Bowhead and beluga whale acoustic detections in the western Beaufort Sea 2008–2018

Abstract

The Distributed Biological Observatory (DBO) was established to detect environmental changes in the Pacific Arctic by regular monitoring of biophysical responses in each of 8 DBO regions. Here we examine the occurrence of bowhead and beluga whale vocalizations in the western Beaufort Sea acquired by acoustic instruments deployed from September 2008-July 2014 and September 2016-October 2018 to examine inter-annual variability of these Arctic endemic species in DBO Region 6. Acoustic data were collected on an oceanographic mooring deployed in the Beaufort shelfbreak jet at ~71.4°N, 152.0°W. Spectrograms of acoustic data files were visually examined for the presence or absence of known signals of bowhead and beluga whales. Weekly averages of whale occurrence were compared with outputs of zooplankton, temperature and sea ice from the BIOMAS model to determine if any of these variables influenced whale occurrence. In addition, the dates of acoustic whale passage in the spring and fall were compared to annual sea ice melt-out and freeze-up dates to examine changes in phenology. Neither bowhead nor beluga whale migration times changed significantly in spring, but bowhead whales migrated significantly later in fall from 2008–2018. There were no clear relationships between bowhead whales and the environmental variables, suggesting that the DBO 6 region is a migratory corridor, but not a feeding hotspot, for this species. Surprisingly, beluga whale acoustic presence was related to zooplankton biomass near the mooring, but this is unlikely to be a direct relationship: there are likely interactions of environmental drivers that result in higher occurrence of both modeled zooplankton and belugas in the DBO 6 region. The environmental triggers that drive the migratory phenology of the two Arctic endemic cetacean species likely extend from Bering Sea transport of heat, nutrients and plankton through the Chukchi and into the Beaufort Sea.

Sea ice directs changes in bowhead whale phenology through the Bering Strait

“…After 2017, bowhead whale southward passages through the Bering Strait were later than average, suggesting whales may be just starting to delay their arrival to wintering areas in the northwestern Bering Sea. Supporting evidence for this includes bowhead whale fall migration in the western Beaufort Sea occurred consistently later per season from 2008 to 2018, and that timing was influenced by the winter of 2016–2017 during which bowhead whales remained in the Beaufort Sea into mid-January of 2017 [ 61 ]. Additionally, bowhead whales were seen and heard in the Canadian Beaufort in the winter of 2018–2019 [ 20 ].…”

Monitoring Alaskan Arctic Shelf Ecosystems Through Collaborative Observation Networks

“…The WABC, a critical conduit of Pacific water, advects elevated concentrations of nutrients, chlorophyll, dissolved and particulate organic carbon, and zooplankton towards the Canadian Arctic Archipelago (Pickart et al, 2013). Bowhead and beluga whales congregate near the current along the outer shelf and continental slope of the Beaufort Sea (Stafford et al 2021). Due to wind-driven upwelling/ downwelling and hydrodynamic instability, the WABC fluxes a substantial fraction of its mass, heat, freshwater, and biogenic content offshore, impacting the Arctic interior water column, ice concentration, and ecosystem.…”

“…By deploying passive acoustic sensors on gliders and oceanographic moorings instrumented with other sensors, the relationship between top trophic level marine mammal occurrence and their environment can be elucidated (Stafford et al, 2021). The University of Washington has deployed acoustic sensors quasi-continuously year-round on oceanographic moorings since 2008 in the Bering Strait, Beaufort Sea, and Northern Chukchi Sea; since 2016 at the Chukchi Ecosystem Observatory; and since 2013 on gliders deployed from the Bering Strait moorings cruise for annual transits of the Chukchi shelf from Bering Strait to Barrow Canyon (Baumgartner et al, 2014).…”

“…Passive acoustic data have provided novel information on the migratory timing and presence of Arctic and subarctic species. For instance, bowhead and beluga whales have recently delayed their fall migrations out of the high Arctic (Hauser et al, 2017;Stafford et al, 2021), subarctic fin and killer whales are moving north and spending more time in an ice-free Chukchi Sea (Stafford, 2019;Escajeda et al, 2020), and critically endangered North Pacific right whales are being detected further north in the Bering Sea (Wright et al, 2019). The data provide baseline noise levels for evaluating acoustic environment changes caused by increased industrial and vessel traffic presence and climate changeinduced extension of the open-water season (Wright et al, 2018).…”

“…One means of assessing changes in the marine environment is to examine the distribution of flora and fauna that are directly influenced by environmental changes. In the Arctic, marine mammals and seabirds have been proposed as ecosystem sentinels of change (Moore and Kuletz, 2019), and passive acoustic sampling has proven to be a robust means of detecting speciesspecific presence of vocalizing marine mammals throughout the year (Stafford et al, 2021). Similar approaches are applied to planktonic, pelagic, and benthic communities resolved by timeseries sediment traps, water samplers, photographic and active acoustic imaging systems, nets, and benthic grabs, cores, and trawls (see citations later in the text).…”