Long-term residency of Tursiops truncatus in the Gulf of Taranto (Northern Ionian Sea, Central-eastern Mediterranean Sea)

Photo-identification data of Tursiops truncatus in the Gulf of Taranto were collected from 2013 to 2018, providing information on its residency pattern and spatial distribution in the study area. On a total of 1117 dolphins observed through the study period, 92 individuals were distinctly identified. Among them, 57 were re-sighted up to fourteen times and the occurrence of 36 individuals re-sighted in different years provides the evidence of multi-year resident, occasional visitor and transient individuals. These results suggest an important inter-annual variability in the habitat use of the study area and emphasize the importance of the Gulf of Taranto as suitable habitat for T. truncatus. Although the majority of the identified dolphins seem to prefer shallower waters within 200 m, 26 individuals have been re-sighted on upper slope grounds, suggesting the occurrence of an offshore ecotype in the study area. Further studies are necessary to investigate driving forces influencing seasonal residency and site fidelity patterns of this dolphin species.