Ever wondered how salmon navigate across thousands of miles of ocean without getting lost? After years feeding at sea, the fish swim through vast expanses of featureless water back to the rivers where they hatched. Now scientists may have finally answered a mystery that has baffled them for decades, after finding evidence suggesting salmon use the Earth’s magnetic field to guide them back to their spawning grounds. Researchers believe that when the fish first enter the sea, they memorise the location’s magnetic field and use it as a home address. The magnetic field varies across the globe, allowing animals to use it as a ‘map’ and determine their location.
Since the earth's magnetic field is constantly undergoing minor shifts and variations, scientists correlated the preferred route of the salmon with the magnetic field data from the same year the fish went to sea.
What they found was that salmon tended to choose their route around Vancouver Island based on the distinct magnetic signature of the river when they first went to sea two years earlier.
Prety cool stuff. But I always just assumed the salmon used GPS like the rest of us. Doesn't everyone?