FRANCE: Salmon have ears. And they grow like trees.While salmon themselves use their ears for hearing and balance much the way humans do, scientists recently found a way to put this puzzling appendage to use for improving conservation strategies. By taking advantage of chemical traces in the tree-like growth patterns found in salmon ear bones, researchers can precisely trace a salmon’s life history, from the tiny tributary it was born in to the open ocean. The work was published today in the the journal Science Advances.Salmon ear bones, called otoliths, grow differently than the bones in your body do.
“It has rings that correspond to different times in a fish’s life,” lead study author Sean Brennan of the University of Washington said in an interview. “The inner rings correspond to the fish’s earlier life, and the outer rings correspond to progressively later times in the fish’s life.”
As the salmon swims about, its ear bone keeps growing and captures chemical traces from the environment within it. Since the ear bone is conveniently organized into chronological layers, scientists can get a sense of where the fish was at what time by slicing it open and comparing the different chemical traces found in different layers.
In this case, Brennan and his colleagues looked at the levels of different types of the element strontium in the ear bones. They mapped where these chemicals are found over a large area, and then matched the chemicals found in the ear bones to places on the map.
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