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A review of spatial and temporal variation in grey and common seal diet in the United Kingdom and Ireland

Published online by Cambridge University Press:  20 January 2012

Susie L. Brown*
Affiliation:
School of Biological Sciences, Queen's University Belfast, Medical Biology Centre, 97 Lisburn Road, Belfast, BT9 7BL
Stuart Bearhop
Affiliation:
Centre for Ecology and Conservation, School of Biosciences, University of Exeter, Cornwall Campus, Penryn, Cornwall, TR10 9EZ
Chris Harrod
Affiliation:
School of Biological Sciences, Queen's University Belfast, Medical Biology Centre, 97 Lisburn Road, Belfast, BT9 7BL Facultad de Recursos del Mar, Instituto de Investigaciones Oceanológicas, Universidad Antofagasta, Avenida Angamos 601, Antofagasta, Chile
Robbie A. McDonald
Affiliation:
Environment and Sustainability Institute, University of Exeter, Cornwall Campus, Penryn, Cornwall TR10 9EZ
*
Correspondence should be addressed to: S.L. Brown, Department of Zoology, Ecology and Plant Science, Cork Enterprise Centre, University College Cork, Distillery, Fields, North Mall, Cork email: s.brown@ucc.ie

Abstract

Knowledge about the diet of fish-eating predators is critical when evaluating conflicts with the fishing industry. Numerous primary studies have examined the diet of grey seals Halichoerus grypus and common seals Phoca vitulina in a bid to understand the ecology of these predators. However, studies of large-scale spatial and temporal variation in seal diet are limited. Therefore this review combines the results of seal diet studies published between 1980 and 2000 to examine how seal diet varies at a range of spatial and temporal scales. Our results revealed extensive spatial variation in gadiform, perciform and flatfish consumption, likely reflecting variation in prey availability. Flatfish and gadiform consumption varied between years, reflecting changes in fish assemblages as a consequence of factors such as varying fishing pressures, climate change and natural fluctuations in populations. Perciform and gadiform consumption varied seasonally: in addition there was a significant interaction between season and seal species, indicating that grey and common seals exhibited different patterns of seasonal variation in their consumption of Perciformes and Gadiformes. Multivariate analysis of grey seal diet revealed spatial variation at a much smaller scale, with different species dominating the diet in different areas. The existence of spatial and temporal variation in seal diet emphasizes that future assessments of the impact of seal populations should not be based on past or localized estimates of diet and highlights the need for up-to-date, site specific estimates of diet composition in the context of understanding and resolving seal/fisheries conflict.

Type
Research Article
Copyright
Copyright © Marine Biological Association of the United Kingdom 2012

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