A Chinook salmon cuts through the clear, cold waters of the Deschutes River of Central Oregon, his iridescent red scales glinting in the sunlight. And he’s not alone. He is just one of thousands of salmon returning to the spawning grounds where they were born. Today, Chinook are the largest living species within Oncorhynchus, the salmon genus, reaching up to five feet in length. But seven million years ago, a now-extinct species of salmon in the Pacific Northwest, O. rastrosus, would have dwarfed their modern relatives. The fish could grow…
