Acoustic density estimation of North Atlantic right whales (Eubalaena glacialis) in Cape Cod Bay, MA, USA

With fewer than 400 individuals remaining, critically endangered North Atlantic right whales ( Eubalaena glacialis; NARWs) embody New England’s foremost marine conservation challenge. In spring, a large portion of the NARW population visits Cape Cod Bay (CCB), MA, USA, a critical foraging area. Traditionally, aerial surveys have documented the abundance and distribution of NARWs in CCB. In this work, we employ passive acoustic monitoring to accomplish this task. This method offers a cost-effective and largely automated approach toward improved temporal resolution of observations. Regularly and universally produced by NARWs of all ages and sexes, the upcall vocalization serves as a proxy for NARW presence. This contact call’s highly stereotyped signal structure renders it optimal for detection through machine learning. From February to May 2019, five marine autonomous recording units (MARUs) continuously monitored the underwater soundscape in CCB. Manual upcall annotations across 20 days were used to evaluate a NARW automatic detector that ran over the full recording duration. Multiple arrivals across the MARUs were then matched through time-difference-of-arrival association. After estimating population-level calling rates, NARW density in CCB was calculated across the season. Results will be compared to visual survey observations conducted by the Center for Coastal Studies.