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When aerial surveys will not do: grey seal pup production in cryptic habitats of Wales

Published online by Cambridge University Press:  12 March 2013

Thomas B. Stringell ,
Colin P. Millar ,
William G. Sanderson ,
Stephen M. Westcott  and
Mandy J. McMath
Thomas B. Stringell*
Affiliation:
Marine and Freshwater Ecosystems Group, Countryside Council for Wales, Maes y Ffynnon, Ffordd Penrhos, Bangor, Gwynedd, Wales LL57 2DW, UK Centre for Ecology and Conservation, College of Life and Environmental Sciences, University of Exeter, Penryn, Cornwall, England TR10 9EZ, UK
Colin P. Millar
Affiliation:
Marine Scotland Science, Scottish Government, Marine Laboratory, PO Box 101, 375 Victoria Road, Aberdeen, Scotland AB11 9DB, UK
William G. Sanderson
Affiliation:
Marine and Freshwater Ecosystems Group, Countryside Council for Wales, Maes y Ffynnon, Ffordd Penrhos, Bangor, Gwynedd, Wales LL57 2DW, UK School of Life Sciences, Heriot-Watt University, Edinburgh, Scotland EH14 4AS, UK
Stephen M. Westcott
Affiliation:
Marine and Freshwater Ecosystems Group, Countryside Council for Wales, Maes y Ffynnon, Ffordd Penrhos, Bangor, Gwynedd, Wales LL57 2DW, UK
Mandy J. McMath
Affiliation:
Marine and Freshwater Ecosystems Group, Countryside Council for Wales, Maes y Ffynnon, Ffordd Penrhos, Bangor, Gwynedd, Wales LL57 2DW, UK
*
Correspondence should be addressed to: T.B. Stringell, Marine and Freshwater Ecosystems Group, Countryside Council for Wales, Maes y Ffynnon, Ffordd Penrhos, Bangor, Gwynedd, Wales LL57 2DW, UK email: t.stringell@ccw.gov.uk
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Abstract

Grey seals (Halichoerus grypus) are a species of conservation concern that require Marine Protected Area management and population status assessment under the EU Habitats Directive. Aerial surveys are commonly used to monitor grey seal pup production at their globally important UK colonies. However, in Wales more than half of pups are born in cryptic breeding habitats such as sea caves. These cryptic habitats preclude the use of aerial monitoring methods and necessitate ground-based counts, which are costly in resources. In this study, we compare a ground-based pup production census with a reduced effort plot-sampling survey to estimate pup production, derive a total population size and assess cost effectiveness. Pup production in North Wales was estimated at 91 (95% confidence interval: 70–112) by the plot-sampling design and was a good approximation of the ‘true’ value of 96 derived from the census. The total population size in North Wales was estimated at between 242 and 307 grey seals. The plot-sampling design reduced survey effort by 46% and saved 30% on logistical costs compared to the full census. We outline the suitability of this method as part of a monitoring programme for grey seal pup production and suggest our approach may be applicable to other regions where grey seals use cryptic breeding habitat.

Keywords

grey seals (Halichoerus grypus)Special Areas of Conservation (SAC)EU Habitats Directivemonitoringabundance estimationplot-samplingcavespup productionWales
Type
Research Article
Information
Journal of the Marine Biological Association of the United Kingdom , Volume 94 , Issue 6 , September 2014 , pp. 1155 - 1159
Copyright
Copyright © Marine Biological Association of the United Kingdom 2013 

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References

REFERENCES

Anderson, S.S. (1977) The grey seal in Wales. Nature in Wales 15, 114–123.Google Scholar
Baines, M.E., Earl, S.J., Pierpoint, C.J.L. and Poole, J. (1995) The west Wales grey seal census. CCW Contract Science Report, no. 131, 238 pp.Google Scholar
Bowen, W.D., McMillan, J. and Mohn, R. (2003) Sustained exponential population growth of grey seals at Sable Island, Nova Scotia. ICES Journal of Marine Science 60, 1265–1274.CrossRefGoogle Scholar
Borchers, D.L., Buckland, S.T. and Zucchini, W. (2002) Estimating animal abundance: closed populations. London: Springer.CrossRefGoogle Scholar
Cronin, M.A., Duck, C.D. and O'Cadhla, O. (2007) Aerial surveying of grey seal breeding colonies on the Blasket Islands, Co. Kerry, the Inishkea Group, Co. Mayo and the Donegal Coast, Ireland. Journal for Nature Conservation 15, 73–83.CrossRefGoogle Scholar
Davies, J.L. (1949) Observations of the grey seal (Halichoerus grypus) at Ramsey Island, Pembrokeshire. Proceedings of the Zoological Society, London 119, 673–92.CrossRefGoogle Scholar
Duck, C.D. (2009) Grey seal pup production in Great Britain and Ireland in 2008. Scientific Advice on Matters Related to the Management of Seal Populations: 2009. St Andrews: Sea Mammal Research Unit. SCOS Briefing Paper 09/1, 12 pp.Google Scholar
Duck, C.D. and Thompson, D. (2007) The status of grey seals in Britain. In Haug, T., Hammill, M. and Olafsdottir, D. (eds) Grey seals in the North Atlantic and the Baltic. Trømso: North Atlantic Marine Mammal Commission, NAMMCO Scientific Publications, Volume 6, pp. 69–78.Google Scholar
Haug, T., Hammill, M. and Olafsdottir, D. (2007) Grey seals in the North Atlantic and the Baltic. Trømso: North Atlantic Marine Mammal Commission.Google Scholar
Hewer, H.R. (1957) A Hebridean breeding colony of grey seals (Halichoerus grypus Fab.) with comparative notes on the grey seals of Ramsay Island, Pembrokeshire. Proceedings of the Zoological Society, London 128, 23–66.CrossRefGoogle Scholar
Hewer, H.R. (1974) British seals. Glasgow: William Collins.Google Scholar
Hiby, L. and Duck, C. (2003) Estimates of the size of British grey seal Halichoerus grypus population and levels of uncertainty. NAMMCO Scientific Committee Working Group on Grey Seals, SC/11/GS/14. Annual report 2003.Google Scholar
Horvitz, D.G. and Thompson, D.J. (1952) A generalization of sampling without replacement from a finite universe. Journal of the American Statistical Association 47, 663–685.CrossRefGoogle Scholar
JNCC. (2005) Common standards monitoring guidance for marine mammals. Version May 2005. Peterborough: JNCC, 36 pp.Google Scholar
Kiely, O., Ligard, D., McKibben, M., Connolly, N. and Baines, M. (2000) Grey seals: status and monitoring in the Irish and Celtic Seas. Maritime Ireland/Wales INTERREG Report no.3, 76 pp.Google Scholar
Leeney, R.H., Broderick, A.C., Mills, C., Sayer, S., Witt, M.J. and Godley, B.J. (2010) Abundance, distribution and haul-out behaviour of grey seals (Halichoerus grypus) in Cornwall and the Isles of Scilly, UK. Journal of the Marine Biological Association of the United Kingdom 90, 1033–1040.CrossRefGoogle Scholar
Matthiopoulos, J., McConnell, B., Duck, C. and Fedak, M. (2004) Using satellite telemetry and aerial counts to estimate space use by grey seals around the British Isles. Journal of Applied Ecology 41, 476–491.CrossRefGoogle Scholar
Neyman, J. (1934) On the two different aspects on the representative method: the method of stratified sampling and the method of purposive selection. Journal of the Royal Statistical Society A 97, 558–606.CrossRefGoogle Scholar
Special Committee on Seals (SCOS) (2010) Scientific advice on matters related to the management of seal populations: 2010. St Andrews: Sea Mammal Research Unit, SCOS Main Advice 2010, 26 pp.Google Scholar
Smith, E.A. (1966) A review of the world's grey seal population. Journal of Zoology (London) 150, 463–489.CrossRefGoogle Scholar
Strong, P.G., Lerwill, J., Morris, S.R. and Stringell, T.B. (2006) Pembrokeshire marine SAC grey seal monitoring 2005. CCW Marine Monitoring Report, no. 26, unabridged version (restricted under license), 54 pp.Google Scholar
Thompson, S.K. (1992) Sampling. New York: Wiley.Google ScholarPubMed
Westcott, S.M. (2002) The distribution of grey seals (Halichoerus grypus) and census of pup production in North Wales 2001. CCW Contract Science Report, no.499, 150 pp.Google Scholar
Westcott, S.M. and Stringell, T.B. (2003) Grey seal pup production for North Wales, 2002. CCW Marine Monitoring Report, no.5, 57 pp.Google Scholar
Westcott, S.M. and Stringell, T.B. (2004) Grey seal distribution and abundance in North Wales, 2002–2003. CCW Marine Monitoring Report, no.13, 80 pp.Google Scholar
Wood, S.A., Brault, S. and Gilbert, J.R. (2007) Aerial surveys of grey seals in the northeastern United States. In Haug, T., Hammill, M. and Olafsdottir, D. (eds) Grey seals in the North Atlantic and the Baltic. Trømso: North Atlantic Marine Mammal Commission, NAMMCO Scientific Publications, Volume 6, pp. 117–122.Google Scholar
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