How salmon find their way back to their birthplace to reproduce after migrating across thousands of miles of open ocean has mystified scientists for more than a century. But now marine biologists at think they may have discovered the secret.

The earth’s magnetic field varies across the globe, with every oceanic region having a slightly different magnetic signature. At the beginning of their lives, salmon may read the magnetic field of their home area and ?imprint? on it. By noting the unique ?magnetic address? of their birthplace and remembering it, the fish may be able to distinguish this location from all others when they are fully grown and ready to return years later to lay their eggs.
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