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Abstract: The development and broad use of passive acoustic monitoring techniques have the potential to help assessing the large-scale influence of artificial noise on marine organisms and ecosystems. Deep-sea observatories have the potential to play a key role in understanding these recent acoustic changes. LIDO (Listening to the Deep Ocean Environment) is an international project that is allowing the real-time long-term monitoring of marine ambient noise as well as marine mammal sounds at cabled and standalone observatories. Here, we present the overall development of the project and the use of passive acoustic monitoring (PAM) techniques to provide the scientific community with real-time data at large spatial and temporal scales. Special attention is given to the extraction and identification of high frequency cetacean echolocation signals given the relevance of detecting target species, e.g. beaked whales, in mitigation processes, e.g. during military exercises. [Copyright &y& Elsevier]

Abstract: In the frame of the European Sea-floor Observatory Network (ESONET) and in preparation of the Demonstration Mission Listening to the Deep-Ocean Environment (LIDO) algorithms for the automated real-time detection, classification and localisation of cetaceans have been developed. Such Passive Acoustic Monitoring techniques have the potential to play a key role in cetaceans’ conservation for they allow a non-invasive study of their behaviour, a better knowledge of their population dynamics, and a better understanding of their dynamic relationship with their environment. This paper investigates the development of efficient and accurate techniques to be used as the basis of a localisation module for an automated real-time Passive Acoustic Monitoring system. An opportunity to assess the capabilities of the developed localisation modules was given by recordings collected with a bottom-mounted (around 2080m depth) tetrahedral compact hydrophone array located offshore the port of Catania (Sicily) during the NEMO-ONDE campaign in the years 2005–2006 by INFN and CIBRA . A well-known class of methods for acoustic source localisation is based on time differences of arrival (TDOA). Its capabilities have shown to be useful even in adverse situations (i.e., few sensors, high noise levels and/or poor calibration). A second class of methods, the space–time methods, originated in underwater applications such as sonar but reached its most significant achievements over the last 20years in digital communications with recent progress in the treatment of broadband signals. These developments are here revisited under the scope of the localisation and tracking of cetacean vocalisations. Various broadband space–time methods were implemented and allowed to map the sound radiated during the detected clicks and to consequently localise both sperm whales and vessels. Hybrid methods were also developed which improved the robustness of space–time methods to noise and reverberation and reduced processing time. In most cases, the small variance obtained for these estimates lessened the necessity of additional statistical clustering. Even though not independently confirmed by sightings, the tracks derived in the proposed frame can be considered to be consistent with the known movements of sperm whales and vessels. [Copyright &y& Elsevier]