DISTRIBUTION, ABUNDANCE AND SEASONALITY OF CETACEANS SIGHTED DURING SCHEDULED FERRY CROSSINGS IN THE CENTRAL TYRRHENIAN SEA - 1989-1992

The results of a medium-term survey of cetaceans in the central Tyrrhe nian Sea, the first ever all-year-round one to be made in the Mediterr anean, are reported. Individuals of Balaenoptera sp. were sighted thro ughout the year, although with significant seasonal differences, in ag reement with the hypothesis of a resident population making seasonal m igrations around, but remaining inside the Mediterranean Sea. Striped dolphins (Stenella coeruleoalba), the most frequently observed species , are present all year round with no significant seasonal differences. Some observations on the presence and group structure of bottlenose d olphins (Tursiops truncatus) and Cuvier's beaked whale (Ziphius caviro stris) are reported. Individuals of four other species (Physeter macro cephalus, Grampus griseus, Globicephala melaena and Delphinus delphis) were also sighted.