Animal World

Fish, Amphibians, and Reptiles

How is the age of a fish determined?

One way to determine the age of a fish is by its scales, which have growth rings just as trees do. Scales have concentric bony ridges or “circuli,” which reflect the growth patterns of the individual fish. The portion of the scale that is embedded in the skin contains clusters of these ridges (called “annuli”); each cluster marks one year’s growth cycle.


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