There are things we see on river trips, and there are things we see on ocean trips. River adventures normally involve rapids and canyons and the occasional big fish, and even large mammals, but not whales.

Whales are the stuff of oceans, right? Of course they are. So imagine the surprise recently when residents of the small port town of Astoria, Oregon discovered whales in the Columbia River. And these weren’t small ones either. These were humpback whales about 14 miles from the mouth of the river, reports CBS TV news affiliate KOIN 6.

The Columbia River here flows into the Pacific Ocean, creating one of the most dangerous bar crossings on the planet. Generally the ocean life does not mingle with the freshwater river life, but in this rare event the humpbacks were near the Astoria-Megler Bridge.

Beyond the surprise and delight, the question remains: How and why would these massive animals travel so far up river? Marine biologists point to a very strong temperature change in the water that is likely driving the whales’ food sources away.

“We have circumstances off shore that don’t favor whales very well this summer,” said Oregon State University Marine Mammal Institute Director Bruce Mate in an interview with the local CBS station. “It’s a very strong El Niño so the productivity is low and animals are seeking out resources where they can find them.”

Normally, humpback whales, which migrate up and down the coast of the western United States, can be found miles off shore. The whales in the river will likely return to the sea once their food supply dwindles.

Photo credit: Dreamstime