The main type of zonal conservation approach corresponds to Marine Protected Areas (MPAs), which arespatially defined and generally static entities aiming at the protection of some target populations by the implemen-tation of a management plan. For highly mobile species the relevance of an MPA over time might be hampered bytemporal variations in distributions or home ranges. In the present work, we used habitat model-based predicteddistributions of cetaceans and seabirds within the Bay of Biscay from 2004 to 2017 to characterise the aggregationand persistence of mobile species distributional patterns and the relevance of the existing MPA network. We ex-plored the relationship between population abundance and spatial extent of distribution to assess the aggregationlevel of species distribution. We used the smallest spatial extent including 75% of the population present in theBay of Biscay to define specific core areas of distributions, and calculated their persistence over the 14 studiedyears. We inspected the relevance of the MPA network with respect to aggregation and persistence. We foundthat aggregation and persistence are two independent features of marine megafauna distributions. Indeed, strongpersistence was shown in both aggregated (bottlenose dolphins, auks) and loosely distributed species (northerngannets), while some species with aggregated distributions also showed limited year-to-year persistence in theirpatterns (black-legged kittiwakes). We thus have demonstrated that both aggregation and persistence have po-tential impact on the amount of spatio-temporal distributional variability encompassed within static MPAs. Ourresults exemplified the need to have access to a minimal temporal depth in the species distribution data whenaiming to designate new site boundaries for the conservation of mobile species