The only real way to tell the fishes age is to remove the otoliths (ear bones) and count the number of rings on it (like a tree). Most of the time we crack the otoliths in half and look at the exposed surface under a dissecting microscope. If it is stunted the rings will be supper close together and hard to count without the aid of a microscope. If this is a public lake, I would call your local Fisheries biologist who manages the lake and ask him to age a few fish for you. Who knows, they may already have this info.
In a lake with normal growth in the south, the fish in your picture should be 1 year old based off its size.
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