Core habitats of bottlenose dolphins in the MPA Regno di Nettuno, gulf of Naples, Italy

Species conservation requires a clear understanding of habitat use. The bottlenose dolphin (Tursiops truncatus) is a coastal species subjected to various anthropogenic threats. In this research, we use a combination of behavioral observations and GIS analysis to identify core hotspots for bottlenose dolphins around the Islands of Ischia and Procida. The surveys took place mainly within the Marine Protected Area “Regno di Nettuno” which is organized in five zones with different levels of protection; one of these, the D-zone, is dedicated to marine mammals. Data were collected from 2004 to 2018 by the Ischia Dolphin Project, an ongoing long-term research program on cetaceans. In order to evaluate the use of habitat, GPS coordinates were taken every three minutes during the sightings and then analyzed using QGIS Kernel Density Estimation and Hotspot analysis. We conducted 1186 boat-based surveys (58332 km). During these, we encountered 91 bottlenose dolphin groups and spent 156 hours (877 km) in direct observations. The hotspot maps were created from the analysis of 71 behavioral sequences > 40 min, with a mean duration of 121 min (range 41-417). Feeding hotspots were identified N, NW of Ischia, and NW of Procida; socializing and mating hotspots partially intersected with the feeding ones, but the one NW of Procida was wider; a milling and resting hotspot was located NW of Procida. Core habitats of bottlenose dolphins are only in part protected by the zonation of the Marine Protected Area. More specifically, the hotspots NW of Procida, located on the main route to Naples, are particularly exposed to disturbance from commercial and recreational traffic. Cutting-edge conservation policies can take advantage of this spatial information to increase the safeguard of protected species. In particular, the MPA should use them to revise and enlarge the boundaries of the D-zone dedicated to marine mammals.