Residency patterns and site fidelity of Grampus griseus (Cuvier, 1812) in the Gulf of Taranto (Northern Ionian Sea, Central-Eastern Mediterranean Sea)

Abstract

The residency pattern and site fidelity of Risso’s dolphin Grampus griseus were studied using sightings data collected during standardized vessel-based surveys carried out from 2013 to 2018 in the Gulf of Taranto (Northern Ionian Sea, Central-Eastern Mediterranean Sea). The photo-identification of 91 individuals of G. griseus and the occurrence of re-sighted dolphins up to 8 times provide the evidence that this mid-sized odontocetes persistently occurred in the study area. The presence of transient individuals, visitors, and seasonal residents in the Gulf of Taranto, along with the 29 multi-year resident Risso’s dolphins observed from 2 to 4 times on different years, indicated some degree of inter-annual variability in its temporal use of the area. Moreover, the occurrence of newborns and calves through the study period suggests the possibility to consider the Gulf of Taranto as both nursery and feeding area for females caring for their offspring. The importance of the Gulf of Taranto as critical habitat for the Risso’s dolphin as well as the common bottlenose dolphin and the striped dolphin candidates this area as potential Important Marine Mammal Area, in which enforce specific conservation measures are aimed to mitigate the anthropogenic pressure on different cetacean species according to ACCOBAMS and the MMPATF indication.