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Abstract1. In the United Kingdom (UK), several harbour seal (Phoca vitulina) populations have been declining over the past decade. In order to understand the effect of these changes in abundance, this study seeks to determine the population structure of harbour seals in the UK, and in Scotland in particular, on a wider and finer spatial scale than has previously been reported.2. Harbour seals were genotyped from 18 different localities throughout the UK and neighbouring localities in mainland Europe, at 12 microsatellite loci. Results from Bayesian and frequency based tests of population structure suggested an initial structural division into two main groups consisting of localities in northern UK and southern UK-mainland Europe, respectively.3. These two clusters were further divided into four geographically distinct genetic clusters.4. An overall agreement between the genetic results and the existing management areas for UK harbour seals was observed, but it is also clear that an adaptive management approach should be adopted, in which the delineation of the current management areas is maintained until further genetic and ecological information has been accumulated and analysed.

Grey (Halichoerus grypus) and harbour seals (Phoca vitulina) are sympatric seal species, but they display distinct strategies of habitat use and connectivity between haulout sites. The distribution patterns and variations in relative abundance of both species were investigated along the French coast of the English Channel, at the southern limit of their range where seal numbers are increasing. Regular censuses conducted at all main haulout sites in mainland France showed significant seasonal variations at most sites, with more harbour seals counted during summer (breeding and moulting seasons), and more grey seals during summer only in the eastern English Channel. Trends in maximum haulout numbers at haulout sites showed a significant increase over the last five years, ranging from 9.7 to 30.9% per year for harbour seals, and from 5.8% (in the western English Channel) to 49.2% (in the eastern English Channel) per year for grey seals. These rates of increase in grey seal numbers are not linked to local pup production and most probably result from seal movements from the southwest British Isles and the North Sea, respectively. Aerial surveys conducted across the English Channel showed that most seal observations at sea were concentrated in the northeastern English Channel. Telemetry showed that the 28 harbour seals tracked remained highly coastal, within a radius of 100km from their haulout sites, and did not move to other known colonies. Grey seals moved much greater distances, reaching up to 1200 km from their capture site. More than half of the 45 grey seals tracked crossed the English Channel, especially during the breeding season, moving to known colonies in the southwest British Isles and the North Sea. Combining individual tracks and long-term surveys of the seal populations allowed a better understanding of the dynamics of these populations and their connectivity at a larger regional scale. The findings provide direct information for the management of grey and harbour seals within the frame of the Marine Strategy Framework Directive, and highlight focus areas where potential interactions between the two species should be monitored.

The north-east Atlantic grey seal, Halichoerus grypus, is widely distributed along the European coastline from northern Russia to France, with the core population centred around Scotland. To date, very little is known of the diet of the species at the southern margin of the species range. However, because grey seal numbers have been increasing over the last few decades in France, the issue of their potential interactions with coastal fisheries is frequently raised. The diet of grey seal in the Molène Archipelago was investigated by combining scat, stomach content and fatty acid analyses, since all three approaches have complementary potentials to reveal feeding habits of a predator. A total of 145 scats mostly of moulting adult males, 14 stomach contents of yearlings and 14 blubber samples from animals of all ages were analysed following standard methodologies. Scats revealed a diet mainly constituted of 50.6% by mass (M) of wrasse, Labridae (mostly Labrus bergylta), 20.7%M conger eel, Conger conger, and 11.9%M sea bass, Dicentrarchus labrax. Stomach contents were made up of 52.3%M cuttlefish, Sepia officinalis, 9.5%M sole, Solea solea, and 9.4 %M conger eel. All these prey are different from the diet observed in core areas. Fatty acid analysis from the blubber confirmed that the diet differed between the Molène Archipelago and one of the Scottish breeding sites. It also showed that most of the inter-individual variability was explained by variation in seal body masses, which could be linked to behavioural ontogeny of foraging strategies. Most of the prey species identified in the food of the grey seal in Brittany are also targeted by professional and/or recreational fisheries in the area; additionally, several prey size-ranges also partly overlap with marketed size-ranges for several species.

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