European regional assessment: Least Concern (LC)

This species is widespread and abundant, and European populations are stable or increasing. Consequently, European populations are classified as Least Concern.

Grey Seals have a cold temperate to sub-Arctic distribution in North Atlantic waters over the continental shelf (Hall 2002). There are three populations isolated both geographically and by the timing of reproduction (Bonner 1981); mtDNA differences are large between these three breeding areas, though the Baltic and Northeast Atlantic populations are much closer to one another than to the Northwest Atlantic population (Boskovic et al. 1996). In the western Atlantic, the population is centred on the eastern Scotian Shelf off northeastern North America, but the Grey Seal ranges from the Gulf of Maine to southern Labrador, including the Gulf of St Lawrence (Lesage and Hammill 2001). The northeast Atlantic population is concentrated around the UK and Ireland but is also found around Iceland, the Faroe Islands, and along the European mainland coast from the Kola Peninsula (Russia) south to southern Norway, and from Denmark to Brittany in France. The Baltic Sea subpopulation is confined to the Baltic Sea (Bonner 1981, Hall 2002). Vagrants are known from as far south as New Jersey in the western Atlantic and Portugal in the eastern Atlantic (Rice 1998).

The centre of abundance of the Eastern Atlantic Grey Seals is around the UK. The main UK colonies are in Scotland’s Outer Hebrides, Orkney and Southeast England. There are also breeding colonies across the rest of the UK. Although the number of pups born has grown steadily throughout the UK, there is clear evidence that the population’s growth rate is levelling off in all areas except the central and southern North Sea where growth rates remain high. Grey Seal population trends in the UK are assessed from the counts of pups born during the autumn breeding season (Russell et al. 2019). The most recent (2019) estimate of Grey Seal pup production in the UK was 67,850 (95% CI 50,250-85,400; SCOS 2021). Pup production, along with scaled haul-out counts in August, are used to estimate total non-pup population size using a Bayesian state-space model resulting in an estimate of 140,700 (95% CI: 129,300-153,500) in 2020(SCOS 2021). 

The latest aerial census to estimate the status of the Grey Seal population in Iceland was conducted in 2017. The total population size was estimated to be 6269 (95% CI: 5375–7181) (Granquist and Hauksson 2019). A population modelling study has indicated an increase in abundance of the Norwegian Grey Seal population during the last 30 years, with a total of 8,740 (95% CI: 7,320–10,170) animals estimated in 2011 (Øigård et al. 2012, NAMMCO 2016). However, new boat-based surveys carried out in 2014–2015 did, indicated a significant decrease in the grey seal pup production compared with the counts in the period 2007–2008, likely due to high levels of by-catch in the monkfish fishery.

There is no current information on the abundance or trends in the number of grey seals in the White Sea. Grey seals are rapidly increasing in abundance in the Wadden Sea (Danish, German and Dutch coasts) with 9,069 during the moulting period in spring 2021 (Brasseur et al. 2021).

In France, the most recent data available was a count of 6,269 grey seals in 2021 (ICES 2022). Grey seals in the Baltic Sea are recovering after a century of bounty hunting and several decades of low fertility caused by environmental pollution (Harding et al. 2007). The population has continued to increase with 42,000 counted in 2021 (HELCOM EG MAMA).

Grey Seals are large sexually dimorphic phocids. In the United Kingdom, adult males are on average 2.07 m long and weigh an average 233 kg, with a maximum of 310 kg. Adult females average 1.8 m in length and have a postpartum body mass of 185 kg (Pomeroy et al. 1999). At birth, pups are 90-105 cm, with male pups averaging 15.8 kg and female pups averaging 14.8 kg in weight (Bonner 1981). Pup weaning weights average 45 kg for males and 41 kg for females. Pupping occurs from September to March with peak dates differing significantly between populations: in Eastern Atlantic, September-December; and in the Baltic Sea, late February to early March, which probably reproductively isolates each group (Bonner 1981). Pups are born on land in the Eastern Atlantic and ice in the Baltic Sea (Bonner 1981). Pups are born with a woolly lanugo that is molted several weeks after weaning. Lactation lasts 17 days on average and weaning is abrupt (Pomeroy et al. 1999). Pups undergo a post-weaning fast on land of about three weeks during which they lose 24% of their body weight (Reilly 1991, Noren et al. 2008). Males do not defend a fixed territory, rather they defend individual or small groups of females until they mate with those females and then move on to other females (Anderson et al. 1975). Larger males generally stay longer in the colony and have higher reproductive success than smaller males (Anderson and Fedak 1985). Survival is age dependent in males and females, but throughout life adult females have higher survival than adult males (0.988 vs 0.904, den Heyer and Bowen 2017). Survival in the first year of life and to recruitment is positively related to pup size at weaning (Hall et al. 2001; Bowen et al. 2015).

Grey Seals do not undertake long-distance migrations but do exhibit seasonal dispersal throughout their range. In one study, they spent 43% of their time within 10 km of frequently used haul-out sites, traveling to sandy areas, or gravel sea-bed sediments, the preferred habitat of sandeels, an important part of the Grey Seal’s diet. Short trips away averaged 2.3 days (McConnell et al. 1999). More recent research indicates that Grey Seals often forage in the same areas within 100km of a haulout site although more distance foraging also occurs (Russell et al. 2013, 2015) with occasional long trips of up to 2,100 km, crossing from northern England to Shetland or Orkney, and from the Faroes into the North Sea. In the Baltic Sea, Grey Seals make short trips, spending roughly 75% of their time within 50 km of haul-out sites (Sjoberg and Ball 2000).

Grey Seals are generalist predators feeding mainly on a variety of pelagic and benthic fish species at depths of up to 100m, although they can feed at all the depths found across the UK continental shelf (Smout et al. 2014; SCOS 2020). They consume a wide variety of prey including sandeels (usually the dominate prey), gadoids (cod, whiting, haddock, ling), and flatfish (plaice, sole, flounder, dab) (Prime and Hammond 1990). Diet varies seasonally and from region to region (Wilson and Hammond 2019).

In the Eastern Atlantic, Grey Seals are abundant upper-trophic level consumers. They are potential competitors with harbour seals as their diets overlap (Wilson and Hammond 2019). In some areas, at sea movement data show that Grey Seals use offshore areas connected to their haul-out sites by prominent corridors, whereas harbour seals primarily stay within 50 km of the coastline. Both species show fine-scale offshore spatial segregation off the east coast of Britain and broad-scale partitioning off western Scotland (Jones et al. 2015). Grey Seals also interact with fisheries. In the West of Scotland, estimates of cod consumption by Grey Seals have exceeded reported catches and spawning biomass. A simple population model was used to identify the likely direction of cod population change at recent mortality rates (Cook et al. 2016). The analysis suggests that predation by grey seals can be an important component of the total stock mortality. Increasing seal populations in central and southern North Sea are likely to increase levels of interactions between seals and fisheries in the region (SCOS 2020). Depredation of salmon by Grey Seals from coastal static net fisheries represented a significant economic loss to the fisheries concerned and an additional source of mortality for salmonids, a source of mortality that is probably largely dependent upon the presence of the net fishery. Grey Seals have few natural predators but are known to be taken by killer whales (Wier 2002) and presumably large sharks as reported for the northwest Atlantic subspecies (Bowen 2011).

Grey Seals have been important in subsistence harvests throughout the history of their contact with humans. They have been hunted by peoples of the Baltic Sea coast for more than 10,000 years (Harkonen et al. 2005). Overharvesting in the Baltic in the early 20^th century led to a large decline, from a population that once numbered an estimated 30,000 to perhaps as high as 200,000 to a low of 1,500-2,000 by the early 1980s (Kokko et al. 1999).

Government culls, bounties, and licensed kills for harvest and protection of fishing gear have been put into effect in many countries (Bowen and Lidgard 2013), and continue to be used in some in efforts to control Grey Seal numbers and reduce their impact on commercially important fisheries. Grey Seals feed on some commercial species, and by damaging nets and traps, they are in direct conflict with fisheries. Grey Seals are the terminal vector for seal worm life cycle, also known as cod worm, a destructive parasite of groundfish, including Atlantic cod (Bowen 1990, ICES 2005). Offshore renewable construction and ongoing operation could influence Grey Seal feeding. Grey Seals exposed to pile driving noise off the coast of the Netherlands have shown changes in dive behaviour and possible avoidance behaviour (Aarts et al. 2018). These effects appear to be short term as seals returned to the same locations on later trips. Grey Seals have also been tracked swimming through operational wind farms with no indication of overt avoidance off both the UK and Danish coasts (Russell et al. 2016). Entanglement in commercial fishing nets causes bycatch mortality in most parts of the Grey Seals’ range (Woodley and Lavigne, 1991). Bycatch levels are approximately 300 per year in Swedish fisheries in the Baltic (ICES 2005). Estimated bycatch levels in the Western Channel and Celtic Sea exceed the potential biological removal level for the combined Grey Seal populations of SW England, Wales, and Ireland. An additional but unknown number of seals are bycaught by non-UK registered boats operating in the Celtic Sea. Despite the bycatch, Grey Seal populations in Wales and Ireland are increasing, suggesting that bycaught seals include animals that may have originated from larger Scottish breeding populations. Grey Seals are known carriers of the morbillivirus known as phocine distemper virus (PDV), in all populations (Ross et al. 1992, Duignan et al. 1995, Harkonen et al. 2006). However, they have suffered almost no mortality from the disease. Harkonen et al. (2006) report Grey Seal mortality of approximately 230 (equal to 1% of the harbour seal mortality) in the 1988 epizootic in Europe, and the death of 30 gray seal pups in the Baltic were attributed to PDV. Because Grey Seals haul out with harbour seals in the Wadden Sea and are known to travel more widely than the sedentary harbour seal, it is presumed that they had a role in the outbreak and spread of the 2002 epizootic of PDV in harbour seals.

As a coastal species, Grey Seals are exposed to and ingest industrial and agricultural pollutants through the food chain. PCBs and DDT contaminant loads are extremely high in Baltic Sea Grey Seals, even though tissue burdens have declined since the 1970s. Analysis of samples collected from 1996 to 1998 indicated that gray seals still have a very heavy load of contaminants when compared to other seals outside the Baltic (ICES 2005). Health effects on Grey Seals have been suggested to be linked to very high exposures of PCBs and DDT. Baltic Sea Grey Seals have a relatively high rate of colonic ulcers, sometimes fatal, associated with hookworm infestations. This condition occurs in the Baltic Sea ringed seals as well, but essentially not found elsewhere in either species (ICES 2005). Uterine stenosis and a range of pathologies in other organs have been attributed to long-term exposure to environmental toxins, particularly in older Baltic Sea gray seals. These are specifically linked to reproductive, and population declines for this subspecies, and are conditions not seen in other populations (Bergman et al. 2001). However, no negative effects have been attributed to heavy metal contaminants in the Baltic gray seals (Bergman et al. 2001, ICES 2005).

The potential effects of climate change, either warming or cooling, on Grey Seals are not well known. In the Western Atlantic subspecies, decreases in the amount of sea ice in the Gulf of St. Lawrence during the pupping season have led to a shift to land breeding and may have increased pup mortality (den Heyer et al. 2021). A shift in mean birthdate of almost two weeks at the Sable Island colony in the Western Atlantic has been associated with a warming trend and an increasing population (Bowen et al. 2020). None of the above is thought to be a major threat to the species at present.

Grey Seals have been important in subsistence harvests in coastal areas within their range throughout history. 

In Norway, hunting quotas are set within the context of a Grey Seal management plan and bounties have also been paid to reduce numbers in areas where there are conflicts with fisheries (Nilssen and Haug 2007). Licenced hunting also occurs in other Baltic countries (including Sweden and Finland). Commercial Hunting of Grey Seals is also permitted in Iceland was banned in 2019 (Hauksson 2007). The provision for killing of seals to protect fish farms was removed in the UK and Faroe Islands in recent years in line with the US Marine Mammal Protection Act Import Provision Rule. In the Faroe Islands, licenses to kill Grey Seals are issued for the purpose of protecting marine fish farming (Mikkelsen 2007).

Numerous countries have invoked protective measures to limit Grey Seal harvests, culls, disturbance, and by-catch (Bonner 1981, ICES 2005). In the UK, Grey Seals are protected under the Conservation of Seals Act 1970 (England, and Wales), the Marine (Scotland) Act 2010 and The Wildlife (Northern Ireland) Order 1985. Until recently permits to protect fishing and aquaculture operations from grey seals were required, however, the lethal removal of grey seals in defence of gear damage this provision has been removed from legislation (SCOS 2020). In the UK such shooting was already restricted (in numbers and/or location) and it was unlikely to have had impacts on population trends.

Special Areas of Conservation (SAC) set out under the European Union's Habitats Directive (92/43/EEC) have been established to support the conservation of grey seals throughout its range. Pollutant loads in Baltic grey seals have declined in step with regulations banning the use and/or discharge of toxic pollutants such as DDT and PCBs beginning in the 1970s, and the reproductive health of female Grey Seals has improved as has the population level in the Baltic (Bergman et al. 2001). The establishment of coastal marine reserves for seals in Norway has been more effective in protecting harbour seals than Grey Seals because the latter are more likely to travel outside the areas closed to fisheries and become entangled in nets (Bjore et al. 2002).