Detection and characterization of deep-sea fish vocalizations at the Atlantic Undersea Test and Evaluation Center

Deep-sea fish represent an understudied species due to the extreme physical conditions of their environment, including cold temperatures, darkness, and immense pressure. However, passive acoustic monitoring offers a unique opportunity to investigate these elusive species. This study builds upon previous research that identified possible deep-sea fish vocalizations at the Atlantic Undersea Test and Evaluation Center (AUTEC) in 2004, with no subsequent follow-up investigations conducted until now. A signal-to-noise ratio (SNR) threshold detector was developed to identify potential fish calls from hydrophone recordings. Audio files were decimated to 6 kHz and band-pass filtered (500–1500 Hz) to focus on frequencies of interest. Analysis of data from 2019 and 2023 revealed characteristic “growl-type” calls with distinct acoustic properties: duration of 0.88 ± 0.23 s, consisting of 35 ± 8 pulses, with individual pulse durations of 0.013 ± 0.004 s and inter-pulse intervals of 0.026 ± 0.006 s. This NUWC study resulted in 135 possible fish call detections. This research demonstrates the potential for passive acoustic monitoring to advance our understanding of deep-sea fish behavior and ecology in previously inaccessible marine environments.