1 Background, Grey seal population biology
UK grey seal population in a World context
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- Region Pup Production Years when latest information was obtained
- Europe excluding UK 9,000 Increasing
- WORLD TOTAL 125,600 Increasing
- 7 Non Breeding Distribution within the BNNC-EMS
6. UK grey seal population in a World context The UK grey seal population represents approximately 45% of the world population on the basis of pup production. The other major populations in the Baltic and Canada are also increasing, but at a faster rate than in the UK (Table 2) Table 2. Relative sizes of grey seal populations. Pup production estimates are used because of the uncertainty in overall population estimates
1 Ó Cadhla, O., Strong, D., O’Keeffe, C., Coleman, M., Cronin, M., Duck, C., Murray, T., Dower, P., Nairn, R., Murphy, P., Smiddy, P., Saich, C., Lyons, D. & Hiby, A.R. 2007. An assessment of the breeding population of grey seals in the Republic of Ireland, 2005. Irish Wildlife Manuals No. 34. National Parks & Wildlife Service, Department of the Environment, Heritage and Local Government, Dublin, Ireland. 2 Data summarised in:- Grey Seals of the North Atlantic and the Baltic. 2007 Eds: T. Haug, M. Hammill & D. Olafsdottir. NAMMCO Scientific publications Vol. 6 3 Bowen, W.D., McMillan,J.I. & Blanchard, W. 2007. Reduced Population Growth Of Gray Seals At Sable Island: Evidence From Pup Production And Age Of Primiparity. Marine Mammal Science, 23(1): 48–64 4 Baltic pup production estimate based on mark recapture estimate of total population size and an assumed multiplier of 4.7 5 Thomas,L.,Hammill,M.O. & Bowen,W.D. 2007Estimated size of the Northwest Atlantic grey seal population 1977-2007 Canadian Science Advisory Secretariat: Research Document 2007/082 pp31. 7 Non Breeding Distribution within the BNNC-EMS Outside the breeding season grey seals come ashore regularly to rest and during late winter to moult. Recent telemetry studies indicate that grey seals spend approximately 20% of their time ashore throughout the year. At present there is little information on why seals haulout and on what effects reducing their ability/options for hauling out would have on their individual fitness. A haulout deprivation study on harbour seals indicated that they respond to being prevented from hauling out by increasing the length of subsequent haulout periods. This has been interpreted as indicating a physiological requirement for hauling out (Brasseur et al 1996). A series of aerial surveys of grey seals hauled out on the east coast between Coquet Island and Fraserburgh were carried out between April and September 2008. Locations of haulout sites and counts of seals are presented in Table 3 and figures 7,8 & 9. Grey seal haulout sites are widely distributed on the east coast. Figure 7 shows the distribution from Fraserburgh to Coquet island throughout the spring and summer months in 2008. The area around the Farne Islands and Lindisfarne holds the largest concentration of hauled out seals along this section of coast line in all months. It is approximately 80 km south of the nearest large haulout sites in the Firth of Forth. To the south there is a major haulout site at Coquet Island (an SPA on the southern boundary of the BNNC-EMS) but then no major haulout sites between Coquet Island and the Humber estuary. The BNNC-EMS must therefore be regarded as an important haulout area for grey seals. Figure 8 shows the distribution of haulout sites within the BNNC-EMS and the numbers of seals counted each month during the spring and summer months in 2008. The haulout sites are concentrated around the Farnes and Lindisfarne with one minor haulout site in Newton Bay and the major site at Coquet Island. North of Lindisfarne there were no records of seals hauling out except for three small groups in Berwickshire during the August surveys. There is little obvious seasonal pattern in the haulout distribution. Coquet Island showed a gradual decline in importance during the year, with a large haulout group including a disproportionate number of juveniles in early spring decreasing to zero in the September survey. The complete absence of seal haulout sites along the coast at the Fast Castle breeding site was unexpected as there are haulout sites close to most grey seal breeding sites in the UK. In the case of Fast Castle the most likely explanation is that the local topography does not provide suitable haulout habitat. Whereas access to sheltered and undisturbed beaches is the primary consideration for breeding grey seals haulout site are usually at sites with easy access to open water. The stratigraphy at Fast Castle, with erosion of cliffs with steep incline planes means that there are few suitable haulout rocks. The sheltered beaches have restricted access routes which may reduce their attractiveness to seals. The proximity (50km represents less than half day’s swim for a grey seal) of the large and presumably attractive haulout sites at the Farnes, Isle of May and Firth of Tay and the wide ranging foraging movements of grey seals means that this absence of haulout sites does not indicate a problem for grey seals. Figure 9 shows the fine scale haulout distribution within the Farnes (including Lindisfarne), each month during the spring and summer months in 2008. The distribution of seals in the vicinity of the Farnes and the large scale re-distributions within it suggest that they should be regarded as one haulout site. It is likely that the relative numbers at Lindisfarne and the main Farne Islands is a function of the weather and to a smaller extent a result of increased boat activity and occasional disturbance events at the Farnes during the summer months. It was noteworthy that on the one occasion when few seals were found at Lindisfarne, large numbers were found on the small haulout rocks at Knivestone on the outer fringe of the Farnes. The number of seals hauling out on the sand banks inside Lindisfarne varied through the survey programme, during June and July over 50% of seals counted were at Lindisfarne. Figure (7) Distribution of grey seal at haulout sites along the east coast from Fraserburgh to Coquet Island. Surveys conducted monthly between April and September 2008   
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