Harbour seals Phoca vitulina are the characteristic seal of sandflats and estuaries, but are also found on rocky shores in Scotland. As pups swim almost immediately after birth, seals can breed on sheltered tidal areas where banks allow access to deep water. Seals may range widely in search of prey, but individuals often return to favoured haul-out sites.
European status and distribution
Harbour seals Phoca vitulina have a near-circumpolar distribution, with at least four subspecies recognised, from the eastern and western Pacific and eastern and western Atlantic. Only the eastern Atlantic subspecies P. vitulinavitulina occurs in Europe, where its range extends from Iceland and northern Norway southwards to northern France, including the Kattegat/Skagerrak and south-western Baltic. The UK population represents about 5% of the world populationof P. vitulina, approximately 50% of the EU population, and 45% of the European subspecies. The European population has shown a marked recovery after being reduced by a viral epidemic in the late 1980s.
The Harbour seal Phoca vitulina is widespread around the shores of the UK, but population density varies greatly from place to place, with low numbers at many sites. Harbour seal are found from Northern Ireland and the southern Firth of Clyde clockwise round the coast to the Thames estuary. The vast majority of common seal haul-outs are found on the coasts of Scotland, but with an additional important concentration on The Wash, and a smaller number in Strangford Lough, Northern Ireland.
The UK holds at least 33,400 common seals. This is a minimum figure, counted at coastal haul-outs during the moulting period in August. The relationship between this number and total population size has not yet been fully established. Studies in Scotland and the Netherlands suggest that this number represents 60-70% of animals aged one year or older. Applying this correction factor indicates that the total population lies between 48,000 and 56,000.
The complex of skerries, islets, undisturbed mainland shores and offshore islands in north-west Skye consistently support a breeding colony of the Harbour seal Phoca vitulina. The site represents one of the larger discrete colonies of common seals in the UK, holding around 2% of the UK population.
The Dornoch Firth is the most northerly large estuary in Britain and supports a significant proportion of the inner Moray Firth population of the Harbour seal Phoca vitulina. The seals, which utilise sand-bars and shores at the mouth of the estuary as haul-out and breeding sites, are the most northerly population to utilise sandbanks. Their numbers represent almost 2% of the UK population.
The island of Lismore on the west coast of Scotland provides the most sheltered and enclosed site for the Harbour seal Phoca vitulina. Lismore is a composite site comprising five groups of small offshore islands and skerries which are extensively used as haul-out sites by the colony. Seal numbers represent just over 1% of the UK population.
The Firth of Tay & Eden Estuary supports a nationally important breeding colony of Harbour seal Phoca vitulina, part of the east coast population of common seals that typically utilise sandbanks. Around 600 adults haul-out at the site to rest, pup and moult, representing around 2% of the UK population of this species.
The exposed rocky island of Mousa, off the east coast of Shetland Mainland, supports one of the largest groups of Harbour seal Phoca vitulina in Shetland and is one of the most northerly groups in the UK. The large rocky tidal pools on the island are of particular importance, as they are frequently used by the seals for pupping, breeding and moulting, and provide shelter from the exposed conditions on the open coast. The site supports just over 1% of the UK population.
Sanday is situated in the north-east of the Orkney archipelago and supports the largest group of Harbour seal Phoca vitulina at any discrete site in Scotland. The breeding groups, found on intertidal haul-out sites that are unevenly distributed around the Sanday coast, represent over 4% of the UK population. Nearshore kelp beds that surround Sanday are important foraging areas for the seals, and the colony is linked to a very large surrounding population in the Orkney archipelago.
The skerries, islands and rugged coastline of the Inner Hebridean island of Islay hold a nationally-important population of the Harbour seal Phoca vitulina. The south-east coastline areas are extensively used as pupping, moulting and haul-out sites by the seals, which represent between 1.5% and 2% of the UK population.
The Wash, on the east coast of England, is the largest embayment in the UK. The extensive intertidal flats here and on the North Norfolk Coast provide ideal conditions for Harbour seal Phoca vitulina breeding and hauling-out. This site is the largest colony of common seals in the UK, with some 7% of the total UK population.
Yell Sound Coast in the Shetland Islands is the most northerly UK site selected for the Harbour seal Phoca vitulina. The rocky shores and uninhabited islands and skerries within Yell Sound support a colony representing over 1% of the UK population.
SACs where this Annex II species is a qualifying feature, but not a primary reason for site selection