The creation of networks of interconnected highly protected marine areas is one way of increasing population resilience and halting the long-term loss of biodiversity in the oceans.

In this study, we evaluated the efficiency of systematic conservation planning (SCP) varying the adequacy resulting from connectivity in the fragmented hard bottom habitat in the Gulf of Lion. Twelve sets of conservation plans with objectives of conserving 10% and 30% of the hard bottom habitat surface were established by crossing current pressures with three types of connectivity : (i) structural connectivity (ii) early summer and (iii) late summer connectivity arising from a one week larval dispersal, considering or disregarding existing highly protected areas. These connectivities are likely estimates of the functional connectivity of two umbrella species, the gorgonians Eunicella singularis and Leptogorgia sarmentosa. The efficiency of each conservation plan in protecting populations in the Gulf of Lion was then assessed against independent observations of the spatial distribution of the two species. When functional connectivity replaced structural connectivity, the spatial distribution of highly protected areas was significantly modified targeting sites in the central Gulf of Lion, and the efficiency (ratio of proportion of individuals under protection to protection cost) increased by 300 % (20 %, respectively) in the objective of conserving 10% (respectively, 30%) of the hard bottom habitat surface. Moreover, SCP was more focussed when functional connectivity replaced structural connectivity. The present study suggests that using marine functional connectivity is all the more important that the conservation target is low.