This recently released study on westslope cutthroat trout migration tracking is pretty interesting stuff . . .
Like a tree’s concentric growth rings, a small bone within a fish’s ear reveals a history of its growth. And according to a new study of westslope cutthroat trout in the Flathead River system, the bone also contains a record of its migration pathways – a kind of geochemical diary of its life.
The bone, called an otolith, acquires a new ring every day of the fish’s life. All fish have them, and for decades scientists have counted the bands of the bone to determine the age of a fish, as well as estimate population growth.
But a study published last week by a slate of Montana researchers in the Canadian Journal of Fisheries and Aquatic Sciences brings to light new information that the ear bones also contain a unique fingerprint of the water chemistry where the fish swims on a given day, which can be used to map the entire life history of a fish within a river network.