Insights into the migratory patterns and seasonal distribution of one of the world’s rarest whales, the North Pacific right whale

• Main Author: Wright, Dana Louise
• Other Authors: Read, Andrew
• Format: Doctoral or Postdoctoral Thesis
• Language: unknown
• Published: 2023
• Subjects: Conservation biology; Bering Sea; distribution; Eubalaena japonica; right whale; stable isotope ecology; zooplankton; Bering Shelf; Pacific; Calanus glacialis; North Pacific right whale; Sea ice
• Online Access: https://hdl.handle.net/10161/29118

Dissertation The eastern North Pacific right whale (NPRW; Eubalaena japonica) is one of the world’s rarest large whales, with fewer than 35 animals remaining. Foundational data on the distribution and biology of this species is lacking, hampering effective monitoring and conservation. In this dissertation, I used disparate ecological approaches – food web modeling and stable isotope analysis– to broaden our understanding of the distribution and trophic ecology of this rare whale. The right whale’s primary forging ground on the highly productive Southeastern Bering Sea shelf is experiencing a rapid decline in seasonal sea ice extent. Annual fall surveys of zooplankton in this region provides a data-rich resource to explore relationships between shifting environmental and right whale prey – the zooplankton genera Calanus, Neocalanus, and Thysanoessa. The results of these surveys have been used extensively in prior research to study zooplankton dynamics, but few studies have incorporated species interactions. I created a discrete-time Bayesian biophysical food web model of the Bering shelf zooplankton community to jointly model relationships between environmental covariates and individual zooplankton species during a warming period on the shelf (1996-2016). This model framework allowed me to quantify the contribution of density independence and density dependence to zooplankton community dynamics. Similar to the results of prior research, I found that sea ice dynamics drove density-independent growth across zooplankton species, but species interactions contributed only minimally to community dynamics. My results suggest that the presumed preferred prey of right whales, Calanus glacialis, will shift north with the decreasing sea ice cover to stay in cold bottom water conditions. Next, I used carbon and nitrogen stable isotope values in NPRW skin and baleen to study the distribution and foraging ecology of North Pacific right whales. Whale skin provides a seasonal snapshot of the whale's ecology (weeks to months ...