The behavior of gray whales in the San Francisco Bay is changing alarmingly. For years, seeing these cetaceans inside this bay was unusual, but things have changed drastically.
According to a study published on April 13, 2026, in Frontiers in Marine Science, from 2018 to 2025, 18.2% of the gray whales observed in the region died, many due to collisions with vessels.
These whales, which undertake extensive migrations from Baja California to the Arctic, rarely made stops in the San Francisco Bay. However, in 2025, 36 sightings were documented, often in large groups, raising concerns among scientists.
The researchers have collected images and data to create a catalog of 114 distinct whales that visited the bay since 2018.
Only eight of them belonged to subgroups that usually feed further south, indicating that the phenomenon is not limited to a few whales reusing the route.
Gray Whales
The Golden Gate Strait is a mandatory passage for whales entering and leaving the bay, sharing it with intense maritime traffic.
Josephine Slaathaug, the lead author of the study, warns that whales are difficult to detect, especially under fog, which contributes to accidents.
Among the examined bodies, 30 out of 70 showed injuries consistent with collisions. Additionally, internal necropsies on some specimens found trauma consistent with vessel strikes in 27 out of 45 cases.
Of the deaths whose cause could be determined, nine were attributed to collisions and two to malnutrition.
The decline of the gray whale population in the northeastern Pacific, reported by NOAA in 2025, adds pressure to the species.
Only 85 calves were observed in central California, the lowest number recorded, complicating their survival and reproduction due to food scarcity in the Arctic.
To mitigate the problem, initiatives like Whale Smart have been launched, led by The Marine Mammal Center and the San Francisco Harbor Safety Committee.
This program trains vessel operators to recognize and avoid whales, promoting temporary route changes and real-time communication through tools like WhaleAlert.
The study suggests implementing measures such as reduced speed zones and onboard observers to improve safety.
Although there are petitions to reduce speed in critical areas, adherence is limited and needs to improve significantly to be effective.
With climate change altering the migration patterns of whales, it is crucial to adapt our maritime transport routes.
Organizations like the Center for Biological Diversity and Friends of the Earth are taking this debate to the courts, seeking to review maritime routes based on their impact on marine life.
