Cetacean in the Pelagos Sanctuary: Need for a multi-scale management approach

We use 5-years summer data (2009-2013 late May-end of September) systematically collected along fixed transects crossing the Pelagos Sanctuary (PS-Northwestern Mediterranean). We examine species habitat preferences at different spatial/temporal scales. Broader patterns are investigated separately in the western and eastern region of PS. To allow direct comparison, yearly/monthly indexes of species presence are computed as a proportion of the encounter rate of the species in a region and the overall ER for the species in the PS (indexregion_sp_y/m=ERregion_sp_y/m/ERPS_sp where ER=n sightings/hours on effort). Habitat variability is examined using maps of the phytoplankton bloom, obtained by 1-km maps of sea surface chlorophyll distribution. At a finer scale, a 5km grid is used to map yearly/monthly species aggregation areas within each region.Strong-interannual variability is shown, with the alternation of ‘rich’ (eg.2010-2012-2013) and ‘poor’ years (eg.2009-2011). Striped dolphin (sc) and fin whales (bp) in the eastern region well reflect this pattern, while they show stability and constant increase, respectively, in the western region. Monthly indexes show no pattern for sc while reflect migratory movements from/into PS of fin whales. Cuvier’s beaked whale (zc) peaks of presence coincide with lowest presence of sperm whales (pc), both yearly and monthly, evidencing spatial and temporal habitat partitioning among the two species. Risso’s dolphin show strong fluctuations in the eastern region and is more rare in the western, while pilot whales are almost stable in both regions over the years, showing strong monthly preferences. Bottlenose dolphins alternate rich to poor years in both regions, with a preference for the eastern region and early summer months. Aggregation hot-spots are species specific. Bp and pc hotspots vary both yearly both monthly, while zc hotspots are consistent among years. Based on these results we propose a multi-scale approach for themanagement of thePelagos Sanctuary