MOSCOW, Idaho (AP) — Researchers at the University of Idaho are looking at the ear bones of salmon to help discover just how close the fish get to returning to the spawning beds where they emerged as fry.

The ear bones of salmon are made up of thin layers and a new layer gets added every day, similar to tree rings. The composition of each layer changes based on the temperature and chemistry of the surrounding water. UI College of Natural Resources Associate Professor Brian Kennedy told the Lewiston Tribune he can track the fish's migratory history by analyzing the layers.

A study by Kennedy and others last year showed 55 percent of Chinook salmon studied returned to within a kilometer of where they were spawned, while 87 percent came within 10 kilometers.