Humpback Whale ‘Rio’ Heads Back West Toward SF Bay After Ending Up In Sacramento River

A wayward humpback whale known as “Rio” is heading back toward the ocean after making its way inland from SF Bay into the Sacramento River last week, where its unusual detour drew crowds of excited onlookers.

The whale was first spotted in San Francisco Bay last Tuesday, heading east through the Carquinez Strait and into Suisun Bay before entering the Sacramento-San Joaquin River Delta. As SFGate reports, photos submitted to the Cascadia Research Collective helped the Marine Mammal Center identify the animal as Rio, a humpback that has been documented 15 times in California and Mexico over the past 24 years.

Rio then continued into the Sacramento River, where the US Coast Guard spotted the whale Wednesday. One witness told ABC10 that Rio surfaced roughly a block from Rio Vista City Hall, drawing people who had been following reports of the whale’s unusual journey.

“We came up from Concord because we heard about the whale last night on TV and we’re like, we have to see this thing,” said Katy Lee, speaking to ABC10.

Rio was then seen heading back west near Port Chicago in Suisun Bay Friday, according to an update from ABC10.

The Marine Mammal Center has reportedly been monitoring Rio, and they're asking people who encounter the whale to keep their distance. Boats and kayakers should stay at least 100 feet away and avoid influencing which direction the whale travels.

The whale’s activity is unusual, and experts say it could have been prompted by illness, injury, or poor navigation. SFGate notes that humpbacks are not adapted to freshwater, making prolonged travel away from the ocean potentially dangerous.

“While it’s unknown whether this whale is just passing through or if there is an underlying, unknown ailment, the best thing people can do is experience this adult whale’s presence from a respectful distance,” Kathi George, Director of Cetacean Conservation Biology at the Marine Mammal Center, said in a statement.

Although rare, humpbacks have made similar detours into the Sacramento-San Joaquin Delta and Sacramento River in the past. In 1985, a famous humpback named Humphrey traveled the same route into the Sacramento River before reaching a dead-end. Researchers eventually helped guide him back toward the Pacific, and his roughly 24-day trip inland reportedly remains the longest recorded such journey by a whale.

According to ABC10, two suspected humpbacks, believed to be a mother and calf, were also spotted near Rio Vista in 2007 before continuing into the West Sacramento deep water channel. Officials temporarily restricted personal watercraft access while marine mammal experts assessed the whales.

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