Long term monitoring of dolphin’s vocalization in the Gulf of Catania

The SMO (Submarine Multidisciplinary Observatory) project born to develop new technologies in high depth underwater acoustics for biological, high energy astrophysics and geophysical studies. In synergy with the EMSO (European Multidisciplinary Seafloor And Water Column Observatory) framework, the project led to the collaboration of INFN and INGV (Istituto Nazionale di Geofisica e Vulcanologia) to promote the installation of cabled deep-sea infrastructures offshore Eastern Sicily. Data were acquired continuously in different months of 2005, 2006 and 2012 by the two submarine stations of NEMO-OnDE and SN1-EMSO, at a depth of 2100 m, 25 km off the Catania port. The stations were equipped with oceanographic, geological and acoustic sensors (hydrophones).The hydrophones installed sampled acoustic data with a rate of 5min per hour and the information was sent directly to the on-shore laboratory. In order to investigate the presence of delphinidae species in the area, recordings have been studied through both listening and spectrograms analysis. Over the three years, the two platforms worked in the period between July and December, allowing us to perform a statistical survey on the occurrence of dolphins sounds in the acquired data. The dolphin’s acoustic repertory is highly variable and throughout the analyzed files we detected all types of sounds they emit: click, whistles, castanets and buzzes. The present study revealed significant differences in vocal production within the 24 hours and between the investigated periods. We also ascertained that dolphins were present in the study area for around 50% of the recordings analyzed. Thanks to future long term acoustic monitoring it will be possible to better understand the observed variations and to assess if there is any correlation with environmental variables or anthropogenic agents.