Long-term passive acoustic monitoring captures spatiotemporal patterns of an elusive deep-diving predator across the eastern North Pacific

Understanding the spatiotemporal distribution of marine predators is necessary for ecosystem assessment and management, yet deep-diving predators such as beaked whales remain difficult to monitor due to their limited time at the surface. Passive acoustic monitoring offers a powerful complement to traditional visual surveys for these species, capturing presence continuously and independently of weather conditions or time of day. Here, we combine 12 years of passive acoustic monitoring across the eastern North Pacific with historical visual sighting records to characterize the spatiotemporal distribution of Baird's beaked whale ( Berardius bairdii ), a poorly understood deep-diving predator in the region. Long-term acoustic observations suggest a seasonal inshore-offshore migratory trend in the Gulf of Alaska and a latitudinal migratory trend off the US west coast, findings which were unobservable from long-term visual sightings due to logistical and seasonal constraints on effort. Interannual acoustic variability also suggests the influence of anomalous oceanographic conditions on Baird's beaked whale presence, particularly the coupled 2014–2016 marine heatwave and El Niño event. Together, acoustic and visual data provide a more complete picture of habitat use in this elusive predator than either method alone, highlighting the value of integrated long-term monitoring for managing vulnerable deep-diving species in a changing ocean.