Integrated model finds ENP grey whale abundance at ~16,000 and 32% decline since recent peak

Josh Stewart, an assistant professor with the Marine Mammal Institute, presented an integrated population dynamics model that synthesizes decades of abundance surveys, strandings, calf production and body condition. "We estimate the current population to be at about 16,000 whales," Stewart told attendees, adding that the integrated model constrains biologically implausible swings seen in single time series.

Stewart said the model shows a roughly 32% decline since the recent peak prior to 2019 and flagged a multi‑year reproductive depression and rising mortality rates that correspond with poorer body condition. He highlighted two environmental covariates with strong statistical links to carrying capacity: Arctic benthic prey biomass and days of access to feeding areas (sea‑ice mediated). Stewart and co‑presenters emphasized that human direct mortality (vessel strikes, entanglement) remained low relative to natural‑cause spikes recorded during mortality events.

The presentation underscored uncertainty around how much of the decline reflects true abundance loss versus changes in migratory behavior (some whales foraging at alternate sites and not passing traditional count stations). Stewart and other panelists recommended expanding covariates (for example, prey projections under warming scenarios and body‑length trends) and increasing coordinated tagging and cross‑region monitoring to reduce model uncertainty.