June 19, 2025 — The eastern North Pacific population of gray whales that migrates along the West Coast of the United States has continued to decline, with reproduction remaining very low. Two new Technical Memorandums from NOAA Fisheries’ Southwest Fisheries Science Center report the estimated population size and calf productivity in 2025.
The initial population estimate of gray whales, following an Unusual Mortality Event that ended in late 2023, suggested that their numbers may have begun to rebound last year. However, the most recent count from winter 2025 instead reveals a continuing decline. The new count estimates an abundance of about 13,000 gray whales, the lowest since the 1970s.
Only about 85 gray whale calves migrated past Central California on their way to feeding grounds in the Arctic earlier this year. That’s the lowest number since records began in 1994. Low calf numbers since 2019 indicate that reproduction has remained too low for the population to rebound.
The estimates are based on models that combine visual sightings from NOAA Fisheries research posts in Central California with assumptions about how the whales migrate. The assumptions create some margin for error, but the models indicate that in 2025 the population is most likely between 11,700 and 14,500. They indicate the number of calves produced was between 56 and 294.
The annual estimates are most valuable in revealing population trends over time rather than pinpointing the number of whales or calves in a given year, scientists said.
Past Resilience Wanes
Scientists attributed the Unusual Mortality Event from 2019 to 2023 to localized ecosystem changes that affected the Subarctic and Arctic feeding grounds. Most gray whales rely on prey in this region for energy to complete their 10,000-mile round-trip migration each year. The changes contributed to malnutrition, reduced birth rates, and increased mortality. Related research has linked fluctuations in the gray whale population to the availability of prey in its summer feeding grounds in the Arctic.
The gray whale population has proved resilient in the past, often rebounding quickly from downturns such as an earlier UME from 1999 to 2000. That makes the ongoing decline in abundance and reproduction following the more recent UME stand out, said Dr. David Weller, director of the Marine Mammal and Turtle Division at the Science Center and an authority on gray whales.