During spring, harp seals exhibit a set sequence of activities: whelping (in March–April), followed by 12 days of intensive lactation, and then mating. The moult of adults and immatures takes place north of each whelping location after a lapse of approximately four weeks.
When the moult is over, the seals in the Northeast Atlantic disperse in large herds to feed, primarily along the ice edge, around Svalbard and in the northern Barents Sea. Occasionally, harp seals may occur in coastal waters of North Norway during winter and spring – in some years the number of visiting seals increases substantially and their distributional range extends to include the entire coast of Norway and parts of continental Europe. During the foraging season seals from Jan Mayen and White Sea stocks might overlap in distribution. The bulk of the harp seal diet is comprised of relatively few species, in particular capelin, polar cod, herring, krill and pelagic amphipods. The crustaceans appear to be of particular importance as harp seal food during the seals’ summer and autumn feeding, whereas later they appear to switch from crustaceans to fish. The annual food consumption by the White Sea population of harp seals in the Barents Sea has been estimated to be approximately 3.5 million tonnes.
The Greenland Sea (West Ice) stock of harp seals has been subject to commercial exploitation for centuries by German, Dutch and British companies – the Norwegian hunt started in 1846. Exploitation levels reached a historical maximum in the 1870s and 1880s when annual catches of harp seals varied from 50 thousand to 120 thousand. From 1971, the total annual catches have varied between a few hundred to about 17 thousand.
The initial sealing from the White Sea stock was shore based, taking place along the coasts of the White Sea and around the Kanin Peninsula, and presumably of a very small magnitude. Offshore hunting started in 1867, and the total catches soon increased to levels between 15 and 60 thousand up to around 1900, above 100 thousand after this year, and with the largest catches taken in the 1920s and 1930s (annual average of 200 thousand – 300 thousand animals). Since 1965, the annual catches have been regulated by catch quotas.
Stock status and regulations
The two Northeast Atlantic stocks of harp seals are commercially exploited and managed jointly by Norway and Russia. The stocks are assessed every second year by a Joint working group of the International Council of the Explorations of the Seas (ICES) and the North-West Atlantic Fisheries Organisation (NAFO). The assessment is based on modelling, which provides ICES with sufficient information to give advice on population status and catch potential. The inputs to the assessment model are pup production estimates, life history parameters and catch statistics. The population size for the Greenland Sea stock was in 2011 estimated to 649 570 seals. For the Barents Sea population the estimates was 1 364 700. The maximum catch quotas recommended by ICES are 25 000 (Greenland Sea) and 15 827 (Barents Sea) one year old and older seals.