This is more of a biology question if you are curious about the anatomy of this type of fish. For the most part, these fish are typically going to live for right around three to four years. With that said, some of them will manage to breathe freshwater for right around eight years. As will be touched on later, adult crappies are going to be your main target if you want to eat them as they range anywhere from 10 to 20 inches long. Meanwhile, those that are only a few years old can be as small as four inches.