And through some little thread, a few molecules of stone from where you began, you begin following and finding your way. Our female Snake River salmon, who has traveled thousands of miles, knows how to head toward home. Her genetic clock has told her it's time. After her second or third winter in the ocean, she's come in to feed near the coast. And then it seems her incredible sense of smell takes over.
Scientists say freshwater plumes from the great rivers can go hundreds of miles out to sea.
And so it may be that our female chinook, swimming through such a plume, can detect the differences in salinity and temperature. Can essentially sniff her home river. So she heads toward it, toward the memory of the smells of her youth and all that awaits her. And then when you're coming home, it's not only that you're going to give all and die to get there. You may not get there.