How can scientists tell how old animals are?

Question

For example, how do they know the Greenland shark is 512 years old (believed)?

In: Biology

Answer 1

For fish specifically, their age can be determined by counting growth rings in their bones. Bony fishes have a plate in their ear that makes a neat, concentric ring each year, like a tree. For sharks (which don’t have true bones) the vertebrae are used instead. Whale age can be determined by counting the layers in their earwax.