Population data are scarce for many species of marine mammals in the Barents Sea, making it difficult to identify population trends and their underlying causes.
Hooded and harp seals are both found in the West Ice and harp seals also breed in the White Sea. The most recent estimate for the West-ice group of harps seals is ~750 000 (2008) and the population is thought to be stable or increasing.
Recently, pup production in the White Sea harp seal population has been in decline, dropping from over 300,000 in 1998-2003 to 123,000 in 2008. Current (2007) abundance of the West Ice hooded seal stock was estimated to be ~82 000 animals, which is very low compared with historic numbers. The declining trends seen in both harp and hooded seal populations are probably caused by reductions in sea ice and other ecosystem changes related to climate warming.
Ringed seal reproduction has been negatively impacted by recent poor ice years in Svalbard (2006, 2007 and 2008), and the poor pup production is bound to cause declines in the adult population, with a time lag of a few years. For polar bears, population trends in the Barents Sea are unknown, but declines are expected in the coming decades. Walruses are thought to be increasing from the depressed conditions caused by hunting in the past, but the total population size of the whole Barents Sea is unknown as Russian areas have never been surveyed.
The white whale, or beluga whale, is the most numerous of the three resident, ice-associated arctic whales (white whale, narwhal and bowhead whale) in the Barents Sea. Their numbers have not been assessed, but this species likely numbers in the tens of thousands in the Svalbard/Barents Sea area. Narwhal have not been censused, but are certainly less numerous than white whales. The present number of bowheads belonging to the Svalbard stock is not known, but is presumably only in the tens or at most, in the low hundreds.
No systematic assessments have been conducted for bearded seals, but it probably numbers in the hundreds of thousands in the Arctic and certainly in the thousands in the Barents Sea,
Among the toothed whales, the long-finned pilot whale, the killer whale, the northern bottlenose whale and the sperm whale are summer visitors to the Barents Sea. The minke whale is the most numerous of the baleen whales that frequent the Barents Sea on a seasonal basis. Fin whales and humpback whales are second and third most abundant. In late summer in the northern Barents Sea, the distribution of baleen whales seems to be tightly linked to the capelin foraging migrations. Fin, humpback and minke whales generally occur along the northern front of the capelin migrations, avoiding areas with high capelin density.
The Norwegian coastal stock of harbour seals are subject to hunting or fishery related mortality, and current levels of mortality are thought to be unsustainable. Grey seals in the Norwegian part of the Barents Sea are subject to hunting levels that are not sustainable. Harbour porpoises are subject to by-catch in fisheries, and in order to sustain current levels of by-catch, immigration from outside the Barents sea is required.