An Atlantic salmon's scales tell the story of its life - and even its ancestry and place of birth.
Growth rings on the scales tell the story of the salmon's growth, when it moved to salt water, and its return to fresh water after time at sea. The scales can tell us how many times the salmon has spawned, and can indicate the age.
Even growth rings can be an indication of Atlantic salmon raised in captivity, and whether the fish is an escaped farm-raised aquaculture salmon.
DNA, that can be extracted from the scales, can determine the relationship of that particular salmon to other groups of salmon, and ultimately can tell us from which stream, and even which section of stream the salmon came.