Harp seals are migratory and have a much wider distribution range than ringed seals, bearded seals, and walruses; they also have a more pelagic life history (Lavigne and Kovacs, 1988; Haug et al., 1994a). Three different populations inhabit the North Atlantic: the Northwest Atlantic population off Canada’s east coast; the Greenland Sea (West-Ice) population which breeds and moults just north of Jan Mayen; and the East-Ice population which congregate in the White Sea to breed.
During spring (February-April), harp seals whelp on pack ice and then adults and subadults moult north of each respective whelping location after a lapse of ~4 weeks. Within the West-Ice population, these events occur primarily at fringes of the winter ice on the seaward side of thicker ice off the east Greenland pack (69-75 °N). Within the East-Ice population, these events occur in the White Sea and the south-eastern Barents Sea. When the moult is over, the seals disperse in small herds, feeding heavily to restore their blubber reserves. Some individuals from both Northeast Atlantic populations spread into the Barents Sea during summer and autumn months overlapping their ranges; their specific distribution in the Barents Sea mainly depends on the distribution of drifting pack-ice (Folkow et al., 2004; Nordøy et al., 2008). The body condition of animals that summer in the northern Barents Sea has recently declined (Øigard et al., 2013), presumably because of competition for food or changes in prey abundance. The West-Ice seals also spread through the drift ice along the east coast of Greenland, from Denmark Strait or farther south, towards Spitsbergen. The southward migration towards the breeding areas begins in November-December. The West-Ice and East-Ice populations have been commercially exploited and managed jointly by Norway and Russia over the past two centuries. The most recent estimate for the West-ice group is ~630,000 (ICES WGHARP, 2014) and the population is thought to be stable or increasing (ICES WGHARP, 2014). The Russian White Sea population has been monitored a long time; Dorofeev (1939, 1956), reported that aerial surveys performed on moulting grounds in 1927-1928 suggested that the White Sea population size at that time may have been 3.0-3.5 million individuals. While exploitation was low during World War II, the total hunting pressure increased substantially from 1946 onward (ICES WGHARP, 2008), and the population was probably reduced to 1.25-1.5 million individuals by the 1950s based on aerial surveys on the moulting grounds during 1952-1953 and 1959 (Surkov, 1957, 1963; Skaug et al., 2007). More recent pup production has been in decline, dropping from over 300,000 in during 1998-2003 to 123,000 in 2008 (ICES WGHARP, 2008). Reasons for the decline are not known, but it has been suggested that factors such as climatic conditions altering the ice cover in the White Sea, industrial activity including shipping and pollution effects, competition for krill and fish resources (i.e., capelin declines), and excessive hunting levels may all be contributing factors (Chernook and Boltnev, 2008; Chernook et al., 2008; Shafikov, 2008; Vorontsova et al., 2008; Zabavnikov et al., 2008; Øigård et al., 2013).