How do researchers determine the age of fish?

The oldest known fish in the world is a shark; no scales. Its age was estimated by the eyes.

I always understood it to be eyes and answer Includes eyes. rubbish.

I’ve done aging with otoliths before. You need to magnify them to count the rings and it can be rather difficult sometimes. Of course there’s different sizes otoliths depending on the size of the fish you’re trying to age. Definitely takes practice to get good at it.

Scales seem to be an acceptable answer, but apparently ears should have been a choice & a better answer, ie the otoliths of the inner ear.

Scales appear to be an acceptable answer, but ears

cut it in half and count the rings

Figured scales because trees are aged by the rings.

I think (and the explanation backs it up) that it is eyes and/or scales depending on the species. So eyes is as correct as scales.

Scientists also take a small bone from the ear, put it on a microscope and look at all the circles that it has, and that shows the age of the fish.

rayvan, No. Like counting the rings of a tree.

how long has that logic been around??