A Permanent Automated Real-Time Passive Acoustic Monitoring System for Bottlenose Dolphin Conservation in the Mediterranean Sea

Abstract

Within the framework of the EU Life+ project named LIFE09 NAT/IT/000190 ARION, a permanent automated real-time passive acoustic monitoring system for the improvement of the conservation status of the transient and resident population of bottlenose dolphin (Tursiops truncatus) has been implemented and installed in the Portofino Marine Protected Area (MPA), Ligurian Sea. The system is able to detect the simultaneous presence of dolphins and boats in the area and to give their position in real time. This information is used to prevent collisions by diffusing warning messages to all the categories involved (tourists, professional fishermen and so on). The system consists of two gps-synchronized acoustic units, based on a particular type of marine buoy (elastic beacon), deployed about 1 km off the Portofino headland. Each one is equipped with a four-hydrophone array and an onboard acquisition system which can record the typical social communication whistles emitted by the dolphins and the sound emitted by boat engines. Signals are pre-filtered, digitized and then broadcast to the ground station via wi-fi. The raw data are elaborated to get the direction of the acoustic target to each unit, and hence the position of dolphins and boats in real time by triangulation.

Hydroacoustic System in a Biomimetic Underwater Vehicle to Avoid Collision with Vessels with Low-Speed Propellers in a Controlled Environment

“…The goal of a hydroacoustic system is uninterrupted collision avoidance, which is why recorded signals cannot be analyzed offline, as they were for the sperm whale tracking system presented in Reference [2], where recorded data were saved and archived in a memory card and then analyzed after the completion of the mission. With the BUV2, measurements must be made in real time, and in the case of collision detection, the course and/or depth of the vehicle must change.…”

“…In an underwater environment, hydrophones can be widely used for seismic exploration [1], tracking the movement of marine mammals [2], the directional angle estimation of underwater acoustic sources [3], communications purposes [4,5], and the autonomous navigation of underwater vehicles [6], etc.…”

ARION System for coastal dolphin conservation: A tool for real-time dolphin passive acoustic monitoring in the Portofino Marine Protected Area

“…The acoustic unit consists of a particular type of bottom-moored, solar-powered marine floating structure, named "meda elastica" (elastic beacon), equipped with a 4-sensor array in its submerged part and a control turret on top of the emerged part (see Figure 2) (Brunoldi et al, 2016). The structure is composed of a main pole, about 30 meter length, emerging for 7 meters, with a floating element 6 meters depth.…”

“…The algorithm for the dolphin detection and tracking (Brunoldi et al, 2016) is based on the identification of whistles, the social communication sound emitted by this cetacean. Whistles are detected through the real time analysis of the spectrogram of the hydrophone signals.…”

“…The boat tracking algorithm is based on the cross-correlation method (Fillinger et al, 2011) and on custom-made improvements made to it (Brunoldi et al, 2016). It obtains the direction of the acoustic source, through the cross-correlation signals of two different hydrophone pairs.…”