Assessing the Influence of Environmental and Physiographic Parameters on Common Bottlenose Dolphin (Tusiops truncatus) Distribution in the Southern Adriatic Sea ^†

The Mediterranean subpopulation of common bottlenose dolphins, Tursiops truncatus, is classified as vulnerable by the IUCN Red list due to its decline in population size by at least 50% within the last 50 years. Identifying the spatial distribution and habitat characteristics of this species is crucial to develop effective conservation and ecosystem management strategies. This research is designed to understand the effect of external parameters on the distribution of bottlenose dolphins off the coast of Montenegro. The northern and central Adriatic Sea have been comparably studied since the 1980s, however the southern Adriatic Sea is suffering from a lack of baseline knowledge. Data collected from boat and land surveys over the past 2+ years was utilized to create a Species Distribution Model (SDM). A random forest model incorporating environmental and physiographic variables to represent the dynamic nature of common bottlenose dolphins is applied. These variables include sea surface temperature (SST), salinity, nutrients (Phosphorus and Nitrogen), bathymetry, slope and distance to coast.

The results identified distance to coast, bathymetry, phosphorus and slope as the principal explanatory variables influencing bottlenose dolphin distribution in the southern Adriatic Sea. Bottlenose dolphins were more commonly spotted in shallow waters of <100 m, in areas with a lower degree of slope (0.06 -2.36), with higher phosphorus levels (>0.005 mmol m^-3) and between 760 to 2900 m from the coast of Montenegro.