Dietz, R., Teilmann, J., Andersen S. M. Rigét, F., and Olsen, M. T. 2013. Movements and site fidelity of harbour seals (Phoca vitulina) in Kattegat, Denmark, with implications for the epidemiology of the phocine distemper virus. – ICES Journal of Marine Science, 70:186–195. Twenty-seven harbour seals were caught and tagged at the island of Anholt in central Kattegat, Denmark, the epicentre of the phocine distemper virus (PDV) outbreaks in 1988 and 2002 that killed 50–60% of the populations. The satellite tagging shows that harbour seals from Anholt moved widely across Kattegat with a maximum distance of 249 km from the tagging haul-out site. Overall, females travelled over a wider area compared with males [90% kernel home range (KHR) females, 5189 km2; males, 3293 km2). KHR calculated for yearlings (6414 km2) is larger than for subadults (2534 km2), which again is larger than for adult seals (1713 km2), showing a strong site fidelity, indicating limited gene flow between haul-out sites. Distances moved and home range sizes increased across autumn, peaked in February–March, and decreased through spring. During the breeding season in spring, all seals were very stationary around Anholt. The onset of the PDV epizootics in 1988 and 2002 took place when the Anholt harbour seals congregate on the Island during April. Anholt seal were also documented to have contact with infected seal locations at Hesselø, Læsø, and the Swedish west coast, although this contact takes place during winter prior to the documented summer outbreaks.

ABSTRACT1. In Denmark, harbour seals, Phoca vitulina, were first protected in 1977, and since then a number of seal reserves have been established in Danish waters. The effectiveness of these reserves to prevent human-induced disturbances to the seal population have, however, not been evaluated.2. To evaluate this, experimental disturbances were conducted in one of the most important seal reserves in Denmark (Anholt seal reserve). Specifically, the behavioural responses (alert distance, flight initiation distance, flee distances and flight duration) of harbour seals to approaching pedestrians and boats were studied.3. The project was conducted during three periods related to the breeding cycle of harbour seals. In all periods, harbour seals were alerted by boats at significantly greater distances compared with pedestrians (560-850 m and 200-425 m, respectively). Similar differences in the flight initiation distances were observed, 510-830 m for boats and 165-260 m for pedestrians. In most cases seals were alerted and began to flee when the approaching boat was outside the reserve, whereas seals did not respond to approaching pedestrians until after they had entered the reserve.4. Harbour seals exhibited weaker and shorter-lasting responses during the breeding season. They were more reluctant to flee and returned to the haul-out site immediately after being disturbed, in some cases even during the disturbance. This seasonal tolerance is most likely attributed to a trade-off between fleeing and nursing during the breeding season, and hence not an indication of habituation.5. Based on the results of this study it is suggested that the reserve boundaries on land be placed at least 425 m from the haul-out area and the boundary at sea should extend to at least 850 m from the haul-out area in order to secure adequate year-round protection from disturbances.

This study used hard-part analyses from scats (n = 117) and stomachs (n = 3) to investigate the diet of high Arctic harbour seals (Phoca vitulina L., 1758) living on Prins Karls Forland, Svalbard, in early autumn. Additionally, it compared the results of fatty-acid analyses of the seals' blubber versus that of potential prey with the findings of the more traditional diet assessment method. Svalbard harbour seals appear to be opportunistic, polyphagous feeders similar to the situation in other parts of their range. Members of the cod-family, and secondarily the sculpin-family, dominated the diet of harbour seals on Svalbard. Small fish comprised most of the diet of the harbour seals; invertebrates appeared to be insignificant. Atlantic cod (Gadus morhua L., 1758) was the most important species in the diet in terms of biomass, whereas polar cod (Boreogadus saida (Lepechin, 1774)) was the most frequently consumed prey. Our comparison between hard-part diet analyses and fatty acids is far from definitive, but it indicates a general influence of the diet on the fatty-acid composition of the inner blubber layer. However, it also suggests systematic selective processes in the incorporation of fatty acids into the blubber. Observed differences between the fatty-acid composition of the different blubber layers and possible differences between sex and age classes warrant further investigation.Résumé : Nous avons analysé les structures dures dans les fèces (n = 117) et les estomacs (n = 3) afin d'étudier le ré-gime alimentaire de phoques veaux marins (Phoca vitulina L., 1758) du haut-arctique vivant à Prins Karls Forland, à Svalbard, au début de l'automne. De plus, nous avons comparé les résultats d'analyses d'acides gras du lard des phoques et de leurs proies potentielles avec les résultats des méthodes plus traditionnelles d'évaluation du régime alimentaire. Les phoques veaux marins de Svalbard semblent être des polyphages opportunistes, comme ailleurs dans leur aire de répartition. Le régime alimentaire des phoques veaux marins de Svalbard est dominé par les poissons de la famille de la morue et secondairement de la famille du chabot. Le régime des phoques comprend surtout des poissons de petite taille; l'importance des invertébrés est insignifiante. La morue franche (Gadus morhua L., 1758) est l'espèce la plus importante en ce qui a trait à la biomasse, alors que le saïda franc (Boreogadus saida (Lepechin, 1774)) est la proie la plus fréquemment consommée. Notre comparaison de l'analyse des structures dures et de l'analyse des acides gras est loin d'être définitive, mais elle montre une influence générale du régime alimentaire sur la composition en acides gras de la couche interne de lard. Elle indique aussi, cependant, l'existence de processus sélectifs systématiques dans l'incorporation des acides gras dans le lard. Les différences observées dans la composition en acides gras des différen-tes couches de lard et les différences possibles entre les sexes et les différentes classeâge requièrent des études supp...