THE RESIDENT BOTTLENOSE DOLPHIN POPULATION IN NORTH WESTERN ADRIATIC: STUDY BY A SMALL TRANSECT SURVEY

The north western coast of Adriatic sea is characterized by high level of urbanization, an intensive touristic season, overfishing and high ship traffic. Such a strong fishing effort is severely impacting ecosystems and it is the major direct (bycatch) or indirect (food competition) threat for cetaceans. In the area the most common marine mammal is the bottlenose dolphin Tursiops truncatus. A series of random trips with small boats were carried out in April and May 2010 in the area between the river Po delta and river Reno estuary, for 268 hours and 1079 nautical miles of transects. Eleven percent of observation time was spent in areas between 1 to 5 miles from the shore, 38% from 5,1 to 10, 6% from 10,1 to 15, 29% from 15,1 to 25 and 16% from 25,1 to 35 miles of distance. Sightings were 2 in April, one with 1 adult specimen and one with 3 adults, and 4 in May, one with 3 bottlenose dolphins and three encounters with groups of 10, 15 and 35 specimens respectively. The distance from the coast was equally distributed between the distance ranges 1-5 miles, 10-20 miles and 20-30 miles. No correlation with meteorological and sea condition were found. This first results confirm the presence of a viable population of bottlenose dolphins in the area. Further observations will be dedicated to understand if there is one large group or independent sub-units along the whole 150 km coastal area and to start a photo identification activity that can help understanding movement, social structure and conservation necessities.