Clymene dolphin (Stenella clymene) whistles in the Southwest Atlantic Ocean

Abstract

The Clymene dolphin despite being endemic for the Atlantic Ocean continues to be the least known species in the genus Stenella without available information on their vocal repertoire in Brazilian waters. Data were obtained during mitigation and monitoring work required by IBAMA under the federal environmental licensing as conditions of the license 108/16 for the 3D seismic survey in Para/Maranhao Sedimentary Basin process 02022.000015/2014. The species record was performed onboard the vessel Polarcus Alima with a Mseis (Night Hawk III) four-element towed array passing signals to a digital M-Audio, recording at 96 kHz/16bits. During visual and acoustic monitoring with the air-guns off, a group of approximate 80 dolphins were sighted and recorded on May 8th, 2016 (00˚38’00” N, 44˚45’25” O) at 3,425 m depth. The wav-files were analyzed through the spectrogram configured as DFT 2048 samples, 70% overlap and Hamming window of 1024 points generated by software Raven Pro 1.5. The results of 14 min recording allowed the extraction of 257 whistles. Minimum frequencies ranged from 5.20 kHz to 15.92 kHz (mean = 10.99 kHz); maximum frequencies ranged from 7.72 kHz to 28.04 kHz (mean = 16.16 kHz); whistle duration ranged from 0.01 s to 1.52 s (mean = 0.43 s). These results are important since they represent the first acoustic record of Clymene dolphins in Brazil.