Large-scale seasonal distribution of fin whales (Balaenoptera physalus) in the central Mediterranean Sea

Abstract

Fin whales (Balaenoptera physalus) are the only mysticete regularly found in the Mediterranean Sea. Its exceptional high abundance during the summer period in the north-western Mediterranean is essentially due to productive waters, but outside of this spatio-temporal window its distribution still remains quite unknown. This paper investigates the distribution of the fin whale on large-scales during the 2002–2006 period. Three areas of the central Mediterranean Sea were selected: the Ligurian Sea in the north-western Mediterranean belonging to the Pelagos Sanctuary; the area connecting both Mediterranean basins in the south-western Mediterranean, the Strait of Messina; and the waters surrounding the island of Lampedusa, in the central Mediterranean. Of the 41,270 km covered by the three surveys, a total of 98 sightings was recorded corresponding to 198 fin whales. Results display a year round distribution along synchronic seasonal dispatching, with a feeding behaviour occurrence in the northern part of the Pelagos Sanctuary during late spring and summer. They indicate high abundance in the Lampedusa area from late winter to early spring manifesting feeding activity. In the Strait of Messina, our results point out the importance of this area as a seasonal feeding ground and an important location for regular autumn transfers between both Mediterranean basins. According to the feeding ground in the two Mediterranean basins, whales change foraging strategy, one being single animals or animal pairs searching for prey in the water column while the other strategy is associated with more individuals feeding on the surface. The strategies differ also by their ecological conditions, such as depth affinity and shoreline distance.