Gray Whales Face 18% Mortality in San Francisco Bay
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- Scientists from the Marine Mammal Center and California Academy of Sciences found that nearly 18% of gray whales identified in San Francisco Bay between 2018 and 2025 later died in the area, according to a study published in Frontiers in Marine Science.
- Boat strikes killed 30 of 70 gray whales found dead in the region during that period, with vessel trauma responsible for over 40% of strandings where a cause of death could be determined.
- Gray whales began appearing in San Francisco Bay only after 2018 as climate change disrupts their Arctic prey, and NOAA reports the broader population has dropped more than 50% since 2016.
- Researchers cataloged 114 individual whales in the Bay from 2018 to 2025, but only four were resighted in multiple years, suggesting most do not survive long enough to return.
- Malnutrition killed many of the remaining identifiable whales, and the study's authors raised the possibility that starving whales may lack the energy to dodge boats — linking the two leading causes of death.
- 2025 saw 36 gray whales enter the Bay, sometimes more than 10 at a time, prompting calls for ferry route changes, speed restrictions, and operator education programs to reduce vessel strikes.
Why it matters: With 36 whales entering the Bay in 2025 and boat strikes killing 30 of 70 dead whales found since 2018, the Golden Gate Strait bottleneck concentrates the entire problem in a single chokepoint where targeted interventions — speed limits and route changes that the study notes have already proven effective for large whales elsewhere — could be implemented by Bay Area regulators and commercial vessel operators.
