Harp Seals separate into three populations according to their breeding locations; the White Sea, the West Ice between Jan Mayen and Greenland, and the Northwest Atlantic near Newfoundland and Labrador, Canada. Seals breeding in the Northwest Atlantic represent the largest population and are genetically different from seals breeding in the two other areas, which have not been proven genetically different from each other. They are however visually indistinguishable, and a degree of mixing between the populations occurs.
The Northwest population
There are no reliable estimates of the size of Northwest Atlantic population when commercial hunting began in the early 1800s. Several simulation models estimated virginal populations to be in the 3 to 4 million range. It is considered that the population recovered to about 3 million at the end of World War II, but subsequently declined by 50–66% between 1950 and 1970 due to commercial hunting in Canada. Quotas and other conservation measures since then have enabled the population to nearly triple in size to an unhealthily large 5.4 million according to a peer-reviewed survey in 1999.
White Sea and West Ice populations
Mature females usually give birth to one pup in March/April each year. The pups are born within well defined areas in the drift ice in the White Sea or in the area between Jan Mayen and East Greenland (the West Ice population). Harp Seals migrate in search for food over large areas in the Barents Sea, the Norwegian Sea, the Greenland Sea and the Denmark Strait.
The population size in 2000 was estimated to be more than 300,000 in the White Sea and 361,000 in the West Ice.
The annual prey consumption was in 2000 estimated to about 3.5 million tonnes in the White Sea area (Nilssen et al. 2000).
Each year, mature females (5–6 years old) give birth to a single pup, typically in late February. Pups weigh approximately 10 kg and are 80–85 cm long. Immediately after giving birth, the mother smells her offspring, and from that point on will only ever feed her own pup, whose scent she remembers. Harp Seal milk contains up to 48% fat, so pups gain over 2 kg per day when nursing, which lasts roughly 12 days. During this time the mother does not eat, and will lose up to 3 kg per day of body weight. Weaning is abrupt; the mother simply leaves and never comes back. The stranded pup will cry at first, and then become very sedentary to conserve body fat.
Pups are unable to swim or find food until they are about 25 days old, leaving them very vulnerable to polar bears and seal hunters. Due in part to the period of helplessness as infants, and to the long time it takes them to become proficient swimmers, as many as 30% of pups fail to survive their first year. Also, although it is not legal to catch seals using nets, thousands of seals are inadvertently killed in commercial fishing nets every year.
When the mother weans its pup, mature males (6–7 years old) roam around breeding with the females promiscuously. While courtship begins on the ice, the actual mating takes place in the water. Harp Seals have delayed implantation, meaning the fertilized egg becomes an embryo, but does not implant in the uterus right away. The embryo will float around for about three and a half months before implanting and beginning to grow. This allows all the females to give birth within a very small time window each year, when the ice pack is available for giving birth and raising their young.
Migration and vagrancy
Harp Seals are strongly migratory. The northwest population regularly moves up to 4,000 km northeast outside of the breeding season; one tagged individual of this population was recovered at sea off the north Norwegian coast, 4,640 km east-north-east of its tagging location. Their navigational accuracy is very high, with good eyesight being an important factor. They are occasionally found as a vagrant south of its normal range. In Great Britain, a total of 31 were recorded between 1800 and 1988, with one subsequently, on Lindisfarne in Northumberland in September 1995.
One recorded in the Shetland Islands in 1987 was linked to a mass movement of Harp Seals into Norwegian waters; by mid-February 1987, 24,000 were reported drowned in fishermen's nets and perhaps 300,000 (about 10% of the world population) had invaded fjords as far south as Oslo. The animals were in an emaciated condition and this was believed to be the result of food shortages, likely due to over-fishing by humans.
Harp Seals are opportunistic feeders, and will eat almost anything that is in great abundance. They have eaten massive amounts of Cod fish helping to decrease their number as well. It is estimated that each adult harp seal consumes 1.0-1.4 tonnes of fish annually, which translates to a consumption of 6 million metric tonnes each year by the North Atlantic population. This usually includes a wide variety of fish, still including Cod, and invertebrates, and their diet seems to vary during different stages of life. Since reporting of the stomach contents of killed seals began in 1941, at least 67 species of fish and 70 species of invertebrates have been found to be part of the Harp Seal's diet.
Predators include Polar Bears, Orcas, sharks, in some areas Walruses, while Humans are their primary predator. They have been hunted by humans for various products including fur, oil and meat for over 4,000 years, and more recently to mitigate their negative impact on local commercial fisheries.
- Whitecoats: Birth to 2 weeks
- Ragged jackets: 2 to 4 weeks
- Beaters: 4 weeks to 1 year
- Bedlamers: 1 to 4 years
- Spotted harp: 4 to 7 years
- Dark harp: mature/adult
In Canada, the season for the commercial hunt is from November 15 to May 15. The majority of sealing, however, 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". The hunting of whitecoats in Canada has been banned since 1987. In 2006, the St. Lawrence seal hunt officially started on March 25. This date was initially uncertain, due to thin ice conditions caused by the year's milder temperatures. Inuit people living in the region hunt them mainly for food and to a lesser extent, commercial reasons.
In 2003, the three-year quota granted by the Department of Fisheries and Oceans was increased to a maximum of 975,000 animals, with a maximum of 350,000 animals 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 for hunting by natives.
The Canadian seal hunt is monitored by the Canadian Government. However, although approximately 70% of Canadian seals killed are killed on "The Front", the vast majority of private monitors focus on the St. Lawrence hunt, due to its more convenient location.
Notes and references
- ^ Kovacs, K. (2008). Pagophilus groenlandicus. 2008 IUCN Red List of Threatened Species. IUCN 2008. Retrieved on 29 January 2009.
- ^ a b King, J. E. (1993). Seals of the World, 2nd. ed. British Museum, London.
- ^ a b c 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.
- ^ 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.