A humpback whale was spotted near the Rio Vista Bridge after traveling through San Francisco Bay, the Carquinez Strait and into the Sacramento Delta.
RIO VISTA, Calif. — A humpback whale was spotted in the Sacramento River near the Rio Vista Bridge on Wednesday, bringing an unusual visitor to local waters. The sighting is the latest in a history of whales making their way into Northern California waterways.
Giancarlo Rulli, Associate Director of Public Relations at the Marine Mammal Center, said the whale was last spotted near Rio Vista on Wednesday, but no sightings have been reported yet on Thursday. The whale entered San Francisco Bay on Tuesday and traveled east through the Bay, Carquinez Strait and into the Sacramento-San Joaquin Delta.
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Rulli said the whale has been identified as CRC-11620 through Cascadia Research Collective’s photo-identification catalog. The Marine Mammal Center is monitoring the situation and coordinating with partners for future visual assessment and monitoring.
Kathi George, Director of Cetacean Conservation Biology at The Marine Mammal Center, said the whale is out of its normal habitat area, and it’s unknown whether the whale is just passing through or has an underlying health issue.
The Marine Mammal Center urges the public to avoid changing the whale’s course and let it decide where it wants to go. People who encounter the whale should stay at least 100 yards away per the National Oceanic and Atmospheric Administration’s guidelines, use binoculars or a telephoto lens rather than approaching.
CRC-11620 has been documented 15 times over the past 24 years in California and Mexico, according to Rulli. Its first recorded sighting was off California in 2002, and its most recent sighting before this week was in Baja California in February 2026.
While whale sightings in the Sacramento Delta and Sacramento River are unusual, they are not unprecedented. Over the years, several whales have traveled far inland through the waterways connecting the Pacific Ocean to the Sacramento region.
Here’s a look at some of the notable whale sightings in local waters:
1985: Humphrey, a 45-foot, 40-ton humpback whale, swam from San Francisco Bay through the Carquinez Strait and into the Sacramento River. He passed under the Rio Vista Bridge and ended up in a dead-end slough about 69 miles from the ocean. Researchers eventually guided him back toward the Pacific using a flotilla of boats and whale-feeding sounds.
1990: Humphrey returned to the San Francisco Bay and became stranded on a mud flat near Candlestick Point. After three days of work, the Coast Guard and marine mammal experts were able to free him and tow him back to sea.
2007: Two whales believed to be humpbacks were spotted near Rio Vista before making their way into the West Sacramento deep water channel. Officials restricted personal watercraft access while marine mammal experts assessed the whales and worked on a plan to guide them back toward the ocean. Officials were also concerned one of the whales appeared to be tangled in fishing line.
Recent years: A whale was also spotted in the Carquinez Strait, another waterway connecting the Bay Area to the Sacramento Delta.
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