Harp seal (Pagophilus groenlandicus)

A large number of harp seals laying on small ice floes.
Photo: Andrea Taurisano / Norwegian Polar Institute

Harp seals are monitored because the population can be affected by hunting and the species is dependent upon ice and may be affected by climate change. There is still a harp seal hunt in both the West Ice and the East Ice. Modelling suggests that the stock has declined greatly in the East Ice, but has grown in the West Ice.

What is being monitored?

Production of pups and estimated population size

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In the first 2 decades after the Second World War, the harp seals in both areas were far too heavily harvested. The stocks therefore declined right up to the end of the 1960s, when the hunting was regulated. This, combined with a decline in the hunting effort during the 1970s, had a positive effect on both stocks, which immediately began to grow. The estimates for the East ice after 2004, however, indicate a significant reduction in pup production, which has so far not been satisfactorily explained.

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In the first 2 decades after the Second World War, the harp seals in both areas were far too heavily harvested. The stocks therefore declined right up to the end of the 1960s, when the hunting was regulated. This, combined with a decline in the hunting effort during the 1970s, had a positive effect on both stocks, which immediately began to grow.

Status and trend

The harp seals in the northeastern Atlantic Ocean are regarded as distinct from the Canadian harp seals. The pups are born in March-April on the pack ice in 2 well-demarcated areas:

  1. Around Jan Mayen (the West Ice)
  2. In the southeastern Barents Sea and the White Sea (the East Ice)

Harp seals are pelagic outside the pupping season, mainly in areas with pack ice. Long foraging migrations are undertaken. Seals from both the West Ice and the East Ice are found in the Svalbard area in summer and autumn.

The West Ice

When the West Ice stock was modelled in 2016, estimates were used for pup production from tagging and recovery trials undertaken during 1983–1991 and aerial censuses from 2002, 2007 and 2012. Modelling based on these figures gave an estimated production of 106,580 pups (95% confidence interval 76,500–136,400) and a stock of 553,800 seals over one year old (1+) (95% confidence interval 366,500–719,400) in 2016. This gives a total stock of around 650,000 individuals (95% confidence interval 470,000–830,000).

ICES has calculated that sustainable catches for 2017 and the coming years are 21,500 one-year-old and older animals, or an equivalent number of pups (where 2 pups approximately equates with one 1+ seal).

The East Ice

In the East Ice, Russian aerial censuses that were performed in the White Sea in 1998, 2000 (two independent censuses), 2002, 2003, 2004, 2005, 2008, 2009, 2010 and 2012 gave 11 independent estimates for pup production in this harp seal stock.

The estimates from 2005 and 2008 are uncertain, particularly because the censuses were performed so late in the season. This may have helped to produce the very low figures.

The estimates from 2004, 2009, 2010 and 2013, however, indicate a substantial reduction in the pup production in this stock. So far, there is no satisfactory explanation for this, but the fertility of the females seems likely to have been reduced. Difficult ice conditions in the White Sea since 2003 may also have contributed to the reduction. Perhaps part of the stock has moved to new, so far unknown, pupping sites beyond the White Sea.

Modelling using these input data gave an estimated production of 211,000 pups (95% confidence interval 185,100–236,900) and a stock of 1,197,000 animals over one year old (1+) (95% confidence interval 1,042,800–1,351,200) in 2016. This gives a total stock of around 1,408,000 individuals (95% confidence interval 1,250 000–1,565 000).

ICES has calculated that sustainable catches for 2017 and the coming years are 10,090 one-year-old and older animals, or an equivalent number of pups (where 2 pups approximately equates with one 1+ seal).

Causal factors

Catch quotas are set every other year based on calculations of the total stock and what are referred to as sustainable catches, which are the catch volume it is assumed will stabilize the stock.

The ICES Advisory Committee for Fishery Management (ACFM) regards the catch in both the West Ice and the East Ice as being within safe biological limits. There are no comparable data for the stock size and access to food to permit a discussion of such relationships.

Consequences

The harp seals in the East Ice and the West Ice were far too heavily harvested during the first two decades after the Second World War. The stocks therefore declined in size right up to the end of the 1960s, when regulation of the hunting was introduced. This, combined with a declining hunting effort during the 1970s, had a positive effect on both stocks, which immediately began to grow.

The harp seal stock in the West Ice still seems to be growing steadily, whereas pup production in the East Ice has shown a substantial reduction since 2003. The most recent censuses in the East Ice seem to indicate a slight increase. Further monitoring is required to be able to say anything definite about the trend in the East Ice.

The total consumption by the seal population can be calculated based on knowledge of feeding habits (acquired on special cruises and from catches) and the size and demography of the population. It has been calculated that, in the course of one year, the East Ice stock consumes about 3.5 million tons of various prey in the Barents Sea.

About the monitoring

Harp seals are monitored because the population can be affected by hunting and the species is dependent upon ice and may be affected by climate change. Commercial catching of harp seals takes place in the East ice (Norway and Russia) and the West Ice (Norway). The population monitoring has largely had the objective of providing a basis to set hunting quotas.

The most important basis for the recommendations has been estimates of the pup production, based on counts and tagging and recovery experiments. This approach is chosen as it is easier to count pups during the limited breeding season than to count adult seals. Pups remain on the ice during counting, but adults may enter the sea. Hence, methods to calculate total populations are indirect (model calculations) based on supplementary knowledge from other studies on reproductive status with the females.

In addition to being a harvesting resource, the harp seal is abundant and is able to consume large quantities of fish from the fish stocks in the Greenland Sea, the Barents Sea and the waters surrounding Svalbard. Hence, its feeding behaviour and fish consumption is being monitored, to estimate its influence when estimating fish mortality in important fish stocks (e.g. capelin). Knowledge of the size and demography of the population is needed to calculate its total consumption of fish.

Places and areas

Relations to other monitoring

Monitoring programme
International environmental agreements
Voluntary international cooperation
Related monitoring