June 18th, 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.
“These whales depend, over the course of their lives, on a complex marine environment that is highly dynamic, and we expect the population to be resilient to that over time,” he said. “The most recent Unusual Mortality Event was much longer than the previous one from 1999 to 2000. The environment may now be changing at a pace or in ways that is testing the time-honored ability of the population to rapidly rebound while it adjusts to a new ecological regime.”
Researchers in Mexico reported numerous dead gray whales early this year in and around coastal lagoons. Females nurse their calves in these lagoons in winter before beginning their migration north to the Arctic each spring. They also reported few gray whale calves, suggesting that many female whales may not be finding enough food in the Arctic to reproduce.
So far this year, 47 gray whales have stranded dead on the U.S. West Coast, up from 31 last year and 44 in 2023, the last year of the UME. While some of the stranded whales appeared skinny or emaciated, others did not.
Tracking Reveals Change
The reduced abundance and calf count underscore the value of long-term monitoring in detecting trends, said Dr. Aimée Lang, a research scientist who helps lead the gray whale counts. A decade ago the eastern North Pacific gray whale population was a conservation success story, having recovered from commercial whaling and nearing all-time highs of 27,000 whales. NOAA Fisheries determined in 1994 that the species had fully recovered and no longer needed protection under the Endangered Species Act.
Today, however, the ongoing decline has scientists both puzzled and concerned. Ecosystem changes in the Arctic feeding areas the whales depend on to put on weight and maintain fitness are likely the root cause, Weller said.
The gray whale migration between Mexico and the Arctic crosses the California Current ecosystem and Arctic ecosystem. These areas have both experienced unpredictable changes in recent decades. “Certainly the whales are feeling that too, but may not be able to respond in ways that resemble those of the past,” Weller said. back...
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.
“These whales depend, over the course of their lives, on a complex marine environment that is highly dynamic, and we expect the population to be resilient to that over time,” he said. “The most recent Unusual Mortality Event was much longer than the previous one from 1999 to 2000. The environment may now be changing at a pace or in ways that is testing the time-honored ability of the population to rapidly rebound while it adjusts to a new ecological regime.”
Researchers in Mexico reported numerous dead gray whales early this year in and around coastal lagoons. Females nurse their calves in these lagoons in winter before beginning their migration north to the Arctic each spring. They also reported few gray whale calves, suggesting that many female whales may not be finding enough food in the Arctic to reproduce.
So far this year, 47 gray whales have stranded dead on the U.S. West Coast, up from 31 last year and 44 in 2023, the last year of the UME. While some of the stranded whales appeared skinny or emaciated, others did not.
Tracking Reveals Change
The reduced abundance and calf count underscore the value of long-term monitoring in detecting trends, said Dr. Aimée Lang, a research scientist who helps lead the gray whale counts. A decade ago the eastern North Pacific gray whale population was a conservation success story, having recovered from commercial whaling and nearing all-time highs of 27,000 whales. NOAA Fisheries determined in 1994 that the species had fully recovered and no longer needed protection under the Endangered Species Act.
Today, however, the ongoing decline has scientists both puzzled and concerned. Ecosystem changes in the Arctic feeding areas the whales depend on to put on weight and maintain fitness are likely the root cause, Weller said.
The gray whale migration between Mexico and the Arctic crosses the California Current ecosystem and Arctic ecosystem. These areas have both experienced unpredictable changes in recent decades. “Certainly the whales are feeling that too, but may not be able to respond in ways that resemble those of the past,” Weller said. back...
