Understanding beaked whale summer distributions off the northeast United States through passive acoustics

Beaked whales are a cryptic family with limited behavioral and distributional data. Their long, deep-diving behavior limits their surface availability for observations. Passive acoustics have proven effective in detecting species-specific clicks during these deep dives, enabling continuous monitoring even under adverse conditions. In a 2021 (June–August) visual cetacean abundance survey off the Northeast region of the United States, passive acoustic data were collected using a towed hydrophone array. Active acoustic data were collected using shipboard echosounders, alternated systematically, to assess their impact on beaked whale passive acoustic detection. Species-specific frequency-modulated upsweep pulses from beaked whales were detected, classified, and localized using PAMGuard (v2.02.10), with individuals annotated by grouping click trains on consistent bearing changes. Data analysis using R (v4.3.2) and ArcGIS mapped distribution patterns, revealing three North Atlantic beaked whale species: Goose-beaked (Ziphius cavirostris), Sowerby’s (Mesoplodon bidens), and True’s (Mesoplodon mirus) beaked whales. Preliminary results indicate more detections occurred when the echosounder was off, consistent with past research. Species-specific distribution data in 2021 will be compared with the 2013 and 2016 abundance surveys. These results will improve our understanding of these cryptic species, contributing to the National Marine Fisheries Service’s stock assessments, and supporting conservation and management.