Fish feel pain, but the degree of pain perception is different from that of humans. The animal has no cerebral cortex, so the process of feeling pain is much simpler. When they are stimulated by strong mechanical stimulation, nerves transmit signals to the brain to make decisions.
1. Vision: There are many kinds of fish. For fish living within 100 meters from the water surface, the retina contains a large number of cone cells, so they can sense visible light in the water. In fish living at depths of 100-1000 meters, retinal structure changes, reducing cone cells and increasing rod cells, so that they can feel the shape of objects in dark waters. Fish below 1600 meters have no cones, only rods, and their visual ability is weaker.
2. Hearing: From the appearance of fish, you can't see the ears, but fish are not without ears. On either side of the head is the inner ear, which is divided into two parts, the upper part is the elliptical bundle, and the lower part is the saccular sac. It can capture sound in water and transmit signals to the brain through chemical reactions. In addition, the inner ear can also be responsible for balance.
3. Olfaction: Fish live in water, so their sense of smell is different from that of terrestrial animals. The noses of terrestrial animals can capture volatile odors, while fish rely on amino acids in the water to identify the taste. From this, we can judge the water quality. At the same time, we can also find the fish around us, which can not only facilitate predation, but also avoid the invasion of natural enemies.
