Fin whales (Balaenoptera physalus) summering in the Ligurian Sea: distribution, encounter rate, mean group size and relation to physiographic variables

This paper investigates the distribution of Mediterranean fin whales (Balaenoptera physalus) between 1990-99 in recently-established Pelagos Sanctuary for Conservation Marine Mammals. During study period, 870 days were spent at sea, surveying a total 73,046km, totalling 540 sightings whales. Mean yearly whale encounter rates showed no significant differences first five years, but then steadily decreased 1995-99. The highest and largest mean aggregation size (mean=2.12; SD=1.32; SE=1.15) summer 1995 throughout period was 1.75 (mode=1; SD=1.11; SE=0.05). Differences not months. is likely to be related prey availability patchiness plankton distribution. Generalised Linear Models used relate physiographic variables (mean, range standard deviation depth slope, distance from nearest coast). Water most variable describing distribution, with more than 90% occurring waters deeper 2,000m. demonstrates deep water preference this area, emphasises crucial role that part western Ligurian Sea plays ecology provides recommendations conservation management measures area.