Cuvier's beaked whale distribution in the Mediterranean Sea: results from small boat surveys 1996–2007

Abstract

A total of 17,651 km of sailboat survey effort obtained with very good sighting conditions was pooled over the period 1995 to 2007 to provide an insight into Cuvier's beaked whales' (Ziphius cavirostris) distribution in the western and central Mediterranean Sea. Although only six confirmed sightings were obtained under such conditions, complementary sightings made a total of eleven confirmed records. Their distribution showed that only slope habitat, and its close proximity, was favourable to the species. In contrast to regions pointed out in the recent literature, such as the Alboran, Ligurian and Ionian Seas, it appeared that the Tyrrhenian Sea was likely to be an important area for Cuvier's beaked whales in the Mediterranean. Sighting rates of 0.1–0.25 sighting/100 km and sighting rates for individuals of 0.2–0.5 individual/100 km were obtained in favourable regions. When compared to sighting rates obtained on Risso's dolphinsGrampus griseusduring the same surveys, the Cuvier's beaked whale appeared to be quite a frequent species in its favoured habitats. The present study contributes a better knowledge of this poorly-known species, in the context of increasing and threatening anthropogenic noises.