Whale mortality rises in San Francisco Bay with 22 confirmed carcasses in 2025
Gray whale deaths in San Francisco Bay reached 22 as of mid-June 2025, with data showing continued population decline and signs of ecosystem stress and malnutrition.
Image credit: Copernicus EU/Sentinel-2, EO Broweser, The Watchers. Acquired on June 12, 2025
At least 22 whale carcasses have been confirmed in the San Francisco Bay Area so far in 2025, including 19 gray whales (Eschrichtius robustus), two unidentified baleen whales, and one minke whale. This is the highest number reported in the region since 2021, when an Unusual Mortality Event (UME) affected gray whales along the Eastern North Pacific.
Data collected by local observers and the Marine Mammal Center indicate that more than 30 gray whales have been seen alive in San Francisco Bay over the same period. This represents an increase from just 6 whales observed by May 2024.
Approximately one-third of those whales remained in the bay for more than 20 days, with visible signs of varied health that ranged from normal to emaciated condition.
The National Oceanic and Atmospheric Administration (NOAA) reported a total of 47 gray whale strandings along the U.S. West Coast by mid-June 2025. These include 27 in California, 13 in Washington, and 7 in Oregon.
NOAA had previously documented 690 strandings between December 2018 and November 2023 wherein the primary causes of the mortality were linked to malnutrition. Necropsies revealed that many whales had poor or depleted blubber reserves.
Factors contributing to nutritional stress included changes in Arctic feeding ecosystems, decreased prey availability, and increasing sea ice loss. Other possible contributing causes included vessel strikes and entanglement in fishing gear. Limited evidence of biotoxin exposure was also found.
Recent 2025 data suggests continued ecosystem stress. NOAA’s population estimate for the Eastern North Pacific gray whale stock showed a decline of approximately 45% from around 20 500 individuals in 2019 to 14 526 in 2023. Calf production also declined sharply, reaching a low of 217 in 2022 before slightly increasing to 412 in 2023. The last officially recorded count for Eastern North Pacific gray whales in 2024 was at 19 000.
Multiple cases in the San Francisco Bay involved trauma from vessel strikes, which remains a big risk in one of the world’s busiest port regions. NOAA is working with the U.S. Coast Guard, San Francisco Harbor Safety Committee, and ferry operators to implement mitigation strategies like vessel speed reductions, rerouting, and acoustic alert systems.
The current spike in whale deaths doesn’t appear to have a single clear cause. Changes in long-term migration patterns could also be drawing more gray whales into coastal and estuarine areas, where they may be more vulnerable. Field teams are still monitoring live whales in the bay and examining carcasses as they’re recovered.
References:
1 Nearly 2 dozen whales found dead around San Francisco Bay Area, alarming marine experts – Fox Weather – June 17, 2025
2 Gray whales along the West Coast appear to be in trouble – OPB – June 18, 2025
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