Harbour Seal
(Phoca vitulina)
| Distribution and Numbers The harbour seal is the most widely-distributed pinniped, inhabiting temperate and subarctic coastal areas on both sides of the north Atlantic and north Pacific Oceans. Population estimates are imprecise or unavailable for most areas in the harbour seal's range. It is thought however that there may be a total world population of about 400,000-500,000 seals. There has been much debate in recent years regarding the classification of the species, but five separate subspecies are generally recognised at the present time. |
| The eastern Atlantic harbour seal (P.v. vitulina), also known as the common seal, has an estimated population size of 88,000-93,000. The subspecies is found in Svalbard, Iceland, the British Isles, the southwestern Baltic Sea, and on western European coasts from northern Norway to France, including the Kattegat and Skagerrak. A few individuals have been found wandering as far south as Portugal. The western Atlantic harbour seal (P.v. concolor) is found from the eastern Canadian Arctic and Greenland down to New Jersey, individuals occasionally wandering as far south as Florida. There is no reliable population estimate for the small Greenland population, but the American and Canadian populations are thought to total about 60,000-70,000 seals. |  P.v.vitulina Photo: Salko de Wolf, Ecomare |
| The eastern Pacific
harbour seal (P.v. richardsi) population consists
of an estimated 285,000 seals, distributed from the Pribilof and Aleutian Islands in
Alaska as far south as Baja California. The western
Pacific harbour seal (P.v. stejnegeri), also known
as the Kuril or insular seal, has an unknown abundance, perhaps less than 4,000 seals, and
ranges from the western Aleutian and Commander Islands south to the Kuril Islands and
Hokkaido. The Ungava seal (P.v. mellonae), also known as the Lacs des Loups Marins harbour seal,
lives in freshwater lakes and rivers on the Ungava peninsula of northern Québec. The
number of Ungava seals is unknown but may be in the order of 100-600, probably towards the
lower end of this range. |
| Status Harbour seals in many areas remain in the vicinity of their traditional breeding sites all year round. This restricted range means that the viability of local harbour seal populations can be particularly at risk. A number of local populations have already disappeared, e.g. the Lake Ontario population which was exterminated by the early 1800s, or have had their numbers drastically reduced by human activity. The Greenland, Hokkaido and Baltic Sea populations in particular are currently under severe threat, while in the Gulf of Alaska there have been drastic population declines in some areas within the last 20-30 years. |
| Many of the fish species eaten by harbour seals are also commercially fished, the resulting interactions between the seals and commercial fisheries being a source of mortality. Harbour seals can become entangled and drown in fishing nets and gear, especially by gillnet fisheries in places like Alaska and the coasts of Canada and the United States. In several countries, such as Canada, Norway and the United Kingdom, it is legal to shoot harbour seals to protect fisheries or fish farms. Conservation groups are attempting to promote the development and use of humane non-lethal seal deterrence methods, including effective anti-predator nets on fish farms and the movement from open sea cage fish farms to land-based closed loop systems. An unknown level of illegal killing of harbour seals, mainly by fishing interests, also takes place throughout the species' range. |
 P.v.richardsi Photo: Phillip Colla, Phillip Colla Wildlife Photography |
Culls of harbour seals are regularly called for by those who believe that the seals are eating too much fish, despite evidence showing that the simplified view of "less seals equals more fish" is misguided given the complexity of the marine food web. Those opposing such culls say that the seals are being made scapegoats, and that overfishing, habitat alteration and marine pollution are the causes of dramatic decreases in fish stocks. Many seal populations are only just now recovering from bounty schemes and organised culling, most of which ended in the 1960s and 1970s. Local culls with the aim of protecting migrating fish still occur from time to time. While there is currently no commercial hunting of the harbour seal, such hunting greatly reduced populations throughout the species' range in the 19th and 20th centuries. Some native subsistence hunting of harbour seals still occurs. |
| There is great concern as to the effects on harbour seals of environmental contaminants such as organochlorines. It has been suggested, for example, that the effects of the 1988 epizootic affecting the eastern Atlantic harbour seal may have been worsened by impairment of the harbour seals' immune systems by pollutants. There is some evidence that lowered productivity and premature parturition in harbour seals are related to pollutants, as seen in Europe and San Francisco Bay in the United States. The risk to harbour seals from oil and hydrocarbon contamination is also significant. Physical debris is an additional threat to harbour seals, individuals being killed throughout the species' range by entanglement in marine debris, particularly non-biodegradable fishing nets and plastic wrapping bands. Harbour seals have also been killed by being trapped in the intake pipes of power plants in the United States. |
| The transmission of disease from humans to pinnipeds and pinnipeds to humans is an area of increasing interest. Brucellosis has been documented in harbour seals in both California and Washington State. A new virus that was similar to a bovine pneumonia was also reported in harbour seals in Point Reyes, California, when over 100 seals died suddenly over a three month period in 1997. |
| Human disturbance has been known to cause problems to harbour seal populations, particularly because of the tendency of the species to inhabit coastal areas where activities such as vessel traffic, construction and leisure pursuits are common and increasing. Disturbance during the pupping season can cause the deaths of some pups due to separation or abandonment, while haulouts experiencing a high level of disturbance may be abandoned completely. |
| Eastern Atlantic harbour seal: In 1988 an epizootic of phocine distemper virus (PDV), a morbillivirus closely related to canine distemper virus, swept through harbour seal populations from the Kattegat to the North Sea, through the Wadden Sea, killing over 18,000 eastern Atlantic harbour seals. Most of the seals died from secondary infections, particularly bacterial pneumonia. The origin of the epizootic is still unclear but one popular theory is that the virus was transmitted to harbour seals from harp seals. Most populations appear now to have recovered from the virus. |
| Fishermen and fish farmers in the United Kingdom do not need to report the shooting of seals under the "Fisheries Defence Clause" of the Conservation of Seals Act and therefore the scale of such killing in the U.K. is uncertain. Official statistics show that more than 60 harbour and grey seals (Halichoerus grypus) were legally shot under licence by Scottish fishery boards during the year 2000, the most in more than a decade. Conservationists however say that the official figures hide the fact that a very large number of both species, estimated by some organisations as totalling several thousand seals, are shot under the Fisheries Defence Clause each year in Scotland. |
| Hunting of harbour seals still takes place in Iceland and Norway. The harbour seal population in the Baltic Sea was severely depleted in the 20th century by hunting, pollution and the PDV virus. A 1998 survey revealed that there were only 580 harbour seals left in the Baltic Sea, with no detectable increase in the population size since 1994. The eastern Atlantic harbour seal is listed as an Appendix III species under the Bern Convention, and the subpopulations in the Baltic and Wadden Seas are listed as an Appendix II species under the Bonn Convention. The species is also listed as a protected species under Annex II and Annex V of the European Community's Habitats Directive, and several important sites for the harbour seal have been proposed in EC member countries as Special Areas of Conservation under the Directive. |
| Western Atlantic harbour seal: Fisheries and aquaculture-related mortality of the subspecies is high. An estimated average total of 873 seals were killed each year by fisheries in the United States between 1994 and 1998, mostly by entanglement in nets of the Northeast multispecies sink gillnet fishery in the Gulf of Maine and southern New England. A number of seals are also killed by deliberate shooting and by increasing interactions with aquaculture in the United States but the level of this mortality is currently unknown. In Canada seals are entangled in nets of groundfish gillnet fisheries in Newfoundland and Labrador, the Gulf of St. Lawrence and the Bay of Fundy, and also in nets of the Atlantic Canada salmon gillnet fishery. A number of seals have also been entangled in nets of the Spanish deep water trawl fishery off Canada. The overall numbers of seals entangled decreased after the Greenland salmon gillnet and Atlantic Canada cod trap fisheries were ended in 1993. An unknown number of seals are shot at herring weirs in the Bay of Fundy and the Canadian government has implemented a pilot programme to allow aquaculture installations to shoot seals. Inuit natives also kill small numbers of seals in Canada. |
| The population in Greenland is vulnerable to hunting and disturbance, the harbour seal disappearing there in recent years from some of its former sites, and its numbers declining even in several protected areas. The harbour seal is prized by locals in Greenland for its meat and its fine silky hair, the harbour seal skin being part of the Greenlandic national costume. It is thought that about 40 seals are hunted in Greenland each year, but this figure may be understated. |
| At least 445 harbour seals, mostly juveniles, died of acute pneumonia due to an Influenza A virus of avian origin that lasted 22 months in New England from 1979-80. A less severe outbreak killed 60 seals in 1982. Other sources of mortality of the subspecies include boat strikes, drowning in power plant intake pipes (an estimated 12-20 each year in the United States) and oil pollution. The eastern and Arctic populations of the Western Atlantic harbour seal were added to Canada's Species at Risk list for 1999 with the the status Indeterminate. |
| The first few months of 2001 saw reports of a large increase in sightings of various seal species, including harbour seals, along the eastern seaboard of the United States, as well as an increase in the number of seals needing rescue and rehabilitation. The cause is as yet unknown but some of the reasons being suggested include larger seal populations due to cleaner habitat and/or reduced hunting, increased commercial fishing in northern waters forcing seals further south to look for food, weather conditions and greater public awareness. Many of the seals requiring assistance were undernourished pups, while others were adults that had been injured, bitten by other seals or weakened by parasites or bacterial infections. |
| Eastern Pacific harbour seal: There has been a significant decline in the harbour seal population in the Gulf of Alaska and the Aleutian Islands since the 1970s, particularly in some areas such as Tugidak Island, which has seen a decrease in population size of 90%, and Prince William Sound. The cause for this decline is unknown but may be linked to similar drops in Steller sea lion and Northern fur seal numbers in the region. The population in the Bering Sea is thought to be declining, the populations from California to Washington are either stable or increasing slightly, and it is thought that the population in British Columbia may now be approaching its carrying capacity. |
| Harbour seals in the southern parts of the range can be adversely affected by the lack of food produced by El Niño events. The population at Point Reyes, California, for example, reproduced at around half the level of the previous year during the 1997-98 event, and at a reduced level during the 1982, 1986 and 1992 events. The vast majority of fisheries-related mortality in California is caused by entanglement in gillnet fisheries although the extent of this problem is currently unknown. This source of mortality has however declined recently due to a reduction and redistribution of fishing effort. |
| The kill of harbour seals by Alaskan native subsistence hunting in 1996 was estimated at 2,741 and is fairly constant from year to year. Several Northwest Indian tribes have developed or are developing regulations for the ceremonial and subsistence killing of harbour seals, one tribe having reportedly made plans for a commercial hunt of the species. A minimum estimate of 103 harbour seals are killed each year by entanglement in Alaskan fisheries, particularly gillnet fisheries, but this estimate is unreliable and the figure could be much higher. |
| The U.S. federal National Marine Fisheries Service released a report in 1999 recommending that Congress allow, in the next reauthorisation of the Marine Mammal Protection Act, state and federal wildlife managers to kill harbour seals that are preying on endangered fish species in Washington, Oregon and California. The report also recommended that authority be given to kill seals which pose a threat to public safety and property at locations such as docks and marinas, and that commercial fishermen be allowed to kill seals that destroy their catch or gear. Permission for fishermen to kill seals in this way was previously withdrawn in 1994. The report has been roundly condemned by animal welfare and conservation groups who argue that effective and humane non-lethal deterrence methods should be developed and that the problem of overfishing should be addressed. |  P.v.richardsi Photo: Phillip Colla, Phillip Colla Wildlife Photography |
| In Canada a total of 31 harbour seals were killed in the Puntledge River, Vancouver, in 1997 with the aim of protecting migrating fish. It has also been revealed that 470 harbour seals were killed legally under predator control permits by the British Columbia fish farming industry in 1999, mostly in the Vancouver Island area. In 1989 the oil spill from the tanker Exxon Valdez in Prince William Sound, Alaska, affected some of the largest harbour seal haulout sites in the area. It is thought that about a third of the harbour seals using oiled haulout sites were killed, and that pup production and survival were also affected. Not only did the seals become coated with oil and inhale volatile substances, but the oil was also incorporated in seal tissues, abnormal behaviour was experienced, and pathological brain damage occurred. |
| In 1997, around 90 dead harbour seals stranded on the Californian coast, the cause of which was inconclusive but appeared to be a virus of some type. A similar but smaller mortality of 25 dead adult harbour seals was reported from Point Reyes, California, in June 2000. There is also concern that the seals of San Francisco Bay may be experiencing reduced productivity because of elevated PCB levels. Additional mortality of the subspecies occurs from being trapped in the intake pipes of power plants, being struck by boats and deliberate shooting. |
| In March 2001 the California Coastal Commission approved an application by the San Diego City Council to renew the 0.4 hectare Seal Rock Marine Mammal Reserve in La Jolla for another five years. The Reserve was originally established in 1994 in order to protect the area's harbour seals from harassment and disturbance. The species' habitat in California was afforded additional protection when the California Coastal National Monument was created in 2000, providing federal protection to thousands of islands, rocks, exposed reefs and pinnacles up to 19km offshore along the California coast. |
| The harbour seal population in Mexico, about 1,000 to 3,000 individuals, is fully protected under the Ley General de Vida Silvestre NOM-059-ECOL-1994 which forbids the killing, collecting or possession of the species or any part or product obtained from the species. Despite this protection harbour seals have been known to have been killed as bait for shark long line fishing in Baja California. They are also sometimes found entangled in gillnets. The Biosphere Reserve of El Vizcaino in Baja California Sur provides a large proportion of the rocky haul out habitat for harbour seals. |
| Western Pacific harbour seal: Due to entanglement in fishing nets, particularly salmon trap nets, the threatened population in Hokkaido, which only has an estimated 300-400 seals, is experiencing an annual level of mortality that exceeds the number of seals being born into the population. Pollution of the area is also a problem and the number of pinnipeds found stranded in Japan has recently increased. Some native subsistence hunting of harbour seals takes place in Russia. |
| Ungava Seal: The
Ungava seal has been assigned the status Vulnerable by the Committee on the Status of Endangered Wildlife in Canada, which describes
it as a "unique endemic subspecies of harbour seals with limited range and low
numbers, making it vulnerable to human impact and natural catastrophic events". It is
thought that a proposed hydroelectric development may have an adverse impact on a large
portion of the population's range by reducing the water level of the Lac des Loups Marins.
The population currently has minimum legal protection in Canada and none of its habitat is
protected. However the Québec government is considering whether or not to give legal
protection to a portion of the habitat. There is some occasional hunting of the seals by
the local native peoples for subsistence purposes. The Ungava seal is listed as Data deficient on the IUCN
Red List. |
| Lifestyle There is much variation in the appearance, physiology and behaviour of the harbour seal throughout its wide range. Generally the species is gregarious, hauling out in small scattered groups to breed, moult and rest, although some colonies in protected bays and estuaries can number over 1,000 individuals. Many different types of habitat are used for hauling out, including rocky shores, reefs, skerries, sand and gravel beaches, intertidal mud and sand bars, piers, and, in some places, drifting glacial ice. In general the species seems to prefer protected rather than exposed areas. Suitable characteristics for a haulout site seem to include adequate protection from land predators, direct access to deep water, proximity to food resources, and protection from strong wind and waves. It is thought that the necessity to avoid predators is one of the main reasons that harbour seals prefer to haul out in groups rather than alone. |
 P.v.richardsi Photo: Phillip Colla, Phillip Colla Wildlife Photography |
The species' haulout patterns tend to be strongly influenced by tidal cycles and many seals haul out on the falling tide in areas below the high tide mark. When tidal influences are removed however, time of day is the major influence on harbour seal haulout behaviour. Lesser numbers of harbour seals are generally seen hauled out in autumn and winter than in spring and summer. A study in Alaska for example showed that seals in Prince William Sound spent approximately 70% of their time in the water from September-April, declining to 60% in May and 40% in July. Individuals of the species tend to stay in the same area all year round, although there are many seals, particularly juveniles, that are known to travel long distances, sometimes up to 500km, to feed. Juveniles tend to travel longer distances than adults to feed and tend also to have larger home ranges. |
| More localised movements in search of food, or perhaps to follow migrating fish, are common. Harbour seals tend to stay within 25km of the shore but individuals are occasionally found 100km or more offshore. Some seals seasonally visit or inhabit freshwater streams and lakes, while the distribution range of many populations seems to be extended during the autumn. |
| Pupping seasons vary for different populations (see below). Most pups are born with their adult coat, having shed a grey-white woolly coat before birth. Some pups however, especially the pups of younger mothers, are born with this pre-natal coat and moult it shortly afterwards. Harbour seal pups are precocious and are almost immediately able to crawl and swim, often within an hour of birth. This adaptation is essential for those pups born in intertidal areas. Pups weigh an average of 13-14% of their mother's body weight at birth, large compared to other phocid seals at 8-10%. Nursing of the pup, mostly on land but also in water, usually takes about 4 weeks. The pup puts on weight at the rate of around 0.5-0.7kg per day. During this time the mother makes short feeding trips, the duration of which become longer through the nursing period. Weaning of the pup can either be abrupt or gradual, both mother and pup becoming less interested in each other towards the end of the nursing period. After being weaned the pups tend to disperse from their birth site, often travelling long distances to explore their new habitat. |
| Mating takes place around the time of weaning and, for the most part, in the water. Very little is known about the mating habits of harbour seals, although recent studies indicate that the adult males gather in an area where females may be attracted to mate. During this period the males perform aquatic displays and underwater vocalisations that may be related to competition with other males or may serve to attract females. Some researchers believe that the males maintain underwater territories. Many fights between males take place and neck wounds are commonly seen during this period. Males lose up to 25% of their body weight during the breeding season from the energetic requirements of competing and breeding. |
| The pattern of harbour seal coats varies widely. The background colour, often brown, tan or grey, ranges from dark to light in different seals and is covered with light or dark rings, spots and blotches. The pattern on a harbour seal's coat is unique to each seal and does not change from year to year, a useful feature in the identification of individuals. A red to orange coloration is also found in a number of seals, especially in San Francisco Bay which has the highest incidence of red fur in the world, 40% of the seals on average compared to <1% at most other locations. The red coloration is caused by the attachment of iron oxides to the external hair shaft. The cause for this deposition is currently unknown but may be related to genetics, foraging strategies, pollutants, or a combination of these factors. |
| The time of year (see below) and duration of the moult vary between populations, also varying within each population for individuals of differing age, sex and reproductive status. Seals haul out a lot during the moult, averaging 12 hours per day hauled out compared to 7 hours per day during the non-moult season, probably because warm skin enhances the growth of new hair. The metabolism of harbour seals also reduces while they are moulting, meaning that the seals do not need to spend as much time catching food during the moult than at other times of the year. |
| Harbour seals are opportunistic foragers, feeding on locally and seasonally abundant prey that includes a large number of species of fish, crustaceans and molluscs. Feeding is usually carried out near the shore in water depths less than 200m, individuals diving to fairly shallow depths, usually less than 100m, for short periods of a few minutes. The species is preyed upon in many parts of its range by killer whales and sharks. Polar bears are known to be predators of Western Atlantic harbour seals. Pups may also be preyed on by coyotes, foxes and large birds of prey, while harbour seals in the Pacific are known to be killed by Steller sea lions. It was reported in 2000 that two adolescent male sea otters had been seen sexually assaulting and drowning harbour seal pups in Monterey Bay, California, but this behaviour is thought to be extremely unusual. |
| Ungava Seal: The vast majority of the lakes and rivers in the subspecies' range are covered by ice at the time of pupping. It is thought that the seals may winter in the larger lakes and then disperse into the smaller rivers and lakes when the ice melts. Ungava seals haul out in small groups in spring but alone or in pairs at the end of summer. The subspecies feeds exclusively in freshwater and is the only known harbour seal population resident in freshwater all year round. The diet of Ungava seals has not been well studied, but they are known to prey on salmonids such as small brook trout. |
Pupping and Moulting seasons:
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| Statistics Alaskan and western Pacific harbour seals are significantly larger than those in the Atlantic and those in the more southern areas of the eastern Pacific. Hokkaido seals appear to be the largest with an average length of 1.9m for adult males and 1.7m for adult females. Generally however adult males measure 1.4-1.9m in length and weigh 55-170kg, while the smaller adult females measure 1.2-1.7m in length and weigh 45-105kg. Pups are usually born measuring 70-100cm in length and weighing 8-12kg. Most male harbour seals reach sexual maturity at 5-6 years of age, females earlier at 2-5 years. Harbour seals have sometimes been known to dive over 500m and for periods over 25 minutes. Male harbour seals have a shorter lifespan than females, possibly due to the stress of competing and fighting during the breeding season. Males can live up to around 20 years of age, females to around 25-30 years. |
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