Cetacean acoustic survey using towed array in the western South Atlantic shelf break

Abstract

Passive acoustic towed array during ship surveys has being applied to increase the knowledge about cetacean. From 2012 to 2015, towed arrays were used to investigate cetacean distribution along the western South Atlantic shelf break. Research cruises were performed between 26°S and 38°S over the continental shelf break and slope. Acoustic tracklines comprised an average of 780 nm of effort per survey. Hydrophone arrays (Auset®) were towed 150 and 300 m behind the vessel. The system was configured to give a variable frequency response from 1592 (High Pass Filter) to 100,000 Hz. Acoustic data were recorded as .wav files. Concurrent environmental and GPS data were logged automatically using WinCruz software. Visual positive identifications were associated to the acoustic recordings. The .wav files were analyzed using partially automated detections tools complemented with visual and acoustical searched for species confirmation whenever possible. A total of nine cetacean species were acoustically detected. The most frequently species were Physeter macrocephalus, Delphinus delphis, Stenella longirostris, Orcinus orca, and Globicephala sp.. Additional studies are needed to describe acoustic parameters of the various species present in this region in order to improve automated detection systems. [This study was supported by Instituto Aqualie and was funded by BG Group and Chevron Brasil Upstream Frade LTDA.]