Can you tell the age of a fish by the size of its gills?

The size of a fish's gills cannot be used to accurately determine its age. While the size of a fish's gills does change as it grows, it is influenced by many factors, such as water temperature, oxygen levels, and the species of fish.

Instead, fish age is typically determined by examining their otoliths, which are small, calcified structures in the inner ear that grow in rings, much like the rings of a tree. These rings can be counted to estimate the age of the fish.

If you want to estimate the age of a fish without killing it, you can use a non-lethal method called scale aging. This involves removing a few scales from the fish, and examining them under a microscope. Like otoliths, fish scales grow in rings that can be counted to estimate the fish's age.