Grey and harbour seals in France: distribution at sea, connectivity and trends in abundance at haulout sites

• Published in: Deep Sea Research Part II: Topical Studies in Oceanography
• Main Authors: Vincent, Cécile, Huon, Mathilde, Caurant, Florence, Dabin, Willy, Deniau, Armel, Dixneuf, Stéphane, Dupuis, Laetitia, Elder, Jean-François, Fremau, Marie-Hélène, Hassani, Sami, Hemon, Audrey, Karpouzopoulos, Jacky, Lefeuvre, Cécile, Mcconnell, Bernie J., Moss, Simon E.W, Provost, Pascal, Spitz, Jérôme, Turpin, Yannis, Ridoux, Vincent
• Other Authors: LIttoral ENvironnement et Sociétés (LIENSs), La Rochelle Université (ULR)-Centre National de la Recherche Scientifique (CNRS), Centre d'Études Biologiques de Chizé - UMR 7372 (CEBC), Institut National de la Recherche Agronomique (INRA)-La Rochelle Université (ULR)-Centre National de la Recherche Scientifique (CNRS), Université des Antilles et de la Guyane (UAG), UMR 228 Espace-Dev, Espace pour le développement, Institut de Recherche pour le Développement (IRD)-Université de Perpignan Via Domitia (UPVD)-Avignon Université (AU)-Université de La Réunion (UR)-Université de Montpellier (UM)-Université de Guyane (UG)-Université des Antilles (UA), Laboratoire d'Etude des Mammifères Marins (LEMM), Océanopolis Brest, Sea Mammal Research Unit, University of St Andrews Scotland, Observatoire Avifaune de la ZPS Estuaire et Marais de la Basse Seine (Maison de l'Estuaire), Observatoire pour la Conservation de la Mégafaune Marine (PELAGIS), La Rochelle Université (ULR)-Centre National de la Recherche Scientifique (CNRS)-La Rochelle Université (ULR)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2017
• Subjects: Tracking; Telemetry; Density; Census; Management units; English Channel; MSFD; OSPAR; [SDE]Environmental Sciences; Phoca vitulina
• Online Access: https://hal.science/hal-01509674; https://doi.org/10.1016/j.dsr2.2017.04.004

International audience 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 north-eastern English Channel. Telemetry showed that the 28 harbour seals tracked remained highly coastal, within a radius of 100 km 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 ...