A salmon can smell its way back to the exact stream where it hatched

In 1951, Arthur Hasler and Warren Wisby showed that young salmon imprint on the unique chemical scent of their home stream before heading out to sea. Years later, returning adults follow that memorized smell like a trail, tracing it through a maze of tributaries back to the very gravel bed where they were born.

— Arthur D. Hasler and Warren J. Wisby, Discrimination of stream odors by fishes and its relation to parent stream behavior — The American Naturalist, 1951