engleski

Estimation of the bottlenosed dolphin (Tursiops truncatus) population in the Croatian part of the Adriatic Sea.

The aim of thestudy was to estimate the total number of bottlenosed dolphins - Tursiops truncatus (Montagu 1821), the size and composition of dolphin schools, the number of cubs, and their spatial distribution in the Croatian part of the Adriatic Sea in winter. We also wanted to record the presence of any other species of cetaceans and other sea mammals. Aerial survey of dolphin were performed on 27 December 1998 by four small aircraft from an altitude of 200 m and at airspeed of 150-200 km/h. During eight hours we surveyed 45.8% of totaly 31, 660 km2 of the Croatian part of the Adriatic Sea. We saw 16 different bottlenosed dolphin schools comprising a total number of 80 different adult and 8 cubs. We calculated that in the whole of the Croatian part of the Adriatic Sea there were 40 dolphin schools comprising a total number of 218 specimens (202 adult and 16 cubs). In the winter period in question, dolphin cubs accounted for 10% of the population, while 31.3% of dolphin schools had one or more cubs that were smaller by about one-third of their body lenght compared to adults. Average school size was 5.5. The estimated abundance of bottlenosed dolphins in the Croatian part of the Adriatic Sea was: in inshore waters 10.7/1, 000 km2, and in offshore waters 3.3/1, 000km2. Only one sighted school was in offshore waters, 19.0 km from the nearest coast. Not one specimen of any other marine species was observed. This research was the first counting and first study of seasonal (winter) distribution and density of bottlenosed dolphins in the Adriatic Sea.

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