Mark-Recapture method applied by Photo-Identification to a population of bottlenose dolphin (Tursiops truncatus, Montagu 1821) present in the Gulf of Catania

Common bottlenose dolphin (Tursiops truncatus) is known to be a regular species in the Mediterranean, as well as in the waters of the Gulf of Catania, Ionian Sea, as it presents a strong site fidelity. Nevertheless, its population dynamics and social intraspecific relations in Sicily are little known. This research has been conducted within the monitoring project “Dolphin watching and conservation in the Gulf of Catania” led by the Marecamp association from May to October 2019. In order to supervise the health status of a bottlenose dolphin’s local population and to better understand its social structure, it was used the non-invasive photo-identification method, that allowed to capture and recapture these organisms through the natural marks of their dorsal fin. Since this work would like to update to 2019 the Marecamp catalog of this cetacean, all the photos collected have been selected, edited and analyzed using the Darwin software, that compares digital images of the dorsal fins of new dolphins with a database of previously identified dolphin fins. Later, to define the social structure, the Socprog software was utilized and, using association indexes, provided information about the existing interactions among the individuals within the population. During season 2019, 8 individuals were recaptured, while 7 new individuals were captured and added to the catalogue, confirming the residency of this species in the Gulf of Catania, despite the high anthropic impact existing in the area. The social structure analyses instead, confirmed the tendency of this species of forming fission-fusion communities, in spite of the existence of more stabilized couples. In the end, future researches will help to better understand the associations dynamics among individuals and the reasons that led them to establish a certain fidelity to particular subareas and to continue the monitoring of the examined population considering the elevated anthropization of the Gulf.