Is there anyway to tell how old a fish its?

Asphyx1a: Actually, one common way to estimate the age of a fish is by examining their otoliths or "ear stones". Otoliths are hard, calcium carbonate structures located behind the brain of fish. They grow layers of bone as the fish ages, similar to tree rings. By counting these rings, scientists can estimate a fish's age. However, it's not a foolproof method and does require the fish to be deceased. Also, it's worth mentioning not all fish species' age can be determined this way. It's more complicated for fishes that don't have hard structures that grow with age, or for the ones living in constant environment where seasons don't affect their growth.