Emerging Concern for Gray Whales in the Eastern North Pacific

For many decades now, it has been generally agreed that the gray whale population that migrates along the west coast of North America, between wintering areas in Mexico and summering areas in Canada, Alaska (USA), and northeastern Russia, represented a conservation “success” story. As described in the most recent (2018) IUCN Red List species assessment, the eastern North Pacific population had recovered strongly from past over-exploitation; the population increased by around 2.5% per year from 1968 through to a peak around 1987/88, after which the population declined, followed by a further recovery to an estimated 26,960 whales (95% confidence interval = 24,420-29,830) based on counts during the 2015/16 southbound migration off California. Unfortunately, things have not gone well since 2016.

Based on the most recent shore-based count during the southward migration between 31 December 2024 and 14 February 2025, scientists from the US National Oceanic and Atmospheric Administration (NOAA) estimated that the migratory population now “most likely” consists of only 11,700 to 14,500 individuals (https://repository.library.noaa.gov/view/noaa/70719). In other words, it has roughly halved since 2016. A June 2025 media release from NOAA revealed that only about 85 mother-calf pairs (95% CI = 55.48-293.5) migrated past the central California observation station between 31 March and 23 May 2025 on their way to feeding grounds in the Arctic. That was the lowest number since records began in 1994.

Calf production in this population has been unusually low since 2018-19 when a so-called “unusual mortality event” began. Between December 2018 and early November 2023, 690 gray whales were found stranded along the coasts of Mexico, the United States, and Canada. The causes of the low calf production and the 2018-2023 die-off are uncertain and this has caused growing concern.

Taken from the 2025 NOAA report on gray whales (Eguchi, Lang, and Weller, “Abundance of eastern North Pacific gray whales 2024/2025,” https://doi.org/10.25923/jqea-s505)

A recent paper on the recovery of baleen whale populations explores the possible links of downturns in abundance to changes in benthic prey availability, while an earlier paper underscored the capacity of gray whales to shift among various benthic and pelagic prey and presented evidence that whales in the eastern Chukchi Sea now routinely feed on krill. Eastern North Pacific gray whales may be an example of a population that is no longer being constrained from full recovery by commercial whaling but is limited in its growth and survival by modern-day threats that are even more challenging to tackle than commercial whaling was.

Gray whale body condition was assessed from aerial (drone) images obtained over multiple years in Laguna San Ignacio, B.C.S., Mexico, revealing large numbers of ‘skinny whales’ during years corresponding with unusual mortality events (UMEs) thought to be related to changes in prey availability. The percentage of “skinny” single whales (gray whales without calves) in “poor” condition peaked at 30% in 2020, declined to 4.6% in 2024 and then increased again to 13% in 2025. Photo credit: “Gray Whale Research in Mexico” team program, http://www.graywhaleresearchmexico.org

The CSG is being asked to reassess the eastern North Pacific gray whale population’s Red List status, and we are hoping to do that once the International Whaling Commission’s Scientific Committee has reviewed the new data and analyses and commented on how the latest findings should be interpreted.

References:

Eguchi, T., Lang, A. and Weller, D. (2005). Abundance of eastern North Pacific gray whales 2024/2025. https://doi.org/10.25923/jqea-s505

Martínez S.A., Swartz, S., Urbán, J.R., Lobo R.B., Díaz, F.C., Romero, A.V., Partida, E.R., Olguín, J.H., Rodríguez, F., and Nuñez, A.J. (2025). Informe de las actividades del monitoreo de la ballena gris (Eschrichtius robustus) temporada invernal 2025 en Laguna San Ignacio, B.C.S. México. https://www.graywhaleresearchmexico.org/updates/2025-annual-gray-whale-report-laguna-san-ignacio-and-bahia-magdalena