Healthy & Biologically Diverse Seas Evidence Group: Evaluation and gap analysis of current and potential indicators for seals
(August 2010)
Callan Duck



Indicators provided by monitoring programmes of UK grey and harbour (common) seal populations are reviewed as a contribution to the Healthy and Biologically Diverse Seas Evidence Group (HBDSEG) and to the OSPAR / UKMMAS assessment framework. This review focuses on indicators currently in use in policy and regulatory mechanisms and identifies other indicators that could provide useful additional information on seals and their use of the seas around the UK.


There are three indicators currently in use for UK seals.  Two are based on existing, long-term monitoring of UK populations of grey and harbour seals.  The third is based on long-term studies of grey seal population demography at two important breeding colonies in Scotland.  The three existing indicators do not show the direct responses of seals or seal populations to anthropogenic pressures.  Instead, they are indicators of state, showing the responses of seals (in terms of numbers of pups born, moulting population size and female body condition) to the condition of their marine environment over the preceding year (or years).   Four additional indicators that are not assessed routinely but are useful as indicators of the marine environment around the UK are identified.  These suggested indicators respond more directly to specific anthropogenic pressures.


All three currently used indicators were developed to satisfying NERC’s statutory obligations under the Conservation of Seals Act 1970.  They provide the information required by the Countryside Agencies and JNCC to satisfy EU habitats Directive requirements for Special Areas of Conservation designated for grey and harbour seals in the UK.  Two of these indicators are used by OSPAR as EcoQO’s for assessing North Sea grey and harbour seal population status.


In the assessment, all three existing indicators scored ‘highly’ in terms of their scientific value and ‘poorly’ in terms of economic value.  This is because the monitoring programmes cover a very large component of the UK population of each species and require aerial platforms to conduct surveys.  The programmes are designed to determine annual changes in local populations and, necessarily, it takes weeks or months to collect, analyse and assess the results.  The same is true for the longitudinal demographic studies, where individual breeding females are sampled in successive years to determine changes in breeding performance over their lifetime.





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A4, softback, 33 pp
ISBN 978-1-86107-616-8
Please cite as: Callan Duck, (August 2010), Healthy & Biologically Diverse Seas Evidence Group: Evaluation and gap analysis of current and potential indicators for seals, A4, softback, 33 pp, ISBN 978-1-86107-616-8