The persistence in time of distributional patterns in marine megafauna impacts zonal conservation strategies

Abstract

The main type of zonal conservation approaches corresponds to Marine Protected Areas (MPAs), which are spatially defined and generally static entities aiming at the protection of some target populations by the implementation of a management plan. For highly mobile species the relevance of an MPA over time might be hampered by temporal variations in distributions or home ranges. In the present work, we used habitat model-based predicted distributions of cetaceans and seabirds within the Bay of Biscay from 2004 to 2017 to characterise the aggregation and persistence of mobile species distributional patterns and the relevance of existing MPA network. We explored the relationship between population abundance and spatial extent of distribution to assess the aggregation level of species distribution. Specific core areas of distributions were determined, based on predicted distributions, as the smallest spatial extent including 50% of the population present in the Bay of Biscay and their persistence was calculated over the 14 studied years. The relevance of MPA network was assessed regarding aggregation and persistence. The potential to zonal conservation was confirmed for spatially aggregated and persistent species, as bottlenose dolphins or auks. We showed that aggregation level alone is not sufficient to determine candidates to zonal conservation, since some species might be aggregated in space, but poorly persistent in time (black-legged kittiwake). Nonetheless, some loosely distributed species with strong persistence might not benefit from existing zonal conservation due to poor overlap between existing MPA networks and their core areas of distribution (great skuas). We thus have demonstrated that both aggregation and persistence have potential impact on the amount of spatiotemporal distributional variability encompassed within static MPAs. Our results exemplified the need to have access to a minimal temporal depth in the species distribution data when aiming to designate new site boundaries for the conservation of mobile species.