Report 602
Review of analytical approaches for identifying usage and foraging areas at sea for harbour seals
Jones, E.L., Smout, S., Russell, D.J.F., Pinn, E.H. & McConnell, B.J.
This report describes an analytical approach used to estimate synoptic UK harbour seal at-sea usage, based on telemetry-derived movement data and on terrestrial haul-out surveys. An example of ongoing studies into the identification of harbour seal foraging areas is presented for The Wash.



Since 1988, the Sea Mammal Research Unit’s (SMRU) surveys of harbour seals around the Scottish coast have been carried out on an approximately five-yearly cycle.  Exceptions are the Moray Firth (between Helmsdale and Findhorn), and the Firth of Tay and Eden Estuary SAC, which have been surveyed annually since 2002 (Duck et al 2015).  Surveys carried out in 2006 revealed significant declines in harbour seal numbers in Shetland, Orkney and elsewhere along the UK coast. Between 2007 and 2009, SMRU surveyed the entire Scottish coast including a repeat survey of some parts of Strathclyde and Orkney. In 2010, Orkney was surveyed again to determine whether previously observed declines had continued. The next complete survey of Scotland began in 2011 and was due for completion in 2015. A complete survey of Northern Ireland and the Republic of Ireland was carried out in 2011 and 2012. 

In England, the Lincolnshire and Norfolk coast holds approximately 90% of the English harbour seal population and is usually surveyed twice annually during the August moult.  Since 2004, additional breeding season surveys (in early July) of harbour seals in The Wash (which lies within the August survey area) were undertaken for Natural England.  The Suffolk, Essex and Kent coasts were last surveyed by SMRU during the breeding season in 2011 and during the August moult.

These surveys reveal that harbour seal populations have been in decline in some areas around the UK since 2000.  The population estimate for 2013 was 36,500 (approximate 95% CI 29,900 - 49,700) (Duck et al 2014), and the species is considered to have an unfavourable conservation status in UK waters (JNCC 2013). Reduced juvenile survival and fecundity have been identified as proximate causes of the decline in the Moray Firth, north east Scotland (Matthiopoulos et al 2014). An ongoing investigation by SMRU into the decline of harbour seals around Scotland has identified other possible causes of the decline to include interactions with grey seals (Halichoerus grypus) (indirectly through competition for resources and/or directly through predation) (Brownlow et al 2016) and exposure to toxins from harmful algae (Jensen et al 2015).

The purpose of this report is to build upon the outputs of work undertaken by the Sea Mammal Research Unit (SMRU, University of St Andrews) funded by the Department of Energy and Climatic Change (DECC) and the Scottish Government, in order to draw these strands of work together with the aim of identifying whether discrete and persistent foraging areas for harbour seals (Phoca vitulina) can be identified in the UK marine area.


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ISSN 0963-8901
Please cite as: Jones, E.L., Smout, S., Russell, D.J.F., Pinn, E.H. & McConnell, B.J., (2017), Review of analytical approaches for identifying usage and foraging areas at sea for harbour seals, JNCC Report 602, ISSN 0963-8901