Conservation des habitats marins soumis à des usages multiples: Méthodes, objectifs et contraintes pour l’optimisation d’un réseau d’Aires Marine Protégées en Manche Orientale

The eastern English Channel is a significant economic area that supports a number of human-based activities, such as tourism and recreational activities, international ports and shipping, and the extraction of both living and mineral resources. In addition, the region supports a number of important marine biological features and large habitat diversity. Marine Protected Areas (MPAs) are increasingly used as a management tool to foster a sustainable exploitation of marine resources in an ecosystem based management framework. All European countries have a legal obligation to develop MPA networks in their national waters. However, there has to date been only limited attempts to coordinate the design and positioning of such networks at an international level and the use of a systematic conservation planning approach is now recommended. This process aims to propose a coherent MPA network, even in a trans-boundary context as in the eastern English Channel (EEC). The studies conducted in this thesis contribute to the scientific knowledge needed to support both anthropogenic activities and conservation objectives in the eastern English Channel. The representation of the whole biodiversity of the eastern English Channel is important in a context of an integrated conservation approach. With this objective, to complete the existing benthic typologies, a pelagic typology was produced and validated with various pelagic species distribution data to ensure that the total biodiversity of the eastern English Channel would be considered. Marxan and Zonation, two widely used conservation planning software packages that provide decision support for the design of reserve systems were compared in the MPA network design process in the EEC. It was found that Marxan was most suitable for subsequent analyses in this thesis because it found reasonably efficient and clear solutions to the problem of selecting a system of spatially cohesive sites that met a suite of biodiversity targets, and the results were easily interpretable. However, Marxan needs ecologically relevant conservation targets to ensure a good representation of the biodiversity to conserve. Thus, habitat conservation targets were calculated using habitat-specific species area relationships. Habitat targets are influenced by various parameters such as sample size or the precision level of the habitat classification used. It was demonstrated here that data quantity, but also data quality and relevance to the considered habitat were affecting the results. Moreover, it was found that MPAs based only on benthic habitats may not be fully appropriate to conserve pelagic habitats. Then, as it is an essential step in a conservation planning approach, a gap analysis was realized at the scale of the EEC. The currently proposed network met conservation targets proposed in this thesis and was found to cover 33% of the EEC. However, a correct assessment of management gaps was not possible as a major part of these MPA do not have management rules yet. te l-0 08 71 86 4, v er si on 1 10 O ct 2 01 3 Finally, the influence of the human activity data on the MPA design process was studied using landings and fishing effort data. Other information on maritime traffic, aggregate extraction or offshore windmills zones, and on-going MPA projects were also added to consider the whole set of uses and regulations that generate spatial constraints in the eastern English Channel. In the context of implementing the Marine Strategy Framework Directive and of developing conservation areas in European waters, the different studies conducted during this thesis may help inform conservation managers in the EEC by testing and applying novel methodologies which are still seldom used in the marine realm.