Temporal Trends in the Acoustic Occurrence of Baleen Whales in the Bay of Fundy, Canada: Observations from Passive Acoustic Monitoring

Kirsti A. Mrazek^1,* and Kalen E. Mawer¹

¹Eastern Charlotte Waterways, Inc., Blacks Harbour, NB E5H 1E5, Canada. *Corresponding author.

Northeastern Naturalist, Volume 32, Issue 1 (2025): 21–39

First published early online: 8 February 2025

Abstract
The outer Bay of Fundy supports 6 baleen whale species seasonally and year–round, but multi-species passive acoustic monitoring efforts are lacking in this region. This area also experiences significant activity from fishing, commercial shipping, and tourism, all of which contribute to underwater anthropogenic noise. We report on the minimum acoustic occurrence of baleen whales and ambient sound levels in the Bay of Fundy from a multi-year passive acoustic dataset. We took acoustic recordings opportunistically at 5 sites from 2015 to 2022 using a single archival bottom-mounted hydrophone and the bottom hydrophone from a 3-channel vertical array. We processed the data with automated detectors and manual validation to identify and confirm baleen whale vocalizations and calculated average ambient sound pressure levels as broadband and within the 100-Hz band level. Balaenoptera physalus (Fin Whale), Megaptera novaeangliae (Humpback Whale), and Eubalaena glacialis (North Atlantic Right Whale) were the predominant baleen whale species detected. Fin Whales were detected year–round, Humpback Whale detections peaked from July to October, and Right Whales were detected from July into October. Balaenoptera borealis (Sei Whale) were detected in June, July, and August in 2015, Balaenoptera acutorostrata (Minke Whale) were detected only minimally despite numerous visual sightings in this region, and no Balaenoptera musculus (Blue Whale) were detected. The Grand Manan site had the highest average broadband and band-level ambient sound-pressure levels. These observations highlight the area’s importance for baleen whales and contribute underwater soundscape data for past and future monitoring comparisons.

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