What I learned on a field trip

My DD's school went to the Warm Springs Dam Fish Hatchery today and one of the things I learned was that fish are born with all the scales they are ever going to have, and they are a lot like tree rings–you can see a ring for each season they have lived, and are wider when they grow more, like in the summer.

From the Texas Parks and Wildlife site:

"Fish with bones have scales. Some fish, such as gar, have heavy, plate-like scales called ganoid scales. Other fish have thinner scales. Fish scales form rings as they grow. During the cold months, scales grow more slowly and leave a ring on the scale. Like rings on a tree, you can count rings on a scale for clues on the age of fish. This is easier to do with fish that live where winter temperatures are cooler. Fish without scales include catfish, sharks, most eels, lampreys and rays."

That's funny, 'cause when I have a really good growing season, my scales reflect it, too!