Beluga dive behavior relative to fronts and stratified layers near Barrow Canyon, Alaska

Abstract

We report on the first beluga whale (Delphinapterus leucas), an adult female, from the Eastern Chukchi Sea (ECS) stock to be tagged with a Satellite Relay Data Logger (SRDL) that included a miniaturized Conductivity, Temperature, and Depth (CTD) sensor capable of collecting temperature (T) and salinity (S) profiles as the beluga dove. Prior work speculated that ECS belugas may target fronts and stratified regimes between water masses, because these boundaries may aggregate zooplankton, which in turn may attract fish that belugas prey upon. However, the SRDLs used in those studies were not capable of collecting CTD data necessary to identify water masses. The CTD-SRDL transmitted for 71 days, 8 July–17 September 2019, providing 492 time-depth profiles, indicating the shape and duration of beluga dives, and 255 CTD profiles, providing information on the location of water masses and ocean stratification used by the animal. We found that this beluga typically targeted fronts and stratified layers between water masses or colder water masses of Pacific origin. Of particular significance, we found that within the main summering area in Barrow Canyon, dives were co-located with the frontal zone between relatively warm and fresh Alaskan Coastal Water (derived from river discharge), and colder, saltier water of Pacific origin.