Harbour Seal

Updated: May 2020

The harbour seal is a small phocid seal (“true seal”). They average around 150 cm in length and 70-100 kg in weight, and the males are generally larger than the females. Their coat colour pattern is very variable, but is usually silvery and darker on the back, creamy or lighter-grey on the belly and flanks, with dark spots covering the entire body. Pups can occasionally carry a fluffy white coat at birth, but this is usually shed in the uterus. This means that most of the time, pups are born in their adult-pattern coat (Bjørge et al. 2010).

Harbour seals are generalist predators, but prefer small to medium-sized fish. They are a coastal species that can be found hauling out in groups of up to several hundred animals.

Harbour seal populations in the North Atlantic identified by genetics (Andersen and Olsen 2010, Andersen et al 2011).

ABUNDANCE

There are estimated to be approximately 200,000 harbour seals in the North Atlantic.

DISTRIBUTION

They inhabit temperate to sub-Arctic waters along the eastern and western coasts of the North Atlantic. Svalbard is home to the northernmost population of harbour seals.

RELATION TO HUMANS

Harbour seals are hunted in Norway and Iceland for their meat and skin.

CONSERVATION AND MANAGEMENT

Scientific advice for the management of harbour seals in the North Atlantic is provided by NAMMCO. Management is the responsibility of each country.

In the most recent assessment (2016), the species is listed as being of ‘Least Concern’ on the European and global IUCN Red List, as well as on the Norwegian national red list. However, it is listed as ‘Vulnerable’ for Svalbard (Norway) and as ‘Critically Endangered’ on the Icelandic and Greenlandic national red lists.

© Sandra Granquist/Icelandic Seal Centre

© Wordless Symbol/Wikipedia

Scientific name: Phoca vitulina

Faroese: Steinkópur
Greenlandic: Qasigiaq
Icelandic: Landselur
Norwegian: Steinkobbe

Danish: Spættet sæl/Spraglet sæl
English: Harbour seal, common seal

Lifespan

Females: 30-35 years, Males: 20-25 years

Productivity

One pup per year

Feeding

Generalist predator, with an overall preference for small to medium sized fish including cod, herring, sandeel, and flatfish

Size

Around 150 cm in length and 70-100 kg in weight, with the males generally being larger than the females

© Wikipedia

General characteristics

The harbour seal (Phoca vitulina) is a coastal, non-migratory species. It can be found in the temperate and subarctic waters of the northern hemisphere. Four (marine) subspecies are recognised:

Eastern North Atlantic (P. v. vitulina; Linnaeus 1758) – distributed throughout Svalbard, Norway, Russia, Iceland, Denmark, Sweden, Germany, Poland, United Kingdom, Ireland, Netherlands, Belgium, France.

Western North Atlantic (P.v. concolor; DeKay 1842) – distributed from Labrador in Canada to Virginia in USA and in Greenland.

Eastern North Pacific (P. v.richardii; Gray 1864) – distributed throughout Alaska, some Russian islands, and the west coasts of Canada and the USA.

Western North Pacific (P.v. stejnegeri; Allen 1902) – distributed from eastern Siberia in Russia to northern Japan. This subspecies is also sometimes treated as a separate species, Phoca kurilensis or Phoca insularis (Bjørge et al. 2010).

Only the first two of these subspecies are found in the NAMMCO area.

There are, in addition, some landlocked harbour seals in lakes and connecting rivers in the Ungava Peninsula, Northern Quebec, Canada (Smith et al. 1996). These seals are recognized as a fifth (non-marine) sub-species: the Ungava seal P.v. mellonae (Doutt 1942).

Harbour seals are small phocid seals. They average around 150 cm in length and 70-100 kg in weight, and the males are generally larger than the females. The colour pattern of their coat is very variable, but usually silvery and darker on the back, creamy or lighter-grey on the belly and flanks, and with dark spots covering the entire body. Pups can occasionally carry a fluffy white coat (called lanugo) at birth, but this is usually shed in the uterus. This means that most of the time, pups are born in their adult-pattern coat (Bjørge et al. 2010).

Behaviour

harbour seals

© Icelandic Seal Centre

Harbour seals show strong site fidelity. They move between haul-out sites and feeding areas, but rarely show seasonal migration. These seals haul out, give birth and nurse their young on beaches, sandbanks and rocks, usually in the intertidal zone along the coast. They also forage in close proximity to the coast. They can dive deeper than 200 m, but perform on average much shallower dives (60-100 m), mainly as a consequence of their habitat choice (Sharples et al. 2012, Ramasco 2015). The occurrence of resting dives, similar to the typical drift dives performed by other phocid seals (Crocker et al. 1997), has also been documented in harbour seals (Ramasco et al. 2013).

Harbour seals are opportunistic feeders, however they are more benthic (bottom of the sea) than pelagic (in the water column) feeders. They use different underwater feeding techniques, depending on prey type, including ambush, active search or digging with final pursuit (Bowen et al. 2002). They are highly social animals. Although they mostly feed independently, they gather to rest at haul out sites on a regular basis, usually timed with low tide in areas where the tidal cycle strongly impacts the geography of their habitat (Cronin et al. 2009).

Life History and Ecology

The annual reproductive cycle of most seal species is characterized by a tight synchrony of births, ensuring that pups are born at the optimal time of year (Boyd 1991). Across their range, harbour seals give birth to one pup per year between February and July, depending on the environmental conditions and population status, with lower latitudes and populations in good conditions breeding earlier (Reijnders, Brasseur and Meesters 2010). Lactation lasts about three to four weeks, but the pup is able to swim already just a few minutes after birth. Male harbour seals come into breeding areas towards the end of the lactation time and perform underwater displays to attract females to mate (Van Parijs et al. 1997). Although harbour seals mate during this period, the females have delayed implantation. Harbour seal pregnancies last around eight months.

© Nevit Dilmen/Wikimedia

Harbour seals are known to be generalist predators, with an overall preference for small to medium sized fish (Ramasco 2015). They commonly feed on codfish (Gadidae), sandeel (Ammodytes sp.), herring (Clupea harengus) and flatfish (Pleuronectidae) depending on their surrounding habitat (Härkönen 1987, Olsen and Bjørge 1995, Bowen and Harrison 1996, Tollit et al. 1998). Differences in their diet (with seasonal and interannual variability) are documented across their geographical range (Härkönen 1987, Pierce et al. 1991, Hall et al. 1998). The shifts in diet over time are often linked to changes in the most abundant prey species to be found in their preferred size group (Ramasco 2017). Harbour seals have been observed to respond to different prey pulses, such as seasonal increased concentration of herring or salmon (Middlemas et al. 2006, Thomas et al. 2011).

Distribution and Habitat

Harbour seals are distributed across temperate to sub-Arctic waters along the eastern and western coasts of the North Atlantic and the North Pacific Oceans (Bjørge et al. 2010). They primarily use areas close to the coastline, i.e. within 50 km (Jones et al. 2015), and generally do not perform seasonal migrations. In certain areas, for example where ice cover limits food or habitat accessibility during part of the year, the species shows small-scale seasonal migrations (Lesage et al. 2004).

Although the species was extirpated from the Faroe islands over 100 years ago, rare observations do still occur. In 2019, a harbour seal was observed in Tórshavn for a period of a few weeks in August (National Progress Report 2019).

harbour seals
© Icelandic Seal Centre

North Atlantic stocks

Andersen and Olsen (2010) reviewed genetic studies done on harbour seal populations in the North Atlantic and identified twelve distinct populations: USA/Canada, Iceland, west coast of Norway, Ireland-Scotland, English east coast, Channel area, Wadden Sea, Limfjord, Skagerrak, Kattegat, West Baltic, and East Baltic/Baltic proper.

A subsequent study compared the Greenland and Svalbard populations to those that were geographically closest – mainland Norway and Iceland – and found them to be distinct (Andersen et al. 2011). Most of the genetic studies reviewed do not investigate potential population differences within each country, suggesting that the number of genetically distinct harbour seal populations is likely higher than 14. Two subsamples from Iceland that were analysed by Andersen et al. (2011) did not show significant differentiation though.

Current management units for Norwegian harbour seals are defined by county limits. However, information on the movement patterns of harbour seals in Norway (Bjørge et al. 2002b, Ramasco 2015) as well as recent genetic evidence of fine scale population structure in Danish and Swedish waters (Olsen et al. 2014), raises concerns that there may be population subdivisions within counties. Since some counties are quite large (with long coastlines), the management units are likely larger than the biologically significant populations.

Harbour seal populations in the North Atlantic identified by genetics (Andersen and Olsen 2010, Andersen et al 2011).

Current Abundance and Trends

An estimate of the world population of harbour seals put them at approximately 610,000 – 640,000 individuals, including both the Atlantic and Pacific stocks (Bjørge et al. 2010). In 2016, the NAMMCO Scientific Committee endorsed the following table with abundance estimates from the Coastal Seals Working Group (NAMMCO 2016). A new meeting of the working group will take place in 2020 and it is expected that new information will be available following that meeting.

Summary of abundance estimates and trends for harbour seals in the North Atlantic (NAMMCO 2016)

Stock Status

The NAMMCO Council has previously requested an assessment of the species in the North Atlantic. As a result, the Scientific Committee convened a Working Group to review the status of harbour seals throughout the North Atlantic, which resulted in Volume 8 of the NAMMCO Scientific Publications series being published in 2010 with a focus on harbour seals in the North Atlantic and Baltic. The working group met again in 2016 and noted that harbour seals appear to be declining in many areas (especially where grey seals are increasing), although there are little data to indicate if grey seals could have an impact on the harbour seal populations.

Greenland

The total number of harbour seals in Greenland was estimated at about 3,000 in 1950 and fewer than 1,000 in 2007. To this date, there are only around 100 seals in the three-known breeding/molting localities, although observations of harbour seals far from these areas indicate that there may be some additional small breeding and molting sites not yet detected. Current research aims to monitor the known sites and to locate the suspected additional sites (Research in NAMMCO Member Countries). The number of harbour seals in the southernmost part of Greenland has increased significantly in recent years, while historically used haul-out locations along the west coast have gradually been abandoned after the 1950s (Rosing-Asvid 2010). All hunting on this species was banned in 2010 and it is believed that several small remnant populations still exist, but live undetected.

Iceland

The Icelandic harbour seal population was considerably larger in the early 19th century than at present, with about 60,000 (90% CI = 40 – 100) animals. Aerial surveys conducted since 1980 indicate that the population has declined from 33,000 (90% CI = 26,000 – 44,000) animals in 1980 to about 12,000 (90% CI = 9,000 – 16,000) animals in 2006. Since 2003, total removals have decreased and the population decline appears to have ceased (Hauksson and Einarsson 2010). During the latest full census in 2016, the population was estimated to be about 7,700 animals (Þorbjörnsson et al. 2017), which is a decrease of 30% since 2011. The reasons for the decline are not known, but could include hunting, changes in prey species, by-catch (seals caught in fishing nets), ecosystem changes related to climate change, and disturbance from tourism. These issues are currently being investigated by researchers at the Marine and Freshwater Institute in Iceland, and the Icelandic Seal Center.

Faroe Islands

The harbour seal was exterminated as a breeding species in the Faroe Islands in the mid-19th Century. For the last 40 years the harbour seal has only been positively identified twice in the Faroe Islands, in 2001 and 2005 (Mikkelsen 2010).

Norway

Harbour seals in Norway suffered a severe decline prior to the 1960s due to unregulated hunting (Øynes 1964). Regulatory measurements were introduced in 1973 in part of the country. A new management regime was implemented in 1997 with the aim to secure viable stocks. The most recent survey period (2011-2015) revealed a minimum total population of 7,642 harbour seals along the mainland Norwegian coast. This last estimate is close to the counts of 6,938 animals in 2003-2006 and 7,465 in 1996-1999, revealing a stable population trend since the 1990s (NAMMCO 2016).

A distinct population of around 1000 individuals is to be found in Svalbard (Lydersen and Kovacs 2010).

Southern Scandinavia (Kattegat, Skagerrak, Western Baltic, Limfjord)

The harbour seal population in Southern Scandinavia has experienced repeated declines caused by hunting and epizootics. Harbour seals have disappeared from haulout areas along the Danish shores of Kattegat and in the westernmost part of the Baltic Sea, where they were previously numerous. In the 1920-30s, when abundance was at its lowest, the population is estimated to have been only a fraction of its original size. Following 30 years of protection, the population is currently approaching historic abundance and seems to have reached the carrying capacity in some areas, showing a decrease in population growth rates, possibly caused by density dependent effects (Olsen et al. 2010).

East Baltic

The small population of harbour seals in the east Baltic (also called Baltic proper) was hunted close to extinction in the beginning of the 20th century and experienced a severe bottle-neck minimum numbers in the 1970s. Protective measures (in the form of a hunting ban and the establishment of protected areas) have improved the situation and the hauled-out moulting population size in 2008 was 588. Despite the conservation measures, however, the population in the east Baltic is not expected to reach favourable conservation status within the foreseeable future (Härkönen and Isakson 2010).

Mainland Europe (Wadden Sea)

The Wadden Sea harbour seal population has been severely depleted by hunting in the first half of the 20th century. After hunting was stopped in the mid-1970s, the population recovered gradually. This recovery was twice interrupted by PDV outbreaks in 1988 and 2002 (see below for further information). These epizootics reduced the population by 57% and 50% respectively. They also lead to changes in age and sex structure of the population, which gradually returned to stability (Reijnders, Brasseur, Tougaard, et al. 2010). After the outbreaks, the population showed a strong recovery with a growth rate close to the considered the maximum possible for this species, with a constant increase until 2013. Recent growth rates show that the overall increase of the population has slowed down, possibly suggesting it has reached carrying capacity (NAMMCO 2016).

United Kingdom

The UK holds approximately 40% of the European harbour seal population, with the majority found around the coasts of Scotland (Thompson et al. 2010). A survey in 2011 counted 28,161 individuals in Great Britain, and 948 in Northern Ireland, for a total of 29,109 (NAMMCO 2016). A general decline has been observed in most harbour seal colonies around Scotland. The widespread declines, ranging from Shetland to the Wash, suggest that the causes, still unknown, may have been present over a large part of the North Sea and waters off western Scotland (Thompson et al. 2010). The populations in west Scotland and along the north, northwest and east coast of England appeared to have stable population numbers (NAMMCO 2016).

Atlantic Canada

A bounty harvest, as well as subsistence and commercial hunting, lead to a decline in the population from 1949 to the early 1970s. The bounty was removed in 1976 and harbour seals have been protected in the southern parts of their range since then. At that time, the total population south of Labrador was estimated to be 12,700 (Boulva and McClaren 1979). Since then, research has been limited to specific areas and there is little information available on total abundance and trends. For example, after increasing during the 1980s, harbour seal abundance on Sable Island underwent a rapid decline through the 1990s when it was estimated to be less than 100 animals (Bowen et al. 2003). In contrast, harbour seals are reported to have increased in the Bay of Fundy although the numbers are not known. There is some evidence suggesting that local abundance of seals at some known haulout sites in the more southern portions of Newfoundland and Labrador may have increased while abundance at sites in more northern areas of the west, northeast and Labrador coast are generally consistent with reports from the 1970s (Sjare et al. 2005). It has also been suggested that urban development resulting in habitat degradation is probably the most important factor affecting harbour seal populations in Atlantic Canada (Hammill et al. 2010).

Atlantic United States

The harbour seal is the most abundant and widespread seal species in this area. The number of harbour seals observed during the pupping season in this region has increased from about 10,500 animals in 1981 to 38,000 animals in 2001 (uncorrected counts, Waring et al. 2010). The corrected estimate of harbour seal abundance in 2001 was of 99,340 animals (CV=0.09) (Gilbert et al. 2005), this was higher than the most recent one in 2012, which was of 75,834 animals (CV=0.15, Waring et al. 2015a), indicating a slight decrease. Currently there is some uncertainty in the patterns of harbour seal abundance and distribution in the northeastern US. Johnston et al. (2015) document a decline in stranding and by-catch rates of harbour seals, providing support for an apparent decline in abundance.

Phocine Distemper Virus and fluctuations in abundance

Harbour seal abundances have fluctuated widely in the Northeast Atlantic in recent decades, mainly due to local outbreaks of the Phocine Distemper Virus (PDV). A first epidemic in 1988 killed about 50% of the harbour seals in Skagerrak-Kattegat, the Wadden Sea and the Wash in the UK, with the subsequent very rapid recovery of about 13% increase per year, and even higher growth rates observed regionally (Härkönen et al. 2006, Reijnders et al. 2010, Olsen et al. 2010). A new PDV epizootic struck the same populations in 2002 with mortality similar to (or in some areas less than) in 1988. A number of animals that gained immunity during the first epizootic may still have been part of the population in 2002 and thus contributed to there being less mortality.

In contrast to most other areas affected by the 2002 epizootic, the population in the Wash (UK) has continued to decline since the outbreak. A decline in harbour seal abundance since the late 1990s is also observed in Orkney, Shetland, and, to a lesser extent, in the Outer Hebrides and east Scotland. The abundance in west Scotland has, however, continued to increase (Thompson et al. 2010).

Other sources of mortality

Among the major sources of mortality are by-catch, predation by killer whales (Orcinus orca), competition, and viral outbreaks. The impact of predation by killer whales is unknown. In Norway, during winter, killer whales follow the over-wintering herring and may move closer to seal colonies and have been reported to eat harbour and grey seals. In Scotland, killer whale predation on harbour seals seems to be on the increase. Grey seals may also be a source of mortality for harbour seals, either as predators or as competitors. In various areas where harbour seals and grey seals overlap, the population growth rate of harbour seals is usually lower. This has been seen in the Baltic Sea, Sable Island (Canada), Scotland, and New England (US) (NAMMCO 2016).

Management

Norway

The hunt in Norway has been regulated by quotas since 1997 and in 2003, the quotas and bounties were increased. After a decade with high quotas and a declining population of harbour seals, a management plan for harbour seals was implemented in 2010. There have been decreases in the yearly reported catches since 2011 when quotas began to be based on scientific advice.

Management units for Norwegian harbour seals are defined by county limits. However, there are concerns that there may be population subdivisions within counties. Harbour seals are regularly counted along the entire Norwegian coast at known haulout sites during the moulting period from mid-August to early September. The government has decided that the harbour seal population should be stabilized at a level where 7,000 moulting seals can be recorded. A balance between the preservation of large seal populations and reduced damage on fisheries and aquaculture in the coastal zone is desired.

Iceland

In Iceland, seal hunting does not require a specific hunting license (only the license to own a weapon) and no specific quota system has been established for the seal populations. Seal hunting from land and shallow waters is managed by land owners and there are no special protected areas or protected periods (e.g., breeding season) of the year for seals except those imposed by land owners and general regulations on hunting. It is not mandatory to report direct seal catches to the government, however. reporting on by-catch is requried. Members of the Seal Farmers Union (SFU) can voluntarily report their catch statistics to the organization and other known hunters are contacted directly by the Icelandic Seal Center.

In 2006, the Icelandic government published a management plan where a minimum population size of 12,000 harbour seals was recommended (NAMMCO 2006). This recommendation has not been based on a biological assessment (NAMMCO 2016). The management plan states that management actions should be initiated if the population drops appreciably below that number, but no specific population regulating method has been mentioned.

United Kingdom

Under the Conservation of Seals Act 1970, the UK Natural Environment Research Council (NERC) has a duty to provide scientific advice to the government on matters related to the management of seal populations. NERC has appointed a Special Committee on Seals (SCOS) to formulate this advice. Formal advice is given annually based on the latest scientific information provided to SCOS by the Sea Mammal Research Unit (SCOS 2004).

Harbour seals are regularly monitored through aerial surveys of animals hauled out during the annual moult in early August. The Scottish and English east coast populations mainly haul out in tidal estuaries and are surveyed annually, using fixed wing aircraft and digital photography. Populations in north and west Scotland often haul out on rocky shores and are surveyed less frequently, using helicopters fitted with thermal imagers (Thompson et al. 2010).

Canada

The department of Fisheries and Oceans Canada has published an Integrated Fisheries Management Plan for Atlantic Seals for the period 2011-2015 (see Grey seals). In this plan, hunting is regulated for most of the Atlantic seals in Canadian waters. Commercial harvesting for harbour seals is not permitted under this management plan.

Hunting and Utilisation

Despite their widespread presence, harbour seals are currently only hunted in Norway, Iceland and Atlantic Canada.

Norway

In Norway, hunting of harbour seals is a regulated recreational hunt. Ideally, seals are shot when they are hauled out. If seals are shot in the water, they need to be retrieved or they will otherwise sink and be lost. Hence, this hunt often occurs in shallow waters or with the use of a small vessel as support. The use of rifles with expanding bullets is mandatory.

Iceland

Seal hunting in Iceland is focused almost entirely on seal pups, mainly for the skin; but the meat, the blubber (fat) and the flippers have played an important role for human consumption in the past. Pups are taken when they are a few weeks old, just towards the end of lactation. Net hunting around the river mouths is the most common method of hunting harbour seal pups. The hunting takes place in the spring. Annual takes range from 200 – 400 harbour seal pups. Harvests have declined in recent years because of the low market price of the skins. For a very long time before 1980, the catch was 4000 – 6000 harbour seal pups.

Greenland and Canada

In Greenland, all hunting of this species was officially banned in 2010.

In Nunavut (Atlantic Canada) harbour seals are hunted by Inuk people. There are currently no restrictions on the seasons or numbers of seals that can be harvested (Report of the Committee on Hunting Methods 2016).

 

Reported catches in NAMMCO member countries

CountryYearAreaCatch TotalQuota
Greenland2018East00
Greenland2018West00
Greenland2018Total00
Greenland2017East00
Greenland2017West00
Greenland2017Total00
Greenland2016East10
Greenland2016West30
Greenland2016Total40
Greenland2015East00
Greenland2015West30
Greenland2015Total30
Greenland2014East10
Greenland2014West190
Greenland2014Total200
Greenland2013East00
Greenland2013West100
Greenland2013Total100
Greenland2012East00
Greenland2012West00
Greenland2012Total00
Greenland2011East100
Greenland2011West690
Greenland2011Total79*0
Greenland2010Total26*0
Greenland2009Total33No quota
Greenland2008Total81No quota
Greenland2007Total86**No quota
Greenland2006Total77**No quota
Greenland2005Total**No quota
Greenland2004Total**No quota
Greenland2003Total**No quota
Greenland2002Total**No quota
Greenland2001Total73No quota
Greenland2000Total124No quota
Greenland1999Total148No quota
Greenland1998Total217No quota
Greenland1997Total295No quota
Greenland1996Total255No quota
Greenland1995Total266No quota
Greenland1994Total278No quota
Iceland2019Iceland13
Iceland2018Iceland43
Iceland2017Iceland50
Iceland2016Iceland148
Iceland2015Iceland159
Iceland2014Iceland203
Iceland2013Iceland306
Iceland2012Iceland105
Iceland2011Iceland68
Iceland2010Iceland67
Iceland2009Iceland57
Iceland2008Iceland34
Iceland2007Iceland72
Iceland2006Iceland100
Iceland2005Iceland121
Iceland2004Iceland146
Iceland2003Iceland416
Iceland2002Iceland371
Iceland2001Iceland611
Iceland2000Iceland656
Iceland1999Iceland649
Iceland1998Iceland566
Iceland1997Iceland694
Iceland1996Iceland850
Iceland1995Iceland865
Iceland1994Iceland1039
Iceland1993Iceland1196
Iceland1992Iceland1149
Norway2019Norwegian coast448476
Norway2018Norwegian coast385460
Norway2017Norwegian coast338455
Norway2016Norwegian coast362455
Norway2015Norwegian coast297
Norway2014Norwegian coast409
Norway2013Norwegian coast511
Norway2012Norwegian coast355
Norway2011Norwegian coast230
Norway2010Norwegian coast159
Norway2009Norwegian coast585
Norway2008Norwegian coast900
Norway2007Norwegian coast905
Norway2006Norwegian coast538
Norway2005Norwegian coast614
Norway2004Norwegian coast549
Norway2003Norwegian coast467
Norway2002Norwegian coast412
Norway2001Norwegian coast466
Norway2000Norwegian coast359
Norway1999Norwegian coast308
Norway1998Norwegian coast83
Norway1997Norwegian coast60
Norway1992-1996Norwegian coastN/A

This database of reported catches is searchable, meaning you can filter the information by for instance country, species or area. It is also possible to sort it by the different columns, in ascending or descending order, by clicking the column you want to sort by and the associated arrows for the order. By default, 30 entries are shown, but this can be changed in the drop-down menu, where you can decide to show up to 100 entries per page.

Carry-over from previous years are included in the quota numbers, where applicable.

You can find the full catch database with all species here.

You can find a complete file with all comments and explanations here, under Overview Documents.

For any questions regarding the catch database, please contact the Secretariat at nammco-sec@nammco.no.

Other Human Impacts

By-catch and entanglements

By-catch of harbour seals during fishing operations and removals near fish farms are the major factors negatively impacting populations of this species in the North Atlantic. Estimating the exact level of by-catch can, however be challenging due to the potential for misidentification of seal species in logbook and inspector reports. This is particularly the case for young seals, where grey and harp seals can be misidentified and reported as harbour seals. There are now attempts underway in some countries to minimise this misidentification through the use of photos and analysis of DNA samples.

In Norway, fisheries of concern for harbour seal by-catch are the gillnet fishery for cod and monkfish. A coastal reference fleet (CRF) for the cod and monkfish gillnet fisheries reports by-catch data and landings. There is a peak of by-catch in the cod fishery in February–April, while the highest levels seen in the monkfish fishery occur from July–December. Although analysis remains ongoing and improvements in precision are still being made, preliminary estimates suggest a by-catch in Norwegian gillnet fisheries of around 450 harbour seals each year (Moan & Bjørge 2020).

In Iceland, the fisheries of most concern regarding marine mammal by-catch are assumed the gillnet fishery for cod and lumpsucker (NAMMCO 2016). In a report from 2019, around 1400 harbour seals are estimated to be by-caught annually in lumpsucker gillnets between 2014–2018, when the estimate is stratified by management area (Marine and Freshwater Research Institute 2019). The most reliable by-catch data for cod gillnets comes from the March–April research survey and from the reports of fisheries observers (1% coverage of the fleet and representative geographical spreading). However, estimating by-catch in cod gillnets remains difficult due to a lack of data outside of April.

In US waters, the total human caused mortality and serious injury to harbour seals for the period 2008-2012 was estimated to be caused by US commercial fisheries on 97 % of the cases (Waring et al. 2015b).

Conflicts with fisheries & aquaculture

In Iceland and Norway, fish farmers have been allowed to remove seals near the farms by shooting them. In 2019, however, national regulations on coastal seals in Norway were amended and it is now prohibited to kill seals near aquaculture facilities. Interactions between seals and fish farms in Iceland are reduced by the use of double-netting. However, there are still some interactions between harbour seals and salmon fisheries around the river mouths, but removals are thought to be low, about 2-3 per year.

Marine traffic

Commercial ship and vessel-based tourism are anthropogenic sources of disturbance for harbour seal colonies, causing potential shifts in local distribution and population decline (Jansen et al. 2015). Similar consequences can be due to habitat degradation caused by increased urbanization (Reijnders 1994).

In the UK between 2008 and 2010, several harbour seals were found stranded with peculiar injuries consisting of a single continuous curvilinear skin laceration spiralling down the body. Similar injuries were previously also observed in Canadian waters. After some investigation, the cause of death was found to be a traumatic event, with the seal being drawn through the ducted propellers of marine vessels (Bexton et al. 2012).

Pollutants

Pollutants are well known to negatively impact marine mammals. The levels of pollutants in harbour seals are generally regarded as low and do not constitute a health threat (Drescher et al. 1977). However, some environmental contaminants (especially persistent organic pollutants and mercury) are known to affect the immune system and might play a role in rendering marine mammal populations vulnerable to disease through immunotoxicity (Mos et al. 2006).

harbour seal resized © Sandra Granquist

NORWAY

Surveys

Regular counts for abundance are carried out along the entire coast of Norway. Visual counts using binoculars from small boats and land are carried out in areas not covered by aerial surveys, or where results from the aerial surveys seemed to be incomplete. In 2016, electric helicopter drones with cameras were added to these survey efforts. The surveys conducted between 2011-2016 revealed a total minimum population of 7712 harbour seals along the mainland Norwegian coast (National Progress Report Norway 2019). In 2017 and 2018, surveys (using drone and visual counts) were conducted from the southernmost point in Norway and along the west coast. The total numbers of harbour seals in each of the counties from Møre and southward were similar to the results in the period 2011-2015, but there was an increase in Trøndelag (National Progress Report Norway 2019). Ship based counting of harbour seals, using electronic helicopter drones with cameras, will be conducted in Northern Norway (Nordland and Troms) in 2020.

Satellite tagging

Researchers from the Norwegian Institute of Marine Research have also tagged 5 harbour seals with GPS phone tags in the southern Oslofjord in mid November 2019. Since being tagging, some of these seals have been moving more into the Oslofjord and others south to Swedish areas (National Progress Report Norway 2019). Tagging will continue in 2020.

Diet & behaviour

Studies on diet, behaviour, and the harbour seal’s role in the ecosystem have also been conducted. In one study by scientists at the Institute of Marine Research on harbour seals in Porsangerfjord diving, movements, and diet were investigated (Ramasco 2016). This study identified that harbour seals perform “resting dives”, a behaviour not previously seen  in this species. Harbour seals were also found to mainly forage during the day in the autumn and spring in Porsangerfjord. When comparing the seals’ diving behaviour to the presence of certain possible prey in the area, it is likely that seals are preferring small fish close to where the seals haul out. Their diet likely also changes with the seasons as different prey become available and when the sea ice forms.

Publications of results from genetic and population studies of harbour seals are also currently in progress (National Progress Report Norway 2018).

ICELAND

In recent years, research in Iceland has focused on getting updated abundance estimates, information on diet and prey selection, genetic and contaminant analysis, as well as information on movements and foraging behaviour in estuaries. Recently, results of a project looking at seal diets in river mouths in the northwest of Iceland was published (Granquist et al. 2018). A master’s project on vocalisations and behaviour of male Icelandic harbour seals during the mating season continued through 2019 (National Progress Report Iceland 2018, 2019).

Decline

A survey of harbour seals was conducted in 2016 and indicated that the population was declining. The potential causes of the decline are not known. It is possible that hunting and by-catch (seals being caught in fishing nets) could be contributing to the decline, but the numbers of hunted and by-caught seals is not well known. Other factors that could be affecting harbour seals are the changes being seen in the ecosystem around Iceland, such as the warming of the water, and the associated northward movement of an important prey species such as the sandeel.

Another potential factor in the decline of harbour seals is disturbance from tourism, and studies by Burns et al. (2018) and Aquino et al. (2018) both look into the ethics of the tourism industry. These factors, and potentially the combination of all of them, are being investigated further by researchers in Iceland at the Marine and Freshwater Institute and the Icelandic Seal Centre. Additionally, work continues towards obtaining reliable estimates of seal by-catch.

Aerial surveys & haul-out behaviour

The latest harbour seal aerial survey was conducted by the MFRI and ISC during 2018 and the analyses were published in 2019 (Granquist and Hauksson 2019). The next aerial census is planned for 2020.

A new project was initiated in 2018 and continued through 2019, monitoring haul-out behaviour using camera traps. This project will assist in improving census design by increasing the knowledge of factors affecting haul-out behaviour (National Progress Report Iceland 2018, 2019). In addition, a study on the effect of land- and boat-based tourism on the spatial and behavioural haul-out patterns of harbour seals was initiated by ISC and MFRI in 2008 and continued during 2019. This study includes cooperation with researchers from Holar University Collage, University of Iceland, Griffith University in Australia, Stockholm University in Sweden. This interdisciplinary research focuses on best practices, management of seal watching and development of an ethical framework (National Progress Report Iceland 2019).

GREENLAND

Harbour seals are rare in Greenland. There are only around 100 seals in the three-known breeding/molting localities. Current research aims to monitor the known sites and to locate the suspected additional sites, since observations of harbour seals far from these areas indicate that there may be some additional small breeding and molting sites not yet detected. An interview study to assist this was initiated in West Greenland in 2019 (National Progress Report 2019). It is important to know the distribution and seasonal cycles of behavior of a given species in order to monitor the populations.

The first telemetry study of deep diving harbour seals in Greenland has deployed 15 satellite-linked data-recorders on 12 individual harbour seals in the southern tip of Greenland across 2 years (Rosing‑Asvid et al. 2020). This study thoroughly describes their movements, dive patterns, haul-out behaviour, and breeding activities. The data collected in this study provides a new dive depth record, with a male reaching 631m. The research also presents a novel way to estimate pregnancy status, position and date of parturition based on telemetry data. The study found that an abrupt reduction of home range and simultaneous changes in both the dive and the haul-out patterns reflected parturition.

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