Mediterranean sea: whales hide in winter (Yahoo)

Why are whales and dolphins, which are so numerous in summer on French and Italian Mediterranean coasts, almost invisible during winter ? The question has been tackled during the 36th congress of the International commission for the scientific exploration of the Mediterranean sea (CIESM) which ended on Friday September 28th at the Grimaldi Forum of Monaco (see Yahoo.fr, "Les baleines de Méditerranée se cachent en hiver").Scientists are wondering “if these cetaceans of the Mediterranean sea are really migrating or if they only move within this sea. For the moment they cannot answer this question, but specialists have a more specified knowledge of the number of each specie present in the north-western part of the Mediterranean basin during summer. The rorqual and the white and blue dolphin are the most common species in the north-western Mediterranean sea. Other species such as the cachalot and the Risso dolphin are also frequent in this sea. Such species go to the International sanctuary for sea mammals opened by the agreement of November 1996, and delimited by French and Italian coasts, from Hyères to Fosso Chiarone and by two lines linking these ports in the north of the Sardinia. But the answer to the question is still very vague. As very few cetaceans cross the strait of Gibraltar to go to America, scientists think that whales stay in more southern regions of the Mediterranean sea, maybe on Tunisian and Libyan coasts.