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Scotland's Marine Atlas: Information for The National Marine Plan

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SEALS

Introduction

Two species of seals (grey seal - Halichoerus grypus, and harbour seal - Phoca vitulina) are found all around Scotland's coast and inshore waters.

Legislation

The Conservation of Seals Act 1970 has been replaced by the Marine (Scotland) Act 2010 which makes it an offence to shoot seals in Scotland. There is provision for licences to be issued for limited seal management if strict legal tests are met where it is necessary to avoid damage to fisheries or fish farms. For the purposes of considering licence applications to shoot seals the coast has been divided into seven seal management areas: East coast, Moray Firth, Orkney and North Coast, Shetland, Western Isles, West Highlands and South-west Scotland. The number of seals licensed to be shot in any seal management area will be determined on an annual basis, based on the most recent data on seal population size and the underlying trend in their numbers.

It is also an offence to intentionally or recklessly harass seals at their haulout sites.

The Council Directive 92/43/ EEC of 21 May 1992, commonly known as the Habitats Directive, requires member states to designate Special Areas of Conservation ( SAC) for the protection of grey and harbour seals. There are currently five grey seal and eight harbour seal SAC in Scotland.

The OSPAR Convention has set in place Ecological Quality Objectives (Eco QOs) to help assess the state of grey and harbour seal populations in the North Sea.

The Eco QO for grey seals is ï¾"Taking into account natural population dynamics and trends, there should be no decline in pup production of grey seals of _10% as represented in a five-year running mean or point estimates (separated by up to five years) within any of nine sub-units of the North Sea. These sub-units are: Orkney; Fast Castle/Isle of May; the Farne Islands; Donna Nook; the French North Sea and Channel coasts; the Netherlands coast; the Schleswig-Holstein Wadden Sea; Heligoland; Kjørholmane (Rogaland)'.

Up to 2009 grey seal pup production was within these limits. Pup production appears to be stabilising in Orkney, and is increasing at the Isle of May/Fast Castle (entirely due to increases at Fast Castle).

Boundaries of seal management areas and harbour seal conservation areas

Boundaries of seal management areas and harbour seal conservation areas

The Eco QO for harbour seals is "Taking into account natural population dynamics and trends, there should be no decline in harbour seal population size (as measured by numbers hauled out) of =10% as represented in a five-year running mean or point estimates (separated by up to five years) within any of eleven sub-units of the North Sea. These sub-units are: Shetland; Orkney; North and East Scotland; South-East Scotland; the Greater Wash/Scroby Sands; the Netherlands Delta area; the Wadden Sea; Heligoland; Limfjord; the Kattegat, the Skagerrak and the Oslofjord; the west coast of Norway south of 62°N'.

In 2009 harbour seal population sizes in all four sub-units in Scotland were outside these limits. Significant declines have been recorded in populations in Shetland, Orkney and South-east Scotland. Numbers of harbour seals in North and East Scotland have also declined on the north coast but have recently shown signs of stabilising in the north-east coast (Moray Firth).

Grey seal Special Areas of Conservation in Scotland (see Protected Areas)

Faray and Holm of Faray (Orkney)
Isle of May (Firth of Forth)
Monach Isles (Outer Hebrides)
North Rona
Treshnish Isles ( NW Strathclyde)

Harbour seal Special Areas of Conservation in Scotland (see Protected Areas)

Ascrib Island, Isay and Dunvegan ( NW Skye)
Dornoch Firth and Morrich More (E Highland)
Eileanan agus Sgeiran Lois More ( NW Strathclyde)
Firth of Tay and Eden Estuary (Fife and Tayside)
Mousa (Shetland)
East Sanday (Orkney)
SE Islay Skerries (W Strathclyde)
Yell Sound (Shetland)

Priority Marine Features

Grey seal (Halichoerus grypus)
Harbour seal ( Phoca vitulina)

Grey seal
Halichoerus grypus

Approximately 36% of the world's grey seals breed in the UK, of which 90% are from colonies in Scotland. The main concentrations are in the Inner and Outer Hebrides and Orkney. Grey seal pup production monitoring started in the late 1950s. Total numbers increased consistently from then until the late 1990s. In recent years there has been a significant reduction in the rate of increase and pup production in some regions is no longer increasing.

Population estimate for grey seals

Region production

2009 pup production

Change in pup from 08/09

Inner Hebrides

3,396

n/a

Outer Hebrides

12,113

-4.7%

Orkney

19,150

+2.1%

Isle of May/Fast Castle

4,047

+21.0%

All other sites including Shetland

3,247

-5.5%

Total

41,953

+1.0%

The estimate of the total grey seal population in the UK in 2009 based on pup production is problematic due to insufficient information on grey seal life history. The best estimate of the UK 2009 grey seal population size is 119,400 (95% CI 92,500 - 156,200) with an estimated Scottish population size of 105,072.

Grey Seals in Scotland by 1km squares, from surveys in August 2007-2009 (Sea Mammal Research Unit)

Grey Seals in Scotland by 1km squares, from surveys in August 2007-2009 (Sea Mammal Research Unit)

UK grey seal pup production at annually
monitored breeding colonies

UK grey seal pup production at annually monitored breeding colonies
Source: Sea Mammal Research Unit

Grey seal pup production at North Sea
colonies in Firth of Forth

Grey seal pup production at North Sea colonies in Firth of Forth
Source: Sea Mammal Research Unit

Grey Seal

Grey Seal
© Lorne Gill/ SNH


Harbour Seal
Phoca vitulina

Approximately 4% of the world's population, or 24% of the European subspecies of harbour seal (also known as common seal) are found in Scotland. Over 80% of the UK harbour seal population is found in Scotland.

Harbour seal numbers have declined dramatically by over 50% in Shetland, Orkney and the east coast of Scotland since 2001, with a smaller decline in the Outer Hebrides, whilst on the west coast and Inner Hebrides numbers have remained relatively stable. The cause/s of these declines are as yet unknown but are under investigation and conservation measures have been introduced.

Population estimate of harbour seals

The minimum population estimate for harbour seals in Scotland is:

Area

Estimate

Year

Trend

Outer Hebrides

1,804

2008

Declining

Scottish west coast

11,364

2007/08/09

Stable/Slight increase

Scottish east and north coast

1,359

2007/08

Declining

Shetland

3,003

2009

Declining

Orkney

2,897

2009

Declining

Total

20,427

Source: Sea Mammal Research Unit

The current estimated total number of harbour seals in Scotland of 20,427 is 31% less than the total of 29,600 for the previous complete survey carried out in 1996/97. The decline in some areas has been much greater than in others, e.g. in Orkney numbers have declined from 8,523 in 1997 to 2,897 in 2009, a decline of 66%, and in the Firth of Tay numbers have declined from a mean of 670 between 1992 and 2002 to 111 in 2009, a decline of 83%.

The harbour seal population over much of the east coast and the Northern Isles has shown a marked decline in recent years, none more so than in the Firth of Tay where there has been an 83% decline from the high in 1992. The cause/s of this decline are still unknown but it is possible that it is due to a combination of a number of factors such as competition with grey seals, reduced prey availability, disease, increased predation from killer whales, shooting, elevated biotoxin loading, and reduced fecundity. In addition in the Firth of Tay in particular, there were a number of unusual deaths caused by massive traumatic corkscrew injuries, similar to injuries seen in a number of harbour seals off Blakeney Point on the east coast of England. Almost 10% of the Firth of Tay female breeding population of harbour seals may have been affected in 2010.

Harbour Seals in Scotland by 1km squares from surveys in August 2007-2009 (Sea Mammal Research Unit)

Harbour Seals in Scotland by 1km squares from surveys in August 2007-2009 (Sea Mammal Research Unit)

Numbers of harbour seals in
Management Areas in Scotland

Numbers of harbour seals in Management Areas in Scotland
Source: Surveys by the Sea Mammal Research Unit

Harbour seals in the Firth of Tay

Harbour seals in the Firth of Tay
Source: SMRU surveys conducted in August, during the annual moult

Harbour seals

Harbour seals
© Lorne Gill/ SNH


Moray Firth Seal Management Plan

The Moray Firth Seal Management Plan was established in 2005 in response to the declining number of harbour seals in the area. Since its inception, numbers have stabilised and begun to rise again. The management plan structure has been considered a success and it has been used as a template for developing the management of seals on other parts of the coast.

Moray Firth harbour seals in August

Moray Firth harbour seals in August
Source: Sea Mammal Research Unit

Pressures

There are a number of potential pressures and activities that may affect seals but the extent and magnitude of most have not been quantified. These include exposure to a range of hazardous substances including hydrocarbons, pathogens introduced from sewage and persistent pollutants such as PCBs. They are also susceptible to entanglement in marine litter and through by-catch in both active and ghost fishing gear. Habitat damage has resulted in a reduction in prey biomass and some loss of breeding habitat. Collisions with shipping and propeller strikes can be fatal and with the increase in offshore renewable energy developments this could increase. Noise from shipping, anti-predator acoustic devices and recreational activities, both at sea and on land, can cause disturbance at haul-out sites. Unregulated shooting in the past has been a source of mortality that it was difficult to quantify but the new measures contained within the Marine (Scotland) Act mean that this should no longer be a problem. Climate change is an unknown pressure at this time, although there is the potential that with increasing sea temperatures the abundance and distribution of preferred prey species may change.

Female grey seal with young pup

Female grey seal with young pup
© Lorne Gill/ SNH

Harbour seal

Harbour seal
© Lorne Gill/ SNH

Harbour seal pup

Harbour seal pup
© Lorne Gill/ SNH

Grey seal underwater

Grey seal underwater
© Sue Scott