Phoque gris

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.

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).