Bottlenose dolphins' fin marks comparison highlights limited movements and anthropogenic threats in the waters around Sicily (Italy, Central Mediterranean Sea).

Few information is available on fin marks and movements of Mediterranean bottlenose dolphins, Tursiops truncatus (Montagu, 1821), along the Italian coast, although significant photo-identification efforts took place in several areas. In this study, photographic data (833 images) of 370 dolphins collected by different organizations from 2003 to 2018 across six different areas in Sicily (Southern Italy) were compared. A software was used to measure angles with notches and Dorsal Fin Ratio of dorsal fins. Only 8 matches were identified between neighbouring areas along the south-western coast of Sicily. Additionally, 2 matches were found between the Aeolian Archipelago and the Strait of Messina. A different distribution of the fin mark pattern among dolphins from distinct areas was identified, suggesting different ecological conditions, levels of social interactions and threats. These results support the hypothesis that Mediterranean bottlenose dolphins tend to aggregate primarily with individuals coming from the same sub-area and only few animals roam widely, connecting with different groups in distant areas. The few matches and the distinct fin mark patterns found in this study suggest that fragmented bottlenose dolphin communities might face high risk for their survival due to low movements and local anthropogenic threats. [ABSTRACT FROM AUTHOR]