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Variation in harbour seal counts obtained using aerial surveys

Published online by Cambridge University Press:  12 February 2010

Louise Cunningham*
Affiliation:
Sea Mammal Research Unit, Gatty Marine Laboratory, University of St Andrews, St Andrews, Fife, KY16 8LB, Scotland, UK The Scottish Government, Victoria Quay, Edinburgh, EH6 6QQ, Scotland, UK
John M. Baxter
Affiliation:
Scottish Natural Heritage, Silvan House, 3rd Floor East, 231 Corstorphine Road, Edinburgh, EH12 7AT
Ian L. Boyd
Affiliation:
Sea Mammal Research Unit, Gatty Marine Laboratory, University of St Andrews, St Andrews, Fife, KY16 8LB, Scotland, UK
*
Correspondence should be addressed to: L. Cunningham, Sea Mammal Research Unit, Gatty Marine Laboratory, University of St Andrews, St Andrews, Fife, KY16 8LB, Scotland email: lc66smru@gmail.com

Abstract

Aerial surveys of harbour seals (Phoca vitulina) are usually carried out to provide an index of population size. This can be normalized, either by design or by post-hoc analysis to reduce the effects that date, time of day, tide and weather might have on the number of seals counted. In order for long-term trends to be determined from these counts it is assumed that the mean number of seals at a particular site does not vary during the survey period, and that the start and duration of the survey window does not vary with location or between years. This study used a combination of repeat land-based and aerial surveys to test the assumption for constancy of counts during the survey period. The study focused on harbour seal abundance at haul-out sites around the Isle of Skye in north-west Scotland. The coefficient of variation in these counts was estimated to be 15%, based on repeat aerial surveys using thermal imaging. Land-based counts were used to examine the effect of covariates on seal numbers using generalized additive modelling. This site-specific model predicted that the current aerial survey window for harbour seals in the UK, which is a three-week period during the moult, is about a week too early and that count variation could be reduced by surveying 1 1/2 hours earlier in the tidal cycle. Furthermore, the pupping period showed even higher (though more variable) abundance of hauled out seals than during the moult.

Type
Research Article
Copyright
Copyright © Marine Biological Association of the United Kingdom 2010

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References

REFERENCES

Allen, S.G., Ainley, D.G., Page, G.W. and Ribic, C.A. (1984) The effect of disturbance on harbor seal Phoca vitulina haul out patterns at Bolinas Lagoon California USA. Fishery Bulletin 82, 493500.Google Scholar
Boily, P. (1995) Theoretical heat flux in water and habitat selection of phocid seals and beluga whales during the annual molt. Journal of Theoretical Biology 172, 235244.CrossRefGoogle Scholar
Bonner, W.N., Vaughan, R.W. and Johnston, L. (1973) The status of common seals in Shetland. Biological Conservation 5, 185190.CrossRefGoogle Scholar
Boveng, P.L., Bengtson, J.L., Withrow, D.E., Cesarone, J.C., Simpkins, M.A., Frost, K.J. and Burns, J.J. (2003) The abundance of harbor seals in the Gulf of Alaska. Marine Mammal Science 19, 111127.CrossRefGoogle Scholar
Bowen, W.D., Ellis, S.L., Iverson, S.J. and Boness, D.J. (2003) Maternal and newborn life-history traits during periods of contrasting population trends: implications for explaining the decline of harbour seals (Phoca vitulina), on Sable Island. Journal of Zoology 261, 155163.CrossRefGoogle Scholar
Brown, R.F. and Mate, B.R. (1983) Abundance, movements and feeding habits of harbor seals (Phoca vitulina) at Netarts and Tillamook Bays, Oregon. Fishery Bulletin 81, 291301.Google Scholar
Burnham, K.P. and Anderson, D.R. (2002) Model selection and multimodel inference: a practical information–theoretic approach, 2nd edition. New York: Springer-Verlag.Google Scholar
Cunningham, L. (2007) Investigating monitoring options for harbour seals in Special Areas of Conservation in Scotland. PhD dissertation. University of St Andrews, UK.Google Scholar
Cunningham, L., Baxter, J., Boyd, I.L., Duck, C., Lonergan, M., Moss, S. and McConnell, B. (2009) Harbour seal movements and haul out patterns: Implications for monitoring and management. Aquatic Conservation: Marine and Freshwater Ecosystems 19, 398407.CrossRefGoogle Scholar
Daniel, R.G., Jemison, L.A., Pendleton, G.W. and Crowley, S.M. (2003) Molting phenology of harbor seals on Tugidak Island, Alaska. Marine Mammal Science 19, 128140.CrossRefGoogle Scholar
Dietz, R., Heide-Jørgensen, M.-P. and Härkönen, T. (1989) Mass deaths of harbor seals (Phoca vitulina) in Europe. Ambio 18, 258264.Google Scholar
Frost, K.J., Lowry, L.F. and Ver Hoef, J.M. (1999) Monitoring the trend of harbor seals in Prince William Sound, Alaska, after the Exxon Valdez oil spill. Marine Mammal Science 15, 494506.CrossRefGoogle Scholar
Godsell, J. (1988) Herd formation and haul-out behavior in harbor seals (Phoca vitulina). Journal of Zoology 215, 8398.CrossRefGoogle Scholar
Gray, J.S. and Bewers, J.M. (1996) Towards a scientific definition of the precautionary principle. Marine Pollution Bulletin 32, 768771.CrossRefGoogle Scholar
Grellier, K., Thompson, P.M. and Corpe, H.M. (1996) The effect of weather conditions on harbour seal (Phoca vitulina) haulout behaviour in the Moray Firth, northeast Scotland. Canadian Journal of Zoology 74, 18061811.CrossRefGoogle Scholar
Gulland, F.M.D. and Hall, A.J. (2007) Is marine mammal health deteriorating? Trends in the global reporting of marine mammal disease. EcoHealth 4, 135150.CrossRefGoogle Scholar
Harding, K., Härkönen, T. and Caswell, H. (2002) The 2002 European seal plague: epidemiology and population consequences. Ecology Letters 5, 727732.CrossRefGoogle Scholar
Härkönen, T. and Heide-Jørgensen, M.-P. (1990) Short-term effects of the mass dying of harbour seals in the Kattegat-Skagerrak area during 1988. Zeitschrift für Saugetierkunde—International Journal of Mammalian Biology 55, 233238.Google Scholar
Härkönen, T., Harding, K.C. and Lunneryd, S.G. (1999) Age- and sex-specific behaviour in harbour seals Phoca vitulina leads to biased estimates of vital population parameters. Journal of Applied Ecology 36, 825841.CrossRefGoogle Scholar
Harris, D.E., Lelli, B. and Gupta, S. (2003) Long-term observations of a harbor seal haul-out site in a protected cove in Casco Bay, Gulf of Maine. Northeastern Naturalist 10, 141148.CrossRefGoogle Scholar
Harwood, J. and Grenfell, B. (1990) Long term risks of recurrent seal plagues. Marine Pollution Bulletin 21, 284287.CrossRefGoogle Scholar
Heide-Jørgensen, M.P., Härkönen, T., Dietz, R. and Thompson, P.M. (1992) Retrospective of the 1988 European seal epizootic. Diseases of Aquatic Organisms 13, 3762.CrossRefGoogle Scholar
Huber, H.R., Jeffries, S.J., Brown, R.F., DeLong, R.L. and Van Blaricom, G. (2001) Correcting aerial survey counts of harbor seals (Phoca vitulina richardsi) in Washington and Oregon. Marine Mammal Science 17, 276293.CrossRefGoogle Scholar
Jemison, L.A. and Kelly, B.P. (2001) Pupping phenology and demography of harbor seals (Phoca vitulina richardsi) on Tugidak Island, Alaska. Marine Mammal Science 17, 585600.CrossRefGoogle Scholar
Jemison, L.A., Pendleton, G.W., Wilson, C.A. and Small, R.J. (2006) Long-term trends in harbor seal numbers at Tugidak Island and Nanvak Bay, Alaska. Marine Mammal Science 22, 339360.CrossRefGoogle Scholar
Jennings, S., Kaiser, M.J. and Reynolds, J.D. (2001) Marine fisheries ecology. Oxford: Blackwell Publishing.Google Scholar
Jensen, T., van de Bildt, M.W.G., Dietz, H., Andersen, T.H., Hammer, A.S., Kuiken, T. and Osterhaus, A. (2002) Another phocine distemper outbreak in Europe. Science 297, 209.Google ScholarPubMed
Kovacs, K.M., Jonas, K.M. and Welke, S.E. (1990) Sex and age segregation by Phoca vitulina concolor at haul-out sites during the breeding season in the Passamaquoddy Bay region, New Brunswick. Marine Mammal Science 6, 204214.CrossRefGoogle Scholar
Lonergan, M., Duck, C.D., Thompson, D., Mackey, B.L., Cunningham, L. and Boyd, I.L. (2007) Using sparse survey data to investigate the declining abundance of British harbour seals. Journal of Zoology 271, 261269.CrossRefGoogle Scholar
Lucas, Z. and Stobo, W.T. (2000) Shark-inflicted mortality on a population of harbour seals (Phoca vitulina) at Sable Island, Nova Scotia. Journal of Zoology 252, 405414.CrossRefGoogle Scholar
Lunn, N.J., Boyd, I.L. and Croxall, J.P. (1994) Reproductive performance of female Antarctic fur seals: the influence of age, breeding experience, environmental variation and individual quality. Journal of Animal Ecology 63, 827840.CrossRefGoogle Scholar
Olden, J.D., Jackson, D.A. and Peres-Neto, P.R. (2002) Predictive models of fish species distributions: a note on proper validation and chance predictions. Transactions of the American Fisheries Society 131, 329336.2.0.CO;2>CrossRefGoogle Scholar
Pitcher, K.W. and McAllister, D.C. (1981) Movements and haulout behaviour of radio-tagged harbour seals (Phoca vitulina) population in the Dutch Wadden Sea. Journal of Sea Research 12, 164179.Google Scholar
Pitcher, K.W. (1990) Major decline in number of harbor seals, (Phoca vitulina richardsi), on Tugidak Island, Gulf of Alaska. Marine Mammal Science 6, 121134.CrossRefGoogle Scholar
Reijnders, P.J.H. (1986) Reproductive failure in common seals feeding on fish from polluted coastal waters. Nature 324, 456457.CrossRefGoogle ScholarPubMed
Reijnders, P.J.H., Ries, E.H., Tougaard, S., Nøgaard, N., Heidemann, G., Schwarz, J., Vareschi, E. and Traut, I.M. (1997) Population development of harbour seals Phoca vitulina in the Wadden Sea after the 1988 virus epizootic. Journal of Sea Research 38, 161168.CrossRefGoogle Scholar
Schneider, D.C. and Payne, P.M. (1983) Factors affecting haul-out of harbor seals at a site in south-eastern Massachusetts. Journal of Mammology 64, 305520.CrossRefGoogle Scholar
SCOS (2008) Scientific advice on matters related to the management of seal populations: 2008. Special Committee on Seals, University of St Andrews.Google Scholar
Sharples, R.J. (2005) Ecology of harbour seals in southeastern Scotland. PhD thesis. University of St Andrews.Google Scholar
Simpkins, M.A., Withrow, D.E., Cesarone, J.C. and Boveng, P.L. (2003) Stability in the proportion of harbor seals hauled out under locally ideal conditions. Marine Mammal Science 19, 791805.CrossRefGoogle Scholar
Small, R.J., Pendleton, G.W. and Pitcher, K.W. (2003) Trends in abundance of Alaska harbor seals, 1983–2001. Marine Mammal Science 19, 34362.CrossRefGoogle Scholar
Southwell, C. (2005) Optimising the timing of visual surveys of crabeater seal abundance: haulout behaviour as a consideration. Wildlife Research 32, 333338.CrossRefGoogle Scholar
Stewart, B.S. and Yochem, P.K. (1983) Radiotelemetry studies of hauling patterns, movements and site fidelity of harbor seals, Phoca vitulina richardsi, at San Nicolas and San Miguel Islands, California. Hubbs Sea World Research Institute, Technical Report, pp. 83152.Google Scholar
Summers, C.F. and Mountford, M.D. (1975) Counting the common seal. Nature 253, 670671.Google Scholar
Thompson, P. and Rothery, P. (1987) Age and sex difference in the timing of moult in the common seal, Phoca vitulina. Journal of Zoology 212, 597603.CrossRefGoogle Scholar
Thompson, P.M., Fedak, M.A., McConnell, B.J. and Nicholas, K.S. (1989) Seasonal and sex-related variation in the activity patterns of common seals (Phoca vitulina). Journal of Applied Ecology 26, 521535.CrossRefGoogle Scholar
Thompson, P.M. and Harwood, J. (1990) Methods for estimating the population size of common seals (Phoca vitulina). Journal of Applied Ecology 27, 924938.CrossRefGoogle Scholar
Thompson, P.M., Tollit, D., Wood, D., Corpe, H.A., Hammond, P.S. and MacKay, A. (1997) Estimating harbour seal abundance and status in an estuarine habitat in north-east Scotland. Journal of Applied Ecology 34, 4352.CrossRefGoogle Scholar
Thompson, P.M., Van Parijs, S. and Kovacs, K.M. (2001) Local declines in the abundance of harbour seals: implications for the designation and monitoring of protected areas. Journal of Applied Ecology 38, 117125.CrossRefGoogle Scholar
Thompson, D., Lonergan, M. and Duck, C. (2005) Population dynamics of harbour seals (Phoca vitulina) in England: monitoring population growth and catastrophic declines. Journal of Applied Ecology 42, 638648.CrossRefGoogle Scholar
Trillmich, F. and Ono, K.A. (1991) Pinnipeds and El Niño: responses to environmental stress. Berlin: Springer-Verlag.CrossRefGoogle Scholar
Watts, P. (1996) The diel hauling-out cycle of harbour seals in an open marine environment: correlates and constraints. Journal of Zoology 240, 175200.CrossRefGoogle Scholar
Wood, S.N. (2001) mgcv:GAMs and Generalized Ridge Regression for R. R News 1, 2025.Google Scholar
Yochem, P.K., Stewart, B.S., DeLong, R.L. and DeMaster, D.P. (1987) Diel haul-out patterns and site fidelity of harbour seals (Phoca vitulina richardsi) on San Miguel Island, California in autumn. Marine Mammal Science 3, 323332.CrossRefGoogle Scholar
Young, T. (1994) Natural die-offs of large mammals: implications for conservation. Conservation Biology 8, 410418.CrossRefGoogle Scholar