The genus name for Hooded Seals has been either Phoca or Cystophora with various combinations of species names including cristata, cucullate, borealis, leucopla, mitrata and isidorei (reviewed in Kovacs and Lavigne 1986). Most of the taxonomic confusion arose from different sex and age classes being thought to be different species in the 1700s and 1800s. Young Hooded Seals were even classified as being a type of Monk Seal by Gray (1848).

Morphometric and allozyme analyses, as well as molecular genetics analyses, suggest that Hooded Seals are a single panmictic population (Wiig and Lie 1984, Sundt et al. 1994, Coltman et al. 2007). However, there is some uncertainty regarding this conclusion because of field sampling (timing) issues potentially mixing animals from the various breeding sites, and current genetics work is ongoing. Management is conducted based on recognized breeding stocks (Sergeant 1974, Kovacs and Lavigne 1986, Lavigne and Kovacs 1988, ICES 2019) - Gulf of Saint Lawrence, the Front (east coast of Canada) and Davis Strait - and the West Ice (northwest of the island of Jan Mayen).

European regional assessment: Vulnerable (VU)

Hooded Seals breed in a single location in the European mammal assessment area—on drift ice occurring west of Jan Mayen Island. This stock has been reduced from more than 1.2 million animals to ca 77,000. This 85% reduction has largely been due to overhunting from 1960–2007 (ICES 2019). However, despite complete protection from commercial harvesting since 2007, the stock is continuing to decline (ICES 2023). Greenlandic subsistence hunting is ongoing (NAMMCO catch database); with some of the removals in East Greenland coming from this European region stock. Overharvesting of Redfish (Sebastes spp.) in Norwegian coastal waters might also play a role in the lack of recovery of the stock (Artsdatabanken 2021). But climate change-induced reductions in their breeding and resting habitats, with concomitant shifts in the drift ice towards Greenland where Hooded Seals are exposed to high Polar Bear mortality, are the key threats (Kovacs et al. 2011, 2012; Øigård et al. 2014, Stenson and Hammill 2014, Kovacs et al. 2021).

Hooded Seals in the European Arctic qualify for a classification as Vulnerable (VU) VU under A2ab based on a decline of c.38% in pup production estimates over the past three generations (38.4 years). This ongoing decline is expected to continue in the future due to increased levels of predation and further habitat declines. However, pup production estimates are uncertain and method-dependent, and back-casting over the past 30 year period suggest a 40–50 % decline, and the species should be reassessed when improved pup production and N1+ data are available. Breeding habitat has clearly declined by at least 50% over the past 3GL period and the decline is escalating, however, a future population decline has not been estimated here, but may result in significant future declines, potentially qualifying the species as Endangered under criteria A3c due to extreme breeding habitat losses (in excess of 50%).

Clarification of population structure across the whole of the North Atlantic range, as well as improved estimates of N1+ numbers in non-European population segments, would help facilitate conservation assessment needs for the species.

Hooded Seals are found throughout the North Atlantic, extending into drift ice areas within the Arctic Ocean (Kovacs 2018). Animals from the West Ice stock, which constitutes the European stock, reside in the Northeast Atlantic, ranging from mid-Norway in the south almost to the North Pole (Vacquie-Garcia et al. 2017, Hamilton et al. 2021).

However, Hooded Seals wander widely and are registered as vagrants along European coastlines as far south as Portugal and the Canary Island. North America vagrants have been registered from New England south into the Caribbean; several Pacific occurrences have also been reported, as far south as California (Mignucci-Giannoni and Haddow 2002, Harris and Gupta 2006). During years with little sea ice strandings in the St. Lawrence River area are common; this phenomenon seems to be increasing (Trunchon et al. 2013). These North American registrations of Hooded Seals likely stem from Northwest Atlantic stocks, rather than the European one.

Hooded Seals are managed as two stocks, split into the Northwest Atlantic (with its three breeding areas) and the Northeast Atlantic, comprising the only European stock, which breeds near Jan Mayen Island (ICES 2019, 2023). This population is referred to as the West Ice group, or more commonly in recent times – the Greenland Sea stock.

In European waters, Hooded Seals have experienced a precipitous decline since the 1950s. Many surveys have taken place in recent years for Greenland Sea Hooded Seals. In 1997, pup production was estimated to be 24,000 (14,800-32,700) and the one-year-old+ population size was estimated to be 100,000-110,000. In 2005, pup production was estimated to be 15,200 (CV = 0.25). This decline was supported by a survey in 2007 that estimated a pup production of 16,140 (CV = 13.30%) (Øigård et al. 2010). In 2012, pup production was estimated to be 13,655 (CV = 13.90) (Øigard et al. 2014). A survey flown in 2018, had an estimate of 12,977 (CI = 9.87–17.07) pups (Biuw et al. 2019, ICES 2019). Surveys were conducted once again in 2022 with a resulting pup production estimate of 13,509 (CV = 12.90%). Using the pup production values along with updated biological parameters for reproduction, a total population size of 76,832 (60,262-98,009) was estimated for 2022 demonstrating that the Greenland Sea Hooded Seal population is continuing to decline despite the cessation of commercial harvests (ICES 2023). Based on pup production figures, a decline of 38.1% over the past three generation lengths (1984 to 2023) has been calculated.

No new data on the abundance/trends of Hooded Seals are available for the Northwest Atlantic; the last survey was carried out in 2004-2005 (Hammill and Stenson 2006). The largest group in Canadian waters occurs on the Front while the breeding groups in the Gulf and Davis Strait are considerably smaller. The Davis Strait group declined from a pup count of 18,600 in 1984 to 3,300 in 2005 (Stenson et al. 2006) and 2024 surveys found no animals breeding in the Davis Strait (C. Hamilton pers. comm.; survey will be repeated in 2025 in this region). The overall Northwest Atlantic population was at the time of the last survey, two decades ago, c.600,000 animals.

Hooded Seals are a strongly ice-associated species that breed on drift ice (Lavigne and Kovacs 1986). They spend a lot of time in ice-filled waters outside the breeding season, but they also undertake extensive migrations within the North Atlantic, sometimes occupying pelagic areas without sea ice (Vacquie-Garcia et al. 2017, Hamilton et al. 2021).

They are a markedly sexually dimorphic species. Adult males average 2.5 m in length and weigh an average of 300 kg (Kovacs and Lavigne 1986), with very large animals reaching over 400 kg (Kovacs et al. 1996). Adult females are smaller, averaging 2.2 m and 236 kg (ranging up to over 300 kg) (Kovacs and Lavigne 1992). Hooded Seals give birth on drifting pack ice in late March and early April. They choose the heaviest available floes in quite dense ice areas (Kovacs 2018). The breeding season for this polygynous (serially monogamous) species is very short, usually lasting about two weeks in total within a population (Kovacs 1990). Mating takes place in the water. The generation length is estimated to be 12.8 years (Pacifici et al. 2013), giving a three-generation length period of 38.4 years.

This species has the shortest lactation period for any mammal with most pups being weaned in four days (Bowen et al. 1985). During the nursing period they grow extremely rapidly, gaining seven kg per day and doubling their birth mass by the time of weaning (mean weaning mass 47 kg, Kovacs and Lavinge 1992). This amazing growth is achieved by drinking an average of 10 kg of milk daily, with very high efficiency of transfer of energy from maternal blubber through milk and into pup tissue (Lydersen et al. 1996).

In the Greenland Sea population, animals congregate in the Denmark Strait or in drift ice areas northwest of Jan Mayen for both breeding in spring and again in early summer for moulting (usually somewhat further north than breeding), followed by dispersal across the North Atlantic (Folkow et al. 1996, Vacquie-Garcia et al. 2017). During the breeding and moulting periods Hooded Seals congregate in loose herds on the sea ice, but at other times of year they tend to be solitary although food aggregations can lead to small groups being seen in the northern reaches of Svalbard (Storrie et al. 2018, Bengtsson et al. 2021). Longevity is normally 25-30 years (Kovacs 2002).

Hooded Seals are extreme divers. Although most dives are from 100-600 m deep and last 5-25 minutes, very deep dives to over 1,000 m and dives lasting almost an hour have been recorded (Folkow and Blix 1999, Folkow et al. 2010, Andersen et al. 2013, Vacquie-Garcia et al. 2017). Age and sex classes show somewhat different foraging habitat preferences that result in different diving patterns (Andersen et al. 2009, 2013; Vacquie-Garcia et al. 2017). Hooded Seals feed on a wide variety of fish and invertebrates including Greenland Halibut, gadid fishes such as Atlantic Cod (Gadus morhua) and Polar Cod (Boreogadus saida), Redfishes (Sebastes spp.), Herring (Clupea harengus), Capelin (Mallotus villosus), Squid (Gonatus fabricii), and shrimps (Pandalus borealis) (Haug et al. 2004, 2007). Polar Bears, Killer Whales, and Greenland Sharks are known to prey on Hooded Seals (Leclerc et al. 2012, Foote et al. 2013, McKinney et al. 2013, Øigård et al. 2014, Kovacs 2018).

Ice conditions in the areas used for breeding and moulting have been and are deteriorating, and a continuing decline in habitat extent and quality is observed.

Sea ice losses have been extreme in the Hooded Seal breeding areas (57% thickness reduction, reduction in extent of c.40%) used by this population over recent decades and projections for the future suggest the declining trend will continue (Estathiou et al. 2022, Sumata et al. 2022).

Hooded Seals were subjected to intense commercial hunting in the 19^th and 20^th centuries. Harvests were often conducted in association with Harp Seal harvests and commercial fisheries for Greenland Sharks. Norway, the former Soviet Union, Canada, and Greenland, have all been involved in these commercial harvests. Following World War II, the hunt focused largely on pups because of their highly prized blue-back pelt, however, many adult females were taken when defending their pups (Sergeant 1976). Annual harvests of Hooded Seals continue in Canada (pups are protected) and Greenland; Greenlandic harvests are the largest (ICES 2019). The Davis Strait breeding population has likely been reduced by Greenlandic hunting on the west coast (perhaps to extinction) and currently the East Greenland subsistence catch likely is in part from the Greenland Sea stock.

Bycatch of Hooded Seals in coastal net fisheries has been reported from the United States, from trawl fisheries off Norway and Newfoundland, and salmon drift nets used off Greenland (Reeves et al. 1992, Waring et al. 2005, Woodley and Lavigne 1991), but it is not thought to be a major cause of mortality. Competition for food with commercial fisheries and other predators has been suggested as a factor that may limit population growth or lead to declines (Reijnders et al. 1993). The Barents and Norwegian Sea Redfish stocks declined markedly in the 1990s which might have impacted food availability for Hooded Seals. Currently, declining Polar Cod (Boreogadus saida) stocks are a concern for Hooded Seals in the Northeast Atlantic (Enoksen et al. 2017).

Impacts of oil spills on Hooded Seals have not been reported but given the Hooded Seals ice breeding habit, there might be at risk of mortality from spills during the pupping season when newborn and newly weaned pups could be fouled (St. Aubin 1990). Hooded Seals are not known to have suffered fatalities during the mass die-off of Harbour Seals in European waters from phocine distemper virus in 1998 and 2002, but subsequent testing of a variety of Arctic seals revealed antibodies to the virus in 18-24% percent of the Hooded Seals sampled, indicating exposure and transmission of the virus (Harkonen et al. 2006). Hooded Seals in the Northeast Atlantic have high organohalogen contaminant burdens, which are thought to be high enough to cause thyroid disruption (Villanger et al. 2013).

Climate change is a serious threat to this ice-breeding species (Tynan and DeMaster 1997; Kovacs et al. 2011, 2012; Laidre et al. 2015, Kovacs et al. 2021). Sea ice losses have occurred throughout the species’ range over the last few decades (e.g. Stenson and Hammill 2014, Spreen et al. 2020), with complete ice failure in the southern parts of the range in the Northwest Atlantic being increasingly common (Johnston et al. 2005). Reduction in ice cover in the Greenland Sea has resulted in smaller floes and less stable ice conditions that likely impact survivorship of pups. Additionally, pupping areas have more open water and they have shifted closer to the Greenland. The occurrence of Hooded Seals has increased in the diet of both Polar Bears and Killer Whales in East Greenland concomitant with these sea ice changes (Foote et al. 2013, McKinney et al. 2013, Øigård et al. 2014). Polar Bear predation on Hooded Seals in East Greenland has increased 9.5% per decade since the mid-190s (McKinney et al. 2013). It is thought that this source of mortality is possibly becoming a driver of the declining population trend of Hooded Seals in the Greenland Sea (Øigård et al. 2014).

An indirect result of climate change is that prey abundance and distribution is undergoing significant change, with “borealization” of the community in the Barents Region that is likely having negative impacts on Hooded Seals (e.g. Beaugrand et al. 2009, Fossheim et al. 2015, Christiansen 2017, Enoksen et al. 2017). A recent dietary study on Greenland Sea Hooded Seals found that their diet is dominated by Polar Cod (Boreogadus saida) and despite Hooded Seals seeming to be able to do some prey shifting, Enoksen et al. (2017) concluded that Greenland Sea Hooded Seals show narrow niche breadth and specialization on Arctic fishes that are suffering negative impacts of climate change. Increased fishing, disease risks, shipping, mining, ocean noise etc in areas previously ice covered, but now open, increase the general risk level for this species (Pagnan 2000, PAME 2019). Ecological change within the system is seen as the likely cause of declines in Hooded Seal numbers (Frei et al. 2012, Biuw et al. 2022).

Hooded Seals were subjected to intense commercial hunting in the 19th and 20th centuries. Harvests were often conducted in association with Harp Seal harvests and commercial fisheries for Greenland Sharks. Norway, the Soviet Union (now Russia), Canada, and Greenland have all been involved in the commercial harvests of this species. Following World War II the hunt was primarily focused on pups because of their highly prized blue-back pelt, however, many adult females were taken while defending their pups until killing of mothers in the breeding areas was prohibited in the various areas (Lavigne and Kovacs 1988).

The abundance estimate for Hooded Seals in the Northwest Atlantic is now a decade old; the last survey was conducted in 2005 (ICES 2019), and the stock is now treated as a data-poor stock in terms of management protocols. Total allowable catch was set at 8,200 in 2007 and has remained unchanged despite the lack of new information on stock sizes or trends in the region. However, Canadian catches are reported to be very low, some few 10s of animals per year.

Hooded Seals are also harvested in Greenland at a current level of a few thousand animals per year. It is assumed that most of those animals are from the Northwest Atlantic breeding groups (Davis Strait, Gulf, and Front) given that most of the harvest takes place in West Greenland. However, some animals are also taken on the east coast of Greenland, and these animals are likely from the (European) West Ice stock.

Hooded Seals have been harvested in the West Ice (Greenland Sea, north of Jan Mayen) for centuries. This hunt increased substantially after World War II, to levels that were clearly not sustainable. Regulatory measures were introduced in 1958 to reduce effort, and quotas were imposed in 1971 (Sergeant 1976). Based on catch per unit effort analyses and mark-recapture pup production estimates it was assumed that the stock increased from the 1960s through to the 1990s at an unknown rate (Ulltang and Øien 1988). In hindsight this almost certainly was not the case. Aerial surveys in 1994 failed to produce an abundance estimate (Øritsland and Øien 1995). Recent modelling efforts suggest that a very substantial decrease in population abundance took place from the late 1940s up to the early 1980s (ICES 2019). This decline has continued through to the present and predictions suggest an ongoing decline of 7% over the coming decade (Øigård et al. 2014). Total pup production in this stock was estimated to be 24,000 in 1997 and this number dropped to 15,250 in 2005 (Salberg et al. 2008) and has continued to decline to 13,655 in 2012, despite a complete cessation of commercial harvesting (Øigård et al. 2014).

The species is listed on Annex V (animal and plant species of community interest whose taking in the wild and exploitation may be subject to management measures) of the EU Habitats Directive (Council Directive 92/43/EEC of 21 May 1992 on the conservation of natural habitats and of wild fauna and flora - consolidated version 01/01/2007) and on Annex III (protected fauna species) of the Bern Convention (the Convention on the conservation of European wildlife and natural habitats).

Numerous conservation measures, international management plans, harvest quotas and restrictions, as well as agreements and treaties, have been developed for the conservation of Hooded Seals dating back to the 1870s (Sergeant 1976).

In European waters, harvest quotas were implemented at Jan Mayen in 1971 and complete cessation of the commercial harvest was enacted in 2007 (2008 hunting season closure). The ICES/NAFO/NAMMCO Working Group on Harp and Hooded Seals (WGHARP) models population numbers from surveys and provides advice for management. Based on surveys conducted in 2022 and new biological parameter data, zero quota is recommended (ICES 2023).

Hooded Seals are classified as Vulnerable on the Global IUCN Red List (Kovacs 2016) and are Endangered on the Norwegian Red List (Eldegard et al. 2021); the latter assessment is done for the European Hooded Seal stock.

A global assessment of population structure would help in the assessment process. More robust N1+ estimates are needed for all stocks. Ongoing survey efforts are required to track impacts of climate change and population trends.