Hello,
Signature just means distinctive. Distinctive means unique or peculiar. So, it's talking about the river's sediments, which is the special identifying mark for salmon's to go back to the Yukon.
Regards,
Andy
July 8, 2022
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It’s a particular quality that makes something different from other similar things.
July 10, 2022
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A mark of something. Andy said it best!
July 8, 2022
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