Abstract
The Mediterranean sub-population of bottlenose dolphin (Tursiops truncatus) is classified as vulnerable by the International Union for Conservation of Nature. This species is strictly protected in France and the designation of Special Areas of Conservation (SAC) is required by the European Habitats Directive (HD, 92/43/EEC). However, little information is available on the population in French Mediterranean waters.The objective of this thesis is to provide elements for the elaboration of a conservation strategy for the bottlenose dolphin in the French Mediterranean Sea, by improving the knowledge of the population and by evaluating the potential of the network of marine protected areas (MPA) for its conservation.To study the distribution, abundance and structure of the population, we analyzed photo-identification data collected throughout the year on the entire French Mediterranean shelf between 2013 and 2015 as part of the GDEGeM project.We observed 151 bottlenose dolphin groups, resulting in the photo-identification of 766 dolphins. The distribution of encounter rates showed the presence of bottlenose dolphins throughout the continental shelf throughout the year. We estimated for the first time, using capture-recapture methods, the population size of bottlenose dolphins frequenting the continental shelf of Provence and the Gulf of Lion at 2,636 individuals (95% CI: 2,051-3,514). Our results were used to support the designation of a new Site of Community Importance (SCI) dedicated to the species in the Gulf of Lion and provide a baseline for the monitoring of bottlenose dolphins in French Mediterranean waters in the context of the Marine Strategy Framework Directive (MSFD, 2008/56/EC) and the HD.The study of the social structure of the population frequenting the French Mediterranean continental shelf using network analyses revealed 4 social clusters along the continental coasts. The evaluation of home ranges showed that 3 clusters preferentially use the Gulf of Lion, while the 4th cluster preferentially uses the coasts of Provence. No association was observed between dolphins observed in Corsica and dolphins observed in the Gulf of Lion and in Provence, suggesting an independent social community in this area. These results call for considering 3 regional units for the monitoring and conservation of bottlenose dolphins in French Mediterranean waters.About thirty marine protected areas are distributed along the coast of the Gulf of Lion, Provence and Corsica. In order to evaluate the potential of this network for the conservation of the bottlenose dolphin population, we evaluated the coverage of the network of marine protected areas (MPAs) in the 3 regions by comparing encounter rates and relative abundances of bottlenose dolphins inside and outside the MPAs. The results show that in Corsica and in the Gulf of Lion, the network should be completed, while in Provence, it appears adequate. We also evaluated the consideration of the bottlenose dolphin in the MPAs through a questionnaire submitted to the managers. The answers showed that, although the bottlenose dolphin is present in all the MPAs that responded (90%), almost none of them carry out any monitoring or conservation measures for the species. The responses also highlighted the needs of the managers in terms of knowledge, means of action and collaborations.The results of this thesis constitute a solid basis and provide recommendations to allow the elaboration and the implementation of a conservation strategy for the bottlenose dolphin population at the scale of the French Mediterranean coast by enhancing the MPA network.