AN ACOUSTIC APPROACH TO EVALUATE PRESENCE AND ECOLOGICAL STATUS OF CETACEANS IN THE IONIAN SEA

Cetaceans are among the biggest top-predator species and their presence is therefore a useful indicator of the health status of marine environment. Variations in their presence and distribution in a given area, such as the Mediterranean Sea, potentially highlight environmental alterations driven by either biological, chemical, physical or anthropogenic factors. Hence, the development of new cetaceans monitoring techniques actively contributes to promote good management practices of water resources. Since 2005, the INFN (Istituto Nazionale di Fisica Nucleare) has promoted, within the framework of the EMSO and KM3NeT projects, the installation and operation of two cabled deep-sea infrastructures offshore Eastern Sicily, Ionian Sea: the Catania node, at a depth of 2,100 m, 25 km offshore the harbour of Catania and the Capo Passero node, at a depth of 3500 m, 100 km offshore Portopalo di Capo Passero. The two submarine infrastructures are equipped with acoustic arrays for the real time monitoring of the underwater noise. The acoustic signals acquired at the two deep-sea sites have been analysed by means of new software tools, developed on purpose for the automatic detection and classification of the sounds emitted by different cetacean species. The newly-developed software tools brought for the first time to the long-term monitoring of cetaceans presence and vocal behaviour, offshore Eastern Sicily. The acoustic presence of the Mediterranean Sperm whale (Physeter macrocephalus) and Fin whale (Balaenoptera physalus) has been studied over different recording years. In addition, the automatic analysis of the sperm whale “clicks” allowed to reveal the size distribution of the animals occurring in the area. Within the observation areas, the acoustic tracking of biological and anthropogenic noise sources was also possible. Evolving passive acoustic monitoring strategies represents an actual-technological challenge for the protection and management of the marine environment, which asks for increasingly advanced multidisciplinary partnerships.