Development of a prototype underwater acoustic and motion recorder for the Ganges river dolphin

To investigate the clicking frequency and the body motion of the Ganges river dolphin, the authors started to develop a micro data logger that can be attached to the dolphin body and record not only the dolphin's clicks but also the 3D body motion over a 24 hour period. A prototype that consists of a developed hydrophone unit and other general-purpose devices was developed in 2014. The system was mounted on an AUV and its performance was initially tested during the AUV sea trials that were carried out in March 2014. As a result of the sea trials, the motion recorded by the data logger was corresponding to the motion recorded by the AUV well. Sound signals generated from the thrusters of the AUV and the acoustic equipment of the AUV was also recorded. It means that this proto-type data logger has enough performance to record dolphin's motion and clicks sounds. In addition, this data logger is also a useful tool for the evaluation of the noise level of underwater systems such as AUVs or underwater acoustic systems under actual operating conditions.