Fin Whale Presence and Distribution in the Pelagos Sanctuary: Temporal and Spatial Variability Along 2 Fixed-Line Transects Monitored in 2009-2013

Data collected during a 5-year monitoring program carried out midst summer along fixed-line transects in the northern Ligurian sea was used to inspect the variability in the presence and distribution of the Mediterranean fin whale in the Pelagos Sanctuary. The systematic and regular sampling design allowed direct yearly and monthly comparisons. The analysis was conducted at different spatial (regional, sub-regional and local) and temporal (yearly-monthly) scales. Species presence and distribution was then related to changes in ecosystem dynamics, namely the magnitude and spreading of the spring bloom, through near-surface chlorophyll a satellite-derived concentrations as a proxy for near-surface phytoplankton biomass. Results indicate strong inter-annual and intra-seasonal variability of species presence at both regional and sub-regional scales, providing new insights into the use of the area by the species. This variability evidences the role of the target species as effective ecosystem sentinels. The local analyses allow the identification of hotspots, some of which are persistent through time and should therefore, be taken into consideration when defining priority areas for conservation actions.