# Humpback whale sighting in California river delta

> Live situation record from CLSTR: https://clstr.news/situations/humpback-whale-sighting-in-california-river-delta
> Updated: 2026-09-22T17:21:56.000Z. Sources: 13. Developments: 2.

A humpback whale identified as ‘Rio’ (CRC-11620) made a rare appearance in California’s Sacramento River, traveling approximately 60 miles from its typical Pacific Ocean habitat. The whale was first spotted near the Rio Vista Bridge after entering the San Francisco Bay.

Researchers and the U.S. Coast Guard monitored the animal as it moved through the Carquinez Strait and Suisun Bay into the Sacramento-San Joaquin River Delta. While humpback whales are not adapted to freshwater, experts noted that similar incursions have occurred historically. Scientists remain uncertain whether the detour was due to navigation errors, injury, or illness.

Recent observations indicate the whale has begun heading west toward Port Chicago in Suisun Bay. The Marine Mammal Center has advised the public to maintain a distance of at least 100 feet to avoid influencing the whale’s course.

## Timeline

### 2026-09-22: Humpback whale Rio travels from San Francisco Bay into Sacramento River Delta

A humpback whale named Rio traveled from San Francisco Bay into the Sacramento-San Joaquin River Delta before heading back toward the ocean, prompting monitoring by marine mammal experts.

3 sources. https://clstr.news/cluster/humpback-whale-rio-travels-from-san-francisco-bay-into-sacramento-river-delta

### 2026-09-17: Humpback whale spotted in California's Sacramento River

A humpback whale named Rio was spotted in California's Sacramento River, roughly 60 miles from the Pacific Ocean, prompting scientific monitoring of the rare inland visitor.

10 sources. https://clstr.news/cluster/humpback-whale-spotted-in-sacramento-river-near-rio-vista

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Cite as: Humpback whale sighting in California river delta. CLSTR, https://clstr.news/situations/humpback-whale-sighting-in-california-river-delta