Chemical tags in ear bones track Alaska’s Bristol Bay salmon

An otolith is pulled out from inside the brain cavity of a Chinook salmon.

Scientists from Aquatic and Fishery Sciences and other institutions are learning a lot about where Chinook salmon swim in Alaska’s Bristol Bay region through chemical signatures recorded in their ear bones. Similar to a tree’s growth rings, this bone—called an otolith—accumulates layers as the fish grows. Acting as a little recorder, each layer of the otolith corresponds to the unique chemical signatures of the waters in which they swam. This information essentially tracks a fish’s movements, and can play an important role in mapping the most productive environments—this not only helps scientists understand fish ecology better, but has implications for their conservation as well.