
- ^ Corbet, G. B., & Harris, S., eds. (1991). The Handbook of British Mammals, 3rd. ed. Blackwell, Oxford.
- ^ Frankis, M. P., Davey, P. R., & Anderson, G. Q. A. (1997). Harp Seal: a new mammal for the Northumberland fauna. Trans. Nat. Hist. Soc. Northumbria 57 (4) 239-241.
- ^ Anon (1987). Harp Seals, Brunnich's Guillemots and White-billed Divers Twitching 1 (3): 58.
The Northwest population:
- Hammill, M.O. and Stenson, G.B., (2000). Estimated Prey Consumption by Harp seals (Phoca groenlandica), Hooded seals (Cystophora cristata), Grey seals (Halichoerus grypus) and Harbour seals (Phoca vitulina) in Atlantic Canada. J. Northw. Atl. Fish. Sci., Vol. 26:1-23
- Lawson, J.W., Anderson, J.T., Dalley, E.L. and Stenson, G.B. (1998). Selective foraging by harp seals Phoca groenlandica in nearshore and offshore waters of Newfoundland, 1993 and 1994. Marine Ecology Progress Series Vol. 163:1-10.
- Shelton, P.A. and Healey, B.P. (1999). Should depensation be dismissed as a possible explanation for the lack of recovery of the northern cod (Gadus morhua) stock? Can. J. Fish. Aquat. Sci. 56:1521-1524
- Stenson, G.B., Hammill, M.O. and Lawson, J.W.(1997). Predation by Harp Seals in Atlantic Canada: Preliminary Consumption Estimates for Arctic Cod, Capelin and Atlantic Cod. J. Northw. Atl. Fish. Sci., Vol. 22:137-154
The White Sea and West Ice populations:
- Hamre, J.(1994). Biodiversity and exploitation of the main fish stocks in the Norwegian- Barents Sea ecosystem. Biodiversity and Conservation 3:473-492
- Haug, T., Kroeyer, A.B., Nilssen, K.T., Ugland, K.I. and Aspholm, P.E., (1991). Harp seal (Phoca groenlandica ) invasions in Norwegian coastal waters: Age composition and feeding habits. ICES journal of marine science. Vol. 48, no. 3:363-371
- ICES 2001. Report of the Joint ICES/NAFO Working Group on Harp and Hooded Seals, ICES Headquarters, 2–6 October 2000. ICES CM, 2001, ACFM:8, 40 pp.
- Nilssen, K.T., Pedersen, O.-P., Folkow, L.P., & Haug. T. 2000. Food consumption estimates of Barents Sea harp seals. NAMMCO Sci. Publ. 2:9-28.