Why do fish "turn their white bellies" after death?

Why do fish "turn their white bellies" after death?

We have certainly seen such a phenomenon in life, if the fish dies, then it must be belly to the sky. And most fish belly color is relatively light, close to white, so people often say that the fish "turned white belly". So why do fish always have their stomachs up to the sky after they die?

In fact, after knowing that fish mainly rely on fish maws to regulate the rise and fall and balance of the body, it is not difficult to explain this problem. In most fish, there is an organ that regulates the specific gravity of the body, called a swim bladder. It can adjust the specific gravity of the body at different depths by deflation or inhalation, making it the same as the specific gravity of the surrounding water, so that the fish can stay in the water effortlessly. After the fish dies, this regulatory ability is naturally lost, and the swim bladder is full of gas, resulting in a decrease in the proportion of the body, so the fish will float to the surface when it dies. But why is the fish dead and not with its back to the sky? As long as you look closely at the body of the fish, you will understand, because the heaviest vertebrae grow on the back of the fish, and there are more muscles attached to it, and the proportion is naturally larger, while the abdomen is mostly an internal organ, the cavity is large, and the proportion is small, so after the fish dies, the abdomen with small weight is mostly upward.

There are other helpers with belly up, namely the swim bladder and fins. We already know that the swim bladder is mainly used to regulate the proportion of the body, while the fin is the main motor organ, and the fish swims in the water by the swing of the fin. But another function of these two organs is often overlooked, which is to maintain the balance of the body. Fish use swim bladders to regulate density when healthy, and use the nervous system to control the motor system to regulate posture. When a fish is injured or feels a lack of oxygen in the water, the nervous system loses control of the motor system, or the muscles are paralyzed, and the swim bladder and fins that maintain balance in the body can no longer function. With the help of the air-filled maw, the fish are more likely to float to the surface of the water, and the abdomen is facing upwards with a smaller proportion. This is also another reason for the "white belly" of fish after death.

。