Seasonal distribution and abundance of cetaceans within French waters- Part II: The Bay of Biscay and the English Channel

• Published in: Journal of Experimental Biology
• Main Authors: Laran, Sophie, Authier, Matthieu, Blanck, Aurélie, Dorémus, Ghislain, Falchetto, Hélène, Monestiez, Pascal, Pettex, Emeline, Stephan, Eric, Van Canneyt, Olivier, Ridoux, Vincent
• Other Authors: Observatoire PELAGIS UMS 3462 (PELAGIS), LIttoral ENvironnement et Sociétés - UMRi 7266 (LIENSs), Université de La Rochelle (ULR)-Centre National de la Recherche Scientifique (CNRS)-Université de La Rochelle (ULR)-Centre National de la Recherche Scientifique (CNRS), Agence des Aires Marines Protégées, Centre d'Études Biologiques de Chizé - UMR 7372 (CEBC), Université de La Rochelle (ULR)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), APECS (Association pour l’Etude et la Conservation des Sélaciens) France
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2017
• Subjects: English Channel; Bay of Biscay; Cetaceans; Harbour porpoise; Common dolphin; Bottlenose dolphin; Aerial survey; [SDE]Environmental Sciences; baleen whales; minke whale; North Atlantic; Sperm whale
• Online Access: https://hal.archives-ouvertes.fr/hal-01510194; https://doi.org/10.1242/jeb.146928

International audience From the Habitat Directive to the recent Marine Strategy Framework Directive, the conservation status of cetaceans in European water has been of concern for over two decades. In this study, a seasonal comparison of the abundance and distribution of cetaceans was carried out in two contrasted regions of the Eastern North Atlantic, the Bay of Biscay and the English Channel. Estimates were obtained in the two sub-regions (375,000 km²) from large aerial surveys conducted in the winter (November 2011 to February 2012) and in the summer (May to August 2012). The most abundant species encountered in the Channel, the harbour porpoise, displayed strong seasonal variations in its distribution but a stable abundance (18,000 individuals, CV=30%). In the Bay of Biscay, abundance and distribution patterns of common / striped dolphins varied from 285,000 individuals (95% CI: 174,000–481,000) in the winter, preferentially distributed close to the shelf break, to 494,000 individuals (95% CI: 342,000 − 719,000) distributed beyond the shelf break in summer. Baleen whales also exhibited an increase of their density in summer. Sseasonal abundances of bottlenose dolphins were quite stable, with a large number of ‘pelagic’ encounters offshore in winter. No significant seasonal difference was estimated for pilot whales and sperm whale. These surveys provided baseline estimates to inform policies to be developed, or for existing conservation instruments such as the Habitats Directive. In addition, our results supported the hypothesis of a shift in the summer distributions of some species such as harbour porpoise and minke whale in European waters