People often see a few small stones in the head of yellow croaker when cooking especially when frying small croaker, it looks white and especially hard, people may ask, is this stone? Is the fish accidentally eaten in?

In fact, the two small stones in the yellow croaker's head are called "otoliths", which are located in the ball sac of the inner ear of the fish's head, and are mainly composed of calcium carbonate, which plays a role in balance and hearing. When the yellow croaker swims in the sea, once the sound waves from the outside world reach the fish body, it senses them because of the stimulation of the otoliths and sensory cells. The otoliths also press on the sensory cells to bring its out-of-balance body into alignment, keeping the fish in balance.

The otoliths are not formed after the fish swallows the stone, they are originally in the yellowtail's ears. Scientists pay more special attention to the otoliths of fish, and they can determine the species of fish according to the look of their otoliths; they can also grind the fish's otoliths into thin slices, and deduce the age of the fish from the circles of lines on them.

In the 1970s and 1980s people used to catch yellow croaker by playing drums on boats. It's where the vibrating waves of sound vibrate this tiny stone on the fish's head so that the fish gets dizzy! So the number of croaker declined greatly in those years.

Scientists have found that yellow croaker are not the only fish with otoliths, many animals have them, but the otoliths are larger in the family Staphylinidae, to which the yellow croaker and dorado belong, so they are easier for us to spot. Other fish have smaller otoliths, which are usually invisible without attention, but their otoliths play a similar role to that of the yellow croaker.