Beluga whales in the western Beaufort Sea: Current state of knowledge on timing, distribution, habitat use and environmental drivers

Abstract

The seasonal and geographic patterns in the distribution, residency, and density of two populations (Chukchi and Beaufort) of beluga whales (Delphinapterus leucas) were 2 examined using data from aerial surveys, passive acoustic recordings, and satellite telemetry to better understand this arctic species in the oceanographically complex and changing western Beaufort Sea. An aerial survey data-based model of beluga density highlights the Beaufort Sea slope as important habitat for belugas, with westerly regions becoming more important as summer progresses into fall. The Barrow Canyon region always had the highest relative densities of belugas from July-October. Passive acoustic data showed that beluga whales occupied the Beaufort slope and Beaufort Sea from early April until early November and passed each hydrophone location in three broad pulses during this time. These pulses likely represent the migrations of the two beluga populations: the first pulse in spring being from Beaufort animals, the second spring pulse Chukchi belugas, with the third, fall pulse a combination of both populations. Coreuse and home range analyses of satellite-tagged belugas showed similar use of habitats as the aerial survey data, but also showed that it is predominantly the Chukchi population of belugas that uses the western Beaufort, with the exception of September when both populations overlap. Finally, an examination of these beluga datasets in the context of wind-driven changes in the local currents and water masses suggests that belugas are highly capable of adapting to oceanographic changes that may drive the distribution of their prey.

Decadal shifts in autumn migration timing by Pacific Arctic beluga whales are related to delayed annual sea ice formation

“…Passive acoustics relies on belugas vocalizing in close proximity to hydrophones (~5–15 km), and we could not ascertain population identity from vocalizations. However, the Beaufort Sea hydrophone was placed near a Chukchi beluga summer–fall core area (Hauser et al ., ), and previous work supports our assumption that vocalizations after September would specifically detect Chukchi belugas (Garland et al ., ; Richard et al ., ; Stafford et al ., in press, Suydam et al ., ). Both populations transit near the Bering Strait hydrophone in autumn (Hauser et al ., ; Citta et al ., ), in contrast, so we expect both populations were acoustically detected and examined median passage dates accordingly.…”

“…S2). It is not currently possible to determine population identity from vocalizations (but see Garland et al ., ), but we could assume beluga vocalizations observed after September at the Beaufort Sea location were characteristic of Chukchi belugas based on previous studies (Richard et al ., ; Suydam et al ., ; Hauser et al ., ; Garland et al ., ; Stafford et al ., in press). We focused on the far right tail of the cumulative distribution of calling days to determine final migration date of Chukchi belugas out of the Beaufort Sea.…”

Habitat selection by two beluga whale populations in the Chukchi and Beaufort seas

“…Other environmental changes in the Pacific Arctic are associated with sea ice loss, such as increasing wind and storms that affect primary and secondary productivity [ 69 ], which may affect beluga prey. Belugas seem relatively responsive to changing conditions [ 86 ], yet further research is needed to clarify the effects of diminishing sea ice and to examine broader long-term impacts for each population. Ultimately, our results provide a benchmark by which to assess future changes in beluga habitat use and help guide regional development of offshore areas.…”

Seasonal variation of the Beaufort shelfbreak jet and its relationship to Arctic cetacean occurrence

“…The peaks in beluga occurrence in May and July represent differences in the migratory timing in spring/summer of the two different populations of this species, the Beaufort Sea population (April–May) and Eastern Chukchi Sea population (July–August). The peak in October is presumed to represent the westward migration of Eastern Chukchi Sea whales [ Stafford et al ., ]. As was the case for the bowheads, the enhanced upwelling in the month of October is likely to bring prey‐rich waters toward the boundary, in this case Arctic cod which feed on the zooplankton.…”