Most of the marine mammal monitoring activity is focussed on either commercially important species or threatened species.
Different methods are used for abundance estimation of the commercially important marine mammal species in the Barents Sea. Mark-recapture experiments have been conducted for determining the abundance of harp seals since the mid 1980s (e.g. Øien and Øritsland, 1995).
More recently, the preferred method for estimating abundance of ice-breeding seals and pelagic cetaceans has become strip transect-surveys flown from aircraft for seals and done using ships for whales. Øritsland and Øien (1995) attempted the first survey of the West Ice in 1990/1991, but weather and ice conditions prevented calculation of a complete estimate. Since that time, aerial surveys have become more routinely conducted in the West Ice (Haug et al., 2006; ICES 2008), as the International Convention for Exploration of the Seas (ICES) now require that quotas for harvesting marine mammal species commercially be based on estimates which are less than 5-years old.
The first aerial surveys of harp seals in the White Sea were conducted in 1927-28 at the time of moulting (Shafikov, 2008). Breeding surveys to estimate pup production in the White Sea have been conducted in 1998, 2000, 2002, 2003, 2004, 2005, 2008 and 2009 (Potelov et al. 2003; ICES 2008), and moulting surveys of harp seals have been flown in 2001, 2002 and 2004 (Chernook et al., 2008). Compared to harp seals, hooded seals in the West Ice have received little monitoring attention, despite considerable levels of following the Second World War. The first successful aerial survey for hooded seals took place in 1997. New surveys were conducted in 2005 and 2007 (Salberg et al. 2008, ICES 2008). Regular monitoring of some marine mammals in the Barents Sea is carried out by sighting vessel surveys of cetaceans provide abundance estimates every 6 years. Regular monitoring sighting vessel surveys conducted by the Institute of Marine Research target minke whales and other large baleen whales. These vessel cruises are conducted annually, such that abundance estimates can be calculated for the overall region approximately every 6 years (Skaug et al. 2004).
Since 2002 the distribution patterns of marine mammals in the Barents Sea have been observed from research vessels during the ecosystem survey (see description of this survey above). In addition aircraft observations and observations from fishing and coastguard vessels with observers are used to explore the temporal and geographic distribution of some marine mammal species. Starting in 2002, the programme Monitoring of Svalbard and Jan Mayen (MOSJ) has documented sightings from scientific field parties and tourist operators in the Svalbard region on an annual basis, with particular focus on white whales, narwhal and bowheads. Additionally, aerial surveys are conducted within MOSJ to determine the abundance of polar bears, ringed seals and harbour seals every 5 years and walruses once per decade. On the coast of mainland Norway, harbour and grey seals are monitored every 5 years (Nilssen and Haug 2007; Nilssen et al. 2009).