The ear bones of Chinook salmon develop a unique chemical signature that allow researchers track the fish's movement, a new study from the University of Washington finds.
Researchers say that the bone, known as an otolith, develops the same chemical signature as the water in which the fish swims. They compare the bone's signature to a tree's growth rings.
"Each fish has this little recorder, and we can reveal the whole life history of the fish from the perspective of the otolith. Each growth ring is a direct reflection of the environment the fish was swimming in at the time it was formed," said study lead author Sean Brennan.
The chemical signature reflects the amount of the trace element strontium found in the water. Strontium is gradually released into streams as moving water erodes bedrock, and eventually makes its way into the fish. The amount of strontium in the water varies significantly by location, making it a "strong" indicator of each fish's movement.
Researchers hope that their findings can help them explain dwindling chinook salmon population.
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