A herring has only one herring core. Fish shock stone, also known as fish stone, is the most abundant in herring, also known as herring stone. It grows under the occipital bone of herring and is used for keratin hyperplasia caused by crushing hard objects. Herring stone is not a stone, its main component is keratin, which looks a bit like jade and amber, just the result of keratin proliferation. Black herring and grass carp have different draughts. It can eat snails, mussels, clams and so on. Most of these aquatic creatures have hard shells. In order to eat these things smoothly, the teeth of black herring should be chewed hard. After a long time, hyperplasia will form above the teeth, and hard-shell food will be easy to chew.