Why are gray whales dying in San Francisco's waters? US scientists search for clues
Key Takeaways
- It has been reported that a record 21 dead eastern North Pacific gray whales were found in the broader San Francisco Bay in 2025; seven have died so far this year.
- Researchers link the strandings to dwindling Arctic prey, climate-driven shifts in migration, and an elevated risk of vessel strikes once whales enter the bay.
- A new study in Frontiers in Marine Science examined photos and necropsies (animal autopsies) and found a high rate of death among whales using the bay — offering both a conservation concern and a rare research opportunity.
- The phenomenon has implications for coastal communities, maritime operators and wildlife managers; potential responses include increased monitoring, reporting and targeted mitigation such as vessel slowdowns or reroutes.
What scientists have found
It has been reported that gray whales, which make the world's longest mammal migration (roughly 15,000–20,000 km roundtrip), are appearing in San Francisco Bay in greater numbers and earlier in the season than before. Josephine Slaathaug, lead author of a recent paper, says the species did not regularly stop in the bay prior to about 2018. The study examined hundreds of photographs and carcasses and concluded the bay now experiences “a very concerning high rate of death,” with many animals notably undernourished and some dying after vessel strikes.
Causes under investigation
Researchers point to a combination of ecological and human factors. Years of declining prey in Arctic feeding grounds — linked to climate change and shifting ocean conditions — appear to be leaving whales with reduced energy reserves, it has been reported that some are entering the bay driven by hunger. Necropsies (animal autopsies) and on-site observations suggest that while starvation-like conditions are present, direct human causes such as ship strikes are a frequent proximate cause of death for whales that become concentrated in the busy estuary.
Human impact and policy implications
San Francisco Bay is a working estuary with ports, ferries and recreational boating. More whales in the bay increase risks for both the animals and maritime traffic, and can affect workers in fisheries, shipping and tourism. For wildlife managers and policymakers the situation presents a narrow window to gather data on changing migration patterns and to consider mitigation — for example, enhanced monitoring, stricter reporting, voluntary or mandatory speed reductions in key areas, and temporary reroutes — though specific measures will require regulatory review and interagency coordination. For residents and mariners, authorities advise reporting sightings of distressed or dead whales to local stranding networks so necropsies and data collection can continue.
What does this mean for someone going through the immigration process right now? Practically none for immigration procedures — but coastal and port communities often include many immigrants and visa-holding workers whose jobs depend on safe maritime operations; changes to port practices or seasonal work patterns could indirectly affect employment. The broader takeaway: climate-driven ecological shifts are producing local consequences that touch livelihoods as well as wildlife.
Source: Original Article