Presenza acustica di beluga (Delphinapterus leucas) alle Svalbard (Norvegia)

In the last decades the Arctic region has been hugely affected by human-induced changes that led to increasing temperatures and ice-melting processes. In the light of these alterations, it is important to deepen the knowledge of the species strictly dependent from ice occurrence: in particular marine mammals can be considered sentinel species for these environmental changes. The purpose of this thesis is to study the acoustic presence of beluga whales (Delphinapterus leucas) in Kongsfjorden (Svalbard Islands, Norway) and to analyze its temporal occurrence along months, seasons and different light conditions, considering also their movement patterns in the fjord through spatial scale. Data were collected from April 2014 to August 2016 with autonomous passive acoustic recorders by researchers from the Institute for the study of Anthropogenic Impacts and Sustainability in the Marine Environment of the National Research Council of Italy. The recorders were set in three sites: at the mouth of the fjord (B), in front of Ny-Ålesund village (C) and near the Kronebreen glacier (A). In site B, 14371 recordings were analyzed both automatically and visually. To assess the acoustic presence, only clicks were taken into consideration and for every occurrence they were visually counted. Results show 60 acoustic presences of beluga whales in site B, without significant differences across months, seasons and light conditions, even though there are trends with higher presence rates in the months of February, March, October and November, in autumn season and in the dark condition. Also the number of counted clicks showed trends revealing higher numbers in the autumn season, in the dark condition, and in the months of August and September with a peak in October, with the lowest numbers in the summer months and in the light condition. Beluga whales could click more in the darkness, when they cannot rely on visual cues. Acoustic presences detected in the three sites (A, B and C) showed that the animals did not enter and move in the fjord following always the same path, although passages from site C to site B were the most frequent, followed by the ones from site B to C. This work is an explorative analysis that may serve as a key point to study the occurrence of beluga whales in the area and for examining how it can be affected by different natural or anthropogenic factors.