Presenza acustica nel tempo delle più grandi specie di Balenotteridi in un fiordo Artico e le loro interazioni con l'attività antropica

Human-induced changes are modifying the Arctic region by the rising of temperatures and the increasing of the ice-melting process. Both resident and migratory marine mammal species can be affected by these environmental changes and have to cope with the anthropogenic exploitation of previously inaccessible areas. The purpose of this study is to examine the acoustic occurrence of the largest Balaenopteridae species, with particular focus on fin whale (B. physalus), in order to assess the yearly and diel distribution of their vocalizations in Svalbard Islands (Norway). Furthermore, the presence and sources of the low frequency underwater noise caused by anthropogenic activities were studied and possible interactions were evaluated. Data used during the study were collected from September 2015 to July 2016 in the Kongsfjorden with an autonomous acoustic recorder. All the data were processed and analyzed both manually and with an automatic detector, previously set up for matching local whale calls. Results showed that fin whales were present in the Kongsfjorden all year round, while blue whale (Balaenoptera musculus) vocalizations never occurred during the 11 months analyzed. The hourly detection of fin whale acoustic presence showed the highest percentage during summer, especially in July, while the vocalization rate was higher during fall and winter, because of the occurrence of continuous songs. Anthropogenic noise was generated all year round by vessel traffic and during a period of two months by airguns. Vocalizations were more detected in absence of anthropogenic noise. During songs, the peak of frequency of each call showed a slight increase with increasing noise, either was natural or anthropogenic. This study highlights variations in the migratory pattern of fin whales compared to what revealed previously, and possible effects in avoiding noise both temporary and structurally. Therefore, more detailed studies are needed to better understand the consequences of human impact on Arctic species in order to preserve them.