How do salmon find the exact river where they hatched?
A baby salmon hatches in a cold mountain stream, no bigger than your pinky finger. She spends her first year there, darting between stones, learning to catch bugs. Then one day she swims downstream, all the way to the ocean — thousands of miles away. She'll live there for years, growing huge and strong. But here's the wild part: when it's time to have babies of her own, she'll swim back upstream to the exact same stream where she was born. Not the river next door. Not close enough. The exact spot. How does she find her way home across an entire ocean?
Scientists used to think salmon navigated like sailors — by the sun and stars. But salmon swim deep underwater where you can't see the sky. Others guessed they followed ocean currents like highways. Nope. Salmon in different rivers swim completely different routes through the ocean, crisscrossing each other's paths. The real answer turned out to be much stranger: salmon remember the smell of their home stream.
