| Summary: | This work reports the unusual distribution of fin whales and its correlated high mortality along the coast of northwestern Mediterranean, in particular in the Pelagos sanctuary in 2007. Of the 20 sightings occurred along the shore, 6 were juveniles unpaired with their mothers and 4 of them died. First, we detaile dtheir unusual behaviour. All individuals were static, undernourished and covered with a high quantity of parasites (Penella sp.). Most of them entered ports: for instance from 20th to 30th May 2007 we monitored a juvenile fin whale, less than 10m-long, which remained in shallow waters in front of Ligurian coast and entered repeatedly the port of Genova-Voltri, or the whale named “Desirée” that stayed on the French Riviera, from 14th to 24th July 2007. we include videos showing th 10m-long juvenile rustling in Posidonia beds, a behaviour never described yet. The second part of this work deals with general distribution of fin whales in 2007. We estimate the encounter rate of fin whale sightings according to the distance from the coast comparing data from 2004 to 2007, using 121 scientific and 565 whale-watching one-day surveys. Results indicate a significant decline of abundance throughout all 2007. Encounter rate decreases from 1.50 sightings/50 MN in May 2005 to 0.25 sightings/50 MN in May 2007. The last part of this work provides some indications about possible reasons concerning this unusual coastal distribution. We correlate 2007 species distribution with oceanographic parameters such as surface temperature and concentration of chlorophyll, known to be predictive of fin whale distribution. Anomalies of these parameters are mapped showing SST values higher than usual since February (seasonal average = +1°C to +6°C) and an unusual concentration of phytoplankton occuring earlier than previous years. This study may point out some direct global warming impacts influencing top-predator distribution.
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