The whale binaural rings experiment: Long-range acoustic monitoring of North Atlantic right whales in the Gulf of St. Lawrence.

Effective real-time monitoring of baleen whales over broad areas was assessed using two 20-m circular hydrophone arrays designed for detecting and localizing North Atlantic right whale (NARW) upcalls. The system was deployed over a 24-d period in August 2021 to monitor a ∼80-km-wide trough heavily frequented by NARWs in the Gulf of St. Lawrence. Key functional parameters throughout the processing chain were estimated from in situ conditions and integrated with numerical simulations. The spatiotemporal performances of the system-using deep-learning neural networks upcall detection and bearing-crossing localization-under in situ noise levels was consistent with predictions from comprehensive acoustic modelling of the full transmission pathway, from source emission to signal reception. Among the 3117 NARW upcalls detected, 30% were successfully localized within the common detection area shared by the two hydrophone arrays. Significant diel changes in call occurrence rates were observed. Spatiotemporal call patterns reveal multi-scale habitat use across the 3600-km2 surveyed region. This study highlights the enhanced capabilities and operational constraints of this beamformed, high-gain, directional listening system relative to conventional single-hydrophone passive acoustic monitoring approaches, particularly under conditions of elevated anthropogenic noise.