SMRU NC-NPG activities to fulfil NERC's Statutory Duties for the Provision of Scientific Advice on the Management of Seal Populations

NERC has statutory obligations under the Conservation of Seals Act (1970) and the Marine (Scotland) Act 2010 to provide the UK government and devolved administrations with scientific advice on the management and conservation of its seal populations. This legislation is the means by which the UK strives to meet the targets set by the UK Marine Strategy and ensure its seal populations, both the grey and harbour seal, are not adversely affected by human activities in the marine environment. Seals have often come into conflict with humans, particularly in relation to fisheries but also increasingly with respect to other marine activities such as the development of marine renewable energy and major infrastructure projects. In conjunction with other statutory obligations, particularly the OSPAR Convention, the UK government and devolved administrations must ensure these listed species achieve a 'favourable conservation status', and understand their population trends and the drivers of change to help determine whether the UK seas are in 'good environmental status'. In order to meet these requirements, NERC tasks the Sea Mammal Research Unit (SMRU) with addressing the questions it receives about the status of the populations and the drivers of population change from UK government each year.

To achieve this, SMRU carries out a programme of monitoring to determine the population status and trends of both species of UK seal. Because of the different life history and behaviour of the two seal species, different methods are required. Harbour seals are counted on land during their moult period in August when the highest proportion of animals are available to count. Around most of Scotland these surveys are carried out using helicopters with thermal imaging cameras, this is because seals are more difficult to see against their rocky shore habitat. On the east coast of the UK where harbour seals are mostly hauled out on sandbanks, these are carried out using fixed wing aircraft with handheld oblique photography. These counts are scaled up to estimates of population size using scalars to represent the proportion of the population onshore. Grey seals are also counted during these surveys, but these counts are more variable due to variation in the proportion of seals at sea during the surveys. The grey seal population is estimated via counts of pups. These are carried out at breeding colonies representing over 90% of UK pup production, every two to three years. Each colony is surveyed multiple times (usually five) in a given breeding season to estimate pup production using a model that combines counts with information on the observation process (probability of detecting a pup, and of correctly classifying it) and life history traits (age at which pups complete moult, age at which they leave the colony) to derive a birth curve and estimate pup production. A time series of pup production estimates and available estimates of population size (from the scaled August counts) are input into a Bayesian age-structured model to examine trends in population size, and to assess the degree to which density dependence is acting on first year survival.

In addition SMRU conducts underpinning scientific research to understand the effect of different marine activities and developments on the two seal species. UK government also needs to understand the natural factors that cause population trends to change and to determine when species may have reached the limits to their growth. In close consultation with government agencies and statutory nature conservation bodies, SMRU responds to the emerging issues relating to seal conservation and provides innovative ways to understand the movements, at-sea behaviour, population structure and impact of natural and man-made factors on their populations at a regional management level.