Did you know that fish have ear bones called otoliths. These bones not only aid in the fish’s balance but when sliced through, the age of the fish can be determined by counting the rows of concentric rings. This is just like a tree.
Often, when the fish is consumed by a predator species like seals, the ear bone is the only bone that doesn’t dissolve in the stomach acid of the animal. By collecting the scat of the seals and searching for these ear bones, scientists can determine what species of fish and the age of the fish that the seals are eating.