Modellizzazione e predizione della distribuzione della balenottera comune (Balaenoptera physalus) nel Mar Mediterraneo Occidentale

The fin whale (Balaenoptera physalus) is a cosmopolitan species, with a resident population in the Mediterranean Sea, mainly in the western part of the basin. Sensitivity of the species to disturbing factors, such as ship traffic, microplastic pollution and global warming has increased the need to collect data about the its distribution in order to better evaluate possible threats to its conservation. The aim of this work, part of a collaborative project among the University of Torino and the WWF Italy, was to model the seasonal distribution of fin whales in the western Mediterranean Sea and identify the most predictive environmental variables. The datasets regarding the presence of the species have been provided by different research groups (and shared through the Intercept platform managed by the Acquario di Genova, and through EmodNet), and are made up of samplings carried out from 1998 to 2019. The environmental variables derived from physiographic and satellite databases such as GEBCO, Copernicus and Marspec. The Maxent software was used to model data. Models that excluded less than 15% of points beyond 30 km from the boundary of the predicted areas were validated and their performance in relation to the sensitivity loss and ecological relevance was estimated. Results showed that the distribution of whales in the western Mediterranean was linked to environmental variables that best explained the potential distribution of their main food (mainly zooplankton). These variables were chlorophyll concentration and the intensity of surface currents, where the values for highest predictive presence showed low chlorophyll concentrations (0-0.5 mg/l) and low surface current velocities (>-0.1, <0.1 m/sˉ¹). Surface temperature and salinity had a different influence along the months. Models showed that the most relevant area for the species is the Corso-Ligure-Provencal basin. However, the Center Thyrrenyan sea, and the southern part of the western Mediterranean (Lampedusa, the Strait of Messina, the Algerian-Tunisian coasts, the African continental slope south of Sicily and Malta) emerged as hot spots during both summer and winter. This results can shed light on the movements patterns of the species in the western Mediterraean Sea.