Náttúra og -tilfeingi
Movements of grey seals in Faroese waters
2007 - 2009
Stuðul úr Granskingargrunninum:
Grey seal is the only seal species breeding in Faroe Islands, and the only marine mammal to be found along the coast of the islands throughout the year. Breeding occur in the period late September to November, mainly in caves. A limited hunt occurs on grey seals, in connection with fish farming in the islands. Nevertheless, biological investigations are nearly absent and the present number of seals in the islands is unknown. In order to increase knowledge on grey seals in Faroese waters, a selected number of seals will be caught in nets in their natural habitat and a satellite tag will be glued to the fur on the neck of the seal. Hereby, seals can be tracked in their daily movements on the Faroe Shelf, for up to one year. Each seal track will demonstrate where and when seals move in Faroese waters, when and where seals search their food, when and where they go on land and for how long they stay at sea or on land. Furthermore, long term tracking of ten seals will give the possibility to investigate if there are similarities in the way seals move and feed and where and when they haul-out. Also, it will be investigated if seal movement and behaviour is correlated to strength and direction of the water current. During the breeding season, tracks of mature seals will highlight where seals breed and how long they stay on land during breeding. This is all valuable information in future effort to obtain an abundance estimate of grey seals in the Faroes.
The grey seal is the only Pinniped breeding in the Faroe Islands. The species has not, until now, been subject for any scientific investigations, and there is a lack in knowledge about abundance and distributions. The aim of the present project was to explore the annual movement pattern of grey seals in Faroese waters, and for this purpose position-only satellite transmitters were deployed on ten animals from four selected habitats. The tracking exposed that grey seals are stationary in Faroese waters, and that they have a relatively restricted movement pattern in all seasons. The ten seals were generally distributed at or in the vicinity of their most frequently used haul-out site, but they were also found to make trips of varying durations to one or two alternative haul-out site. Interestingly, all seals were almost solely distributed in waters less than 100m deep during the 123-286 days the tags lasted. Three pregnant females tracked during the project gave birth presumably at the same site they were tagged; and in a period that correlate with a presumed breeding season. The most frequently used haul-out localities were Mykines, Svínoy, Fugloy, Stóra Dímun and Lítla Dímun. The most significant ecological deductions from the project is that the grey seal population in the Faroes has to be considered one closed population and that the grey seal is a top-predator consuming all its annual biomass from the Faroe Shelf ecosystem.
Movements and local site fidelity of grey seals (Halichoerus grypus) in the Faroe Islands. In prep.