X hits on this document

Word document

Marine EcoSystems and Sustainability - page 38 / 41





38 / 41

Long-term variation in harbour seal diet in Orkney (NE Scotland) and relationships with fish abundance

Pierce G.J1,2, Ieno E.N1,3, Santos M.B1,2, Zuur A.F1,3, Edridge A1 & Thompson P.M4

1Oceanlab, University of Aberdeen, Main Street, Newburgh, Aberdeenshire, AB41 6AA, UK;

2Instituto Español de Oceanografía, Centro Oceanográfico de Vigo, P.O. Box 1552, 36200, Vigo, Spain;

3Highland Statistics Ltd, 6 Laverock Road, Newburgh, Ellon, Aberdeenshire, AB41 6FN, UK

4Lighthouse Field Station, University of Aberdeen, George Street, Cromarty, Ross-shire, IV11 8YJ, UK

Long time series of dietary data can potentially provide information on how predator diets respond to changing prey abundance, e.g. due to overfishing and/or climate change. The present study examines long-term variation in the summer diet of harbour seals (Phoca vitulina) in Orkney (NE Scotland), based on faecal sampling at haulout sites on the island of Eynhallow during 1986-2006. In summer, haulouts are used mainly by harbour seals while grey seals (Halichoerus grypus) use the island mainly in autumn and winter. Samples were collected in the summers of 1986-88, 1993-96, 1998, 2000-03 and 2005-06. The main component of the diet in summer is sandeels (Ammodytidae, mainly Ammodytes spp.). Average sandeel size in the diet increased by around 6% over the study period while numbers of sandeels in scats declined. Both harbour seal and sandeel abundances have fallen markedly since the mid-1990s but, although dietary trends were statistically significant, harbour seal diet has remained remarkably constant over the study period, suggesting a degree of dietary specialization. Thus harbour seals in Orkney may currently depend on sandeels as their main food source.

Document info
Document views143
Page views143
Page last viewedTue Jan 17 19:56:14 UTC 2017