Description: Underwater sound is ubiquitous throughout the world’s oceans. Evaluating its impact and relevance for the marine fauna is highly complex and hampered by a paucity of data, lack of understanding and ambiguity of terms. When comparing sound (an energetic pollutant) with substantial pollutants (chemical, biological or marine litter) two notable differences emerge: Firstly, while sound propagates instantaneously away from the source, it also ceases immediately within minutes of shutting off the source. Anthropogenic noise is hence per-se ephemeral, lending itself to a set of in-situ mitigation strategies unsuitable for mitigation of persistent pollutants. Secondly, while pollution with hazardous substances can readily be described quantitatively with few parameters (environmental concentration as the most important one), the description of sound and its impact on aquatic life is of much higher complexity, as to be evidenced by the issues multifaceted description following hereinafter.

Description: New developments and applications of autonomous Passive Acoustic Monitoring (PAM) technology in polar regions have come at time of increased interest in the Arctic and Antarctic due to predictions of global climate change. Information gained with autonomous PAM systems has provided new information on polar pinniped communication, mating systems, distribution, and the relationships between these species and their environment. Although new discoveries continue to be made, there is still much that remains to be learned about these species. This chapter is organized into a review of species specifi c information known prior to 2000, case studies describing new knowledge gained through the use of autonomous PAM systems since 2000, and future projection on how autonomous PAM systems can be used to address and fi ll data gaps related to polar pinnipeds.

Description: 〈jats:p〉Bowhead whales (〈jats:italic〉Balaena mysticetus〈/jats:italic〉) of the East Greenland-Svalbard-Barents Sea (Spitsbergen) population are still considered endangered, but knowledge on spatio-temporal distribution patterns and behavioral aspects remains scarce, yet crucial for this population’s conservation. Long-term passive acoustic recordings were collected at five locations in central and eastern Fram Strait (78-79°N, 0-7°E) as part of the Ocean Observing System FRAM (Frontiers in Arctic Marine Monitoring). Data recorded in 2012 and 2016/2017 were analyzed for the acoustic occurrence of bowhead whales at hourly resolution using a combination of automated and manual analyses. Bowhead whales were acoustically present from autumn throughout the winter months (October-February) and occasionally in spring (March-June), supporting hypotheses that Fram Strait is an important overwintering area. Acoustic presence peaked between mid-November and mid-December with bowhead whale calls recorded almost daily, often hourly for several consecutive days. The observed peak in acoustic presence coincided with the presumed mating period of bowhead whales, starting in late winter, indicating that Fram Strait may also serve as a mating area. Detailed analyses of recordings of a single year and location revealed eight distinct bowhead whale song types, comprising simple songs and call sequences. No bowhead whales were recorded in summer (July-September), indicating that they had migrated to summering areas or resided outside the detection range. Compared to previous studies in western Fram Strait, bowhead whale detections in our recordings were less frequent and recorded songs were less complex. The observed regional differences in bowhead whale acoustic behavior across Fram Strait suggest that eastern Fram Strait may represent a less favorable part of the bowhead whale overwintering area.〈/jats:p〉