Bowhead whale acoustic occurrence and vocal behavior in central Fram Strait

Passive acoustic monitoring enables data collection on marine mammals over large temporal and spatial scales and in remote areas such as the Arctic Ocean. Passive acoustic data are collected at different recording sites in eastern and central Fram Strait since 2012, contributing to the Arctic Observatory FRAM (FRontiers in Arctic Marine Monitoring). Here, data recorded at 78°50 N, 0°E from July to November 2012 were analyzed for the daily acoustic presence of marine mammals. Bowhead whales (Balaena mysticetus) were acoustically present during 12 days in October and during 16 days in November, but acoustically absent from July to September. Downsweep song (three types) was present both in October and November, while upsweep song (one type) was only present in October. Besides bowhead whales, blue whales (Balaenoptera musculus), fin whales (B. physalus), narwhals (Monodon monoceros), sperm whales (Physeter macrocephalus) and harp seals (Pagophilus groenlandicus) were recorded. Acoustic species interactions regarding the overlap of species-specific sounds in time and frequency range were explored. In this context, temporal and spectral overlap of biophonic (blue and fin whale vocalizations) and anthrophonic (airgun) signals were detected in the low-frequency (<100 Hz) spectrum. Our results emphasize the importance of Fram Strait as marine mammal habitat, possibly providing (summer) feeding opportunities for blue and fin whales and an overwintering ground for bowhead whales and narwhals. Understanding the spatio-temporal patterns in the distribution and acoustic behavior of marine mammals considerably benefits the development of effective conservation and management strategies for critical habitats in the Arctic Ocean.