Gray Whales Face Deadly Dangers in San Francisco Bay

New research reveals a high mortality rate for the massive marine mammals entering the busy waterway

Apr. 15, 2026 at 10:30pm by

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A bold, abstract painting in soft earth tones featuring sweeping geometric arcs, concentric circles, and precise botanical spirals, representing the delicate balance of the San Francisco Bay ecosystem and the challenges facing gray whales as they navigate the region's busy waterways.As gray whales face increasing threats from climate change and busy maritime traffic in the San Francisco Bay, a conceptual illustration captures the complex interplay of natural and man-made forces impacting these iconic marine mammals.San Francisco Today

A recent study found that nearly 18% of gray whales entering San Francisco Bay between 2018 and 2025 died, with at least 40% of those deaths caused by collisions with large vessels. Scientists warn that the true toll could be much higher, as many whale deaths go undocumented. Warming ocean conditions are disrupting the whales' food supply in the Arctic, pushing more of them to search for food in the bay, where they face the risk of deadly encounters with the region's busy maritime traffic.

Why it matters

Gray whale populations along North America's Pacific coast have already declined in recent years, and continued losses could slow recovery and disrupt ocean ecosystems that support fisheries and coastal health. Scientists and conservation groups are working to make these waters safer for the whales, but the challenge is significant given the bay's unique complexity and high volume of maritime traffic.

The details

The recent study found that nearly 18% of gray whales entering San Francisco Bay between 2018 and 2025 died, and at least 40% of those deaths were caused by collisions with large vessels. The researchers say these figures likely represent only a fraction of the reality, as many whale deaths go undocumented because carcasses never wash ashore. Last year, nearly two dozen whale carcasses were found in the region, and additional deaths have already been reported this season.

  • Between 2018 and 2025, nearly 18% of gray whales entering San Francisco Bay died.
  • In 2025, nearly two dozen whale carcasses were found in the region.
  • Additional whale deaths have already been reported in the current season.

The players

Josephine Slaathaug

The lead author of the recent study on gray whale deaths in San Francisco Bay.

Kathi George

The director of cetacean conservation biology at the Marine Mammal Center.

Rachel Rhodes

A scientist with the Benioff Ocean Science Laboratory.

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What they’re saying

“It's really important to understand that these are just minimums that we were fully able to confirm.”

— Josephine Slaathaug, Lead author of the study

“With climate change, there's less prey available to them in the Arctic. So whales aren't getting as much food as they need to survive these long migrations.”

— Kathi George, Director of cetacean conservation biology at the Marine Mammal Center

“It's such a uniquely complex and busy waterway. Then you add whales into the mix, and there's just not a lot of room to coexist.”

— Rachel Rhodes, Scientist with the Benioff Ocean Science Laboratory

What’s next

Scientists and conservation groups are working to make the San Francisco Bay waters safer for gray whales, with programs like Whale Safe using real-time tracking to alert ship captains when whales are nearby and initiatives like Blue Whales Blue Skies partnering with shipping companies to voluntarily reduce vessel speeds.

The takeaway

The high mortality rate of gray whales entering San Francisco Bay highlights the urgent need to address the threats posed by the region's busy maritime traffic and the impacts of climate change on the whales' food supply. Protecting these iconic marine mammals is crucial for the health of the broader ocean ecosystem.