Why are gray whales dying in San Francisco's waters? US scientists search for clues

April 19, 2026

Eastern North Pacific gray whales have recently begun stopping in San Francisco Bay during their migration, a behavior not observed before 2018, likely due to declining prey availability in the Arctic caused by climate change. In 2025, a record 21 dead gray whales were discovered in the bay, with nearly one-fifth of whales entering the area now dying there, primarily from vessel strikes rather than starvation. The whales arriving are noticeably undernourished, predominantly adult and juvenile males lacking sufficient energy reserves to complete their Arctic migration.

Who is affected

Eastern North Pacific gray whales (specifically adult and juvenile males)
San Francisco Bay area residents and local communities
Researchers and scientists studying marine mammals (including Josephine Slaathaug, Kathi George, Moe Flannery, and their teams)
Ferry companies and commercial shipping operators in San Francisco Bay
US Coast Guard vessel traffic management
Army Corps of Engineers
Public marinas and port operations

What action is being taken

The Coast Guard and ferry companies have implemented safety measures for whale protection
Captains are being trained to give whales space, slow down, and report sightings
Researchers are conducting necropsies (animal autopsies) on dead whales
The Army Corps of Engineers is towing whale carcasses to secluded beaches for examination
Scientists are studying hundreds of photographs of whales and carcasses to understand mortality patterns
A coalition of industries is working with the Coast Guard to keep the harbor safe for whales and wildlife

Why it matters

This situation represents an immediate crisis for a species experiencing dramatic population decline, with numbers dropping by more than half since 2016. The whales serve as indicators of larger environmental changes occurring beneath the ocean's surface, particularly the impacts of climate change on Arctic prey availability and marine ecosystems. The emerging pattern of early-season sightings, low calf counts, and high human-caused mortality suggests the population may not recover as it has from previous declines, threatening the long-term survival of this species. Additionally, the presence of massive whale carcasses in busy shipping lanes creates immediate safety and logistical challenges for human maritime activities in one of the largest estuaries on the US west coast.

What's next

Gary Reed hopes to soon install an infrared camera on Angel Island to monitor whales surfacing at night and in high traffic areas
Scientists are looking for ways to find solutions to address the high rate of human-caused mortality
Researchers are working to make waters from Alaska to Mexico safer for whales
The published study serves as the first step in gathering science needed to inform conservation and management of the species

Read full article from source: BBC