Construction, calibration, and field test of a home-made, low-cost hydrophone system for cetacean acoustic research

Marine Mammals are reliable bioindicators of aquatic ecosystems health. Since cetacean highly relay on the use of sound for conspecifics interaction, feeding, and navigation, research in bioacoustics becomes fundamental to unravel the influence of anthropogenic activities on their environment and vocal behaviour. Unfortunately, the widespread of studies in this area are often limited for the lack of affordable equipment. This paper first describes how to build a low cost hydrophone suitable for cetacean acoustic research and then shows how to perform hydrostatic pressure tests and acoustic calibrations using easily available tools. Finally, field recordings of individuals of two dolphin species: long-beaked common dolphin (Delphinus capensis) and bottlenose dolphin (Tursiops truncatus) in La Paz Bay, Baja California Sur, Mexico using the proposed hydrophone and a professional hydrophone system [AQ-1s and ITC-1042 transducers (10 Hz - 100 kHz)] are compared.