They 'imprint' the chemical composition of the stretch of water where they hatch. Once they reach adulthood (after swimming in the oceans) they use this imprinted knowledge to 'home in' on the river where they hatched.
Exactly where they were born
exactly 2.09288277 ft.
Herman Salmon was born in 1913.
Isidore Salmon was born in 1876.
William Salmon was born in 1644.
David A. Salmon was born in 1879.
Eliza Salmon was born in 1787.
Margaret Salmon was born in 1975.
Nancy Salmon was born in 1906.
Roxroy Salmon was born in 1956.
Ross Salmon was born in 1964.
Robert Salmon was born in 1775.