Harp seal

Harp seals in the breeding field in Newfoundland. On the left, a young seal (probably first-time mother) with incipient black side. On the right, an older seal with a large black panel on the side. Photo: Aqqalu Rosing-Asvid.
Harp seals in the breeding field in Newfoundland. On the left, a young seal (probably first-time mother) with incipient black side. On the right, an older seal with a large black panel on the side. Photo: Aqqalu Rosing-Asvid.
A harp seal's stomach contents with its favourite food, capelin. Photo: Aqqalu Rosing-Asvid.
Harp seal pup (whitecoat). Photo: Aqqalu Rosing-Asvid.
Harp seal pup (whitecoat). Photo: Aqqalu Rosing-Asvid.

Pagophilus groenlandicus

Size

The harp seal is a medium-sized seal. The pups are spotted, but around sexual maturation they get a black pattern on the back. Adult males grow on average to around 1.70m, females approx. 5cm shorter. However, there are some variations and the largest individuals grow to 2m. The first adult seals that medio May arrive in West Greenland from the breeding/moulting grounds near Newfoundland, are weighing around 80 to 90kg. They eat intensely during summer and fall and immediately before the breeding season which starts in February, the males weigh on average around 145kg and females about 130kg.

Food

The food along the west coast of Greenland up to Upernavik consists mainly of capelin (ammassat), supplemented with krill and various small fish. On the fishing banks in the open water areas, the relatively few collected stomachs of harp seal suggest that the sand lance found there are a very important source of food. North of Upernavik, harp seals eat mostly polar cod, supplemented by Themisto - (a kind of amphipod that mainly lives in the upper waters of open sea - see pictures in the ringed seal section). Food choice along the East Greenland coastline is unknown.

Reproduction

During the winter, the adult harp seals gather in specific areas where they give birth to their pups (see Distribution and numbers). The harp seal as a rule becomes sexually mature around 5 years of age, but significantly later sexual maturation has been reported in the most eastern harp seals during periods with few capelin. The pups are born around Newfoundland and in the White Sea from late February to early March. Births around Jan Mayen generally do not start before the latter half of March. At birth, the pups are around 80cm long and weigh about 10kg. They normally suckle for 10-12 days and during this period put on over 2kg per day. Mating normally takes place immediately after the suckling period. The fertilized egg divides a few times and becomes dormant. The egg does not attach itself to the womb (implantation) before late July or early August and then embryonic development begins.

Moulting

When the mating season is over, the males and the young animals are the first to gather together in large concentrations to moult. The females will often forage, i.e. seek food, for a few weeks before beginning to moult (shed hair).

Distribution and numbers

Distribution and numbers

After the moulting period, most harp seals from Newfoundland swim northwards. The males are the first to finish moulting and, along with the yearling pups (which do not moult), arrive at West Greenland around mid-May. During June-July, the females also turn up and, throughout the summer, young and adult harp seals spread northwards, both along the coast and in the open water in Baffin Bay. Some will also swim south of Greenland and up along the east coast a little, where they encounter other harp seals from the breeding grounds near Jan Mayen. The seals from Jan Mayen also spread eastwards and, in the Barents Sea, they mix with seals that breed in the White Sea. Harp seals make their way back towards the breeding grounds again in the autumn and winter as the ice is beginning to spread again. However, some, mostly the young animals, spend the winter along the south-west coast of Greenland.

Status

The commercial catch of harp seals started as early as the 1720s in the breeding grounds in the Greenland Sea off north-east Greenland (often near Jan Mayen) and around the 1760s around Newfoundland. Catches in these areas peaked in the middle of the 1800s but then slowed down gradually, as a result of overexploitation that reduced the population. In the early 1970s, there were about 300,000 individuals in the population around North-East Greenland and just under 2 million around Newfoundland. Since then, hunting regulations and a massive campaign against seal hunting and the use of sealskin in the 1980s helped to reduce the catch, so the population in recent decades has grown substantially. The most recent surveys, however, indicate that the strong increase has stopped, so that the population in the Vestatlantic and in the White Sea are stabilizing around their present level, whereas the population in the Greenland Sea is still increasing (see the figur).

Consultancy and management

Adult harp seals will most often forage in sculls during summer and fall. The prey of these scull will most often be capelin in southwest Greenland and polar cod in northwest Greenland. Photo: Aqqalu Rosing-Asvig

Advice on sustainable exploitation of harp seal is given by a working group under ICES / NAFO. The working group consists of researchers from Norway, Canada, Greenland and Russia. Populations are monitored by various means (see under research) and advise on sustainable harvest is given on the basis of that research.For many years in the Working Group calculated quotas that were no larger than those that would ensure that populations grew again, after centuries of overexploiting, but the populations are now so large that new guidance principles allow the individual countries to manage the seal based on ecological or socio-economic considerations.  For example, the quota could be increased depending on skin prices, as long as the population is not reduced to less than 70% of the maximum population.  If the population falls below 70% of the maximum population, a management plan should be initiated which aims to get the population over 70% again. If the population falls below 50%, strict protective measures should be introduced and if the population falls below 30%, all hunting should be stopped. This form of management should only apply to populations where there is a lot of reliable data. For populations with an inadequate data base, limits should be set so that restrictions on the catch are put in place earlier.

Research

The harp seal populations are monitored by counts of newborn pups on the breeding grounds with an interval of around 5 years. The reproduction rate among adult females is also monitored. Close to 100% of the adult females were giving birth during the years with a reduced population, but the rate of parturition decreased with an increase in the population size and in recent years it has fluctuated so that only 30-80% of the adult females have been given birth. The seals apparently aborts if they are not fat enough to provide the pup with a sufficient layer of blubber. The females have also become older before they start to give birth. Survey estimates of pup production are put into a model together with estimates of fecundity, the age-composition in the population, the catch numbers and the age-composition of the catch and estimates of early mortality among the pups due to bad ice-conditions.

The model give an estimate of the total number of seals in the population. It "learns" something as more new data are added and the uncertainty is therefore largest on the most recent figures. These numbers are likely to change slightly and the uncertainty will decrease as new data are added.

The model shows that the population no longer is growing and this change is mainly due to the declining birth rate.

 

 

The model shows that the population no longer is growing and this change is mainly due to the declining birth rate.
A harp seal's stomach contents with its favourite food, capelin. Photo: Aqqalu Rosing-Asvid.
Updated 01.16.2017