These marine mammals are trading ocean waves for river systems in record numbers.

Picture a California sea lion basking on a dock in San Francisco Bay. Now imagine that same sleek marine mammal lounging beside a freshwater river 150 miles from the nearest ocean. This isn’t some fever dream or maritime tall tale—it’s becoming the new reality across the American West.
From the Columbia River to California’s Central Valley, sea lions are venturing deeper into inland waterways than ever before. Marine biologists are scrambling to understand why these typically coastal creatures are abandoning their saltwater homes for lengthy freshwater adventures that would have seemed impossible just decades ago.



