Wind-driven movement ecology of blue whales detected by acoustic vector sensing

Endangered blue whales in the eastern North Pacific seasonally occupy essential foraging habitat in Monterey Bay National Marine Sanctuary (MBNMS) off central California. Acoustic vector sensing within MBNMS, together with biologging and ecosystem observations, is revealing blue whale movement ecology across a range of temporal scales. Over days to months, blue whales were observed to repeatedly track wind-driven upwelling plumes within which their essential prey—krill—form dense aggregations. Over the years, blue whales predominantly occupied shelf-slope habitats, however, exceptionally strong upwelling was associated with a shift to greater occupancy of offshore deep-water habitats. The strongest upwelling year exhibited higher abundances of krill and greater offshore reach of coastal upwelling plume habitat. At both time scales, these acoustically detected behavioral patterns within the regional blue whale population are consistent with behaviors of individual whales revealed by biologging. Supporting the recovery of endangered whale populations requires understanding where, when and how they live, and how risks from human activities intersect. Biologging and periodic visual monitoring are essential to understanding the spatiotemporal patterns of whale habitat occupancy and movement ecology, and these patterns can be resolved in greater detail and with greater persistence through continuous acoustic monitoring of highly soniferous species.