Harp seal

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The Harp Seal (Phoca groenlandica, also named Pagophilus groenlandicus), is a marine mammal of the family Phocidae that is found in the North Atlantic and Arctic Oceans. Average lifespan for a harp seal can be up to 35 years.

Population

Harp Seal separates into two populations that breed in different locations: the White Sea, the West Ice and the Northwest populations, of which the Northwest Atlantic population near Newfoundland, Canada is the largest. This population is genetically different from the two others which are not proved genetically different from each others. All three populations are hunted commercially, mainly by Canada, Norway, Russia and Greenland.

The Northwest population

The Northwest population historically was greater than 30 million, but the population declined by 50–66% between 1950 and 1970 due to commercial hunting in Canada, and by 1970, was in serious trouble. Since 1970 it has nearly tripled in size to 5.2 million according to a peer-reviewed survey in 1999. Harp Seals eat a wide variety of fish and other sea creatures, 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. After the Canadian cod collapse many French fishermen and politicians blamed Harp Seals for the destruction and hindering the recovery of the North-West Atlantic Cod population. Although cod is a major contribution to Harp Seals diets, most of the cod is Arctic Cod and not the commercial Atlantic. The ratio is about 36:10 although the total tonage of cod is around 200,000 tonnes. Although the effect of harp seals on the recovery of the cod stocks is disputed, it is widely accepted that harp seals did not cause the collapse. The issue with most regarding the cod stocks is that if the dancing were to stop, the population would grow and therefore cause total prey consumption to increase. Even with heavy hunting, from 1990 to 1999 there was a 800,000 tonne (or 32%) increase. If the hunt were to stop, the belief is that population would skyrocket and within a few years more then likely doubling the consumption rate. The Harp Seal is at the top of its food chain and has few natural predators to keep the population at bay. For more information, review [Northwest Atlantic Harp Seals Stock Status Report 2000] from the Canadian Government.

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 seal 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 50% 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 very 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 humans during this time.

As mother Harp Seals wean their young, mature males (6–7 years old) roam around breeding with the females promiscuously. Courtship begins on the ice; however 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.

Adult Harp Seals grow to 1.7 m long, can weigh over 130 kg, and live up to 35 years. Polar Bears, sharks, Orcas, and in some areas Walruses are natural predators of Harp Seals. 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.

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). The Harp Seal is migrating searching for food over large areas in the Barents Sea, the Norwegian Sea, the Greenland Sea and the Denmark Strait. Age of maturation is 4–8 years, normal life length more than 30 years. An adult animal is about 1.9 m long with a weight around 200 kg.

The population size was in 2000 estimated to more than 300,000 animals in the White Sea and 361,000 animals 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).

Features

Harp seals resemble harbor seals in body and head form, but are larger.

• “Whitecoats” = Birth
• “Ragged Jackets” = 2-4 weeks
• “Beaters” = 4 weeks to 1 year
• “Bedlamers” = 1 to 4 years
• “Spotted Harp” = 4 to 7 years
• “Dark Harp” = mature

Hunting

(See main article: Seal Hunting)Adult seals eat crusteaceans and fish, but the young mostly eat crabs and their mother's milk.

Notes and references

 

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