Year-round acoustic presence of fin whales southwest of Svalbard suggests mixed-use habitat for feeding and breeding.

Multiple lines of evidence indicate a northward expansion and year-round presence of fin whales especially around Svalbard, an area where highly variable Atlantic Water intrusion is changing the trophic community. Because fin whales are now documented in the high Arctic (≥ 80°N), we hypothesized that this would also increase their presence in lower latitude Arctic regions. We used one year of passive acoustic data collected on a mooring deployed on the continental slope southwest of Svalbard to assess the temporal acoustic presence of fin whales and the relationship with environmental data. Acoustic detections and call diversity were greatest in fall and spring and lowest in summer. The 20 Hz calls were present from July to April and the 130 Hz calls were present from August to April. Both calls peaked in September with smaller, secondary peaks in March. Downsweeps were bimodally present between July and October and between February and June. Linear models indicated more calls when krill and copepod numbers were high and sea ice extent and amphipod numbers were low. A year-round acoustic presence of a potential resident subpopulation of fin whales suggests the region is a mixed-use habitat for foraging and reproductive-related activities.