Autonomous towed hydrophone system detects many beaked whales and other cetacean species in waters of the Southern Ocean

A SoundTrap ST300HF hydrophone recorder in a streamlined, flooded towbody was towed behind expeditionary tourism vessels on trips to South Georgia and the South Sandwich Islands and to the Antarctic Peninsula in December 2019—February 2020. Recordings were analyzed to identify acoustic detections of cetacean species. Identified species included sperm whales (Physeter macrocephalus) and southern bottlenose whales (Hyperoodon planifrons). Acoustic detections also included echolocation pulses from several previously described beaked whale pulse types (BW37 and BW58) as well as a possibly new type of beaked whale echolocation pulse. Narrow-band high-frequency (NBHF) echolocation signals (typical of porpoises and some dolphin species) were detected at several locations, and one of these coincided with a sighting of hourglass dolphins (Lagenorhynchus cruciger). Unidentified large delphinids were also detected several times. This study shows the utility of a simple towed hydrophone system on a vessel of opportunity to study the distribution of cetaceans in rough seas that are difficult to study by visual survey methods. Additional research is needed to link the unidentified echolocation signals to known species throughout waters of the Southern Ocean.