June 22, 2021

How do I know the age of the fish?

Many people like to raise fish. Some people will say that the fish you raise are very beautiful. How old are they? Although the fish that I have raised for several years are generally known to myself, many people do not know the true age of the fish. In fact, most of the fish’s age is also displayed on their own, and most of the fish’s body scales can indicate the fish’s age. Just like trees have growth rings, fish scales also have growth rings. But how do you tell the age of a fish by the growth rings on the scales? Let’s see if science will provide us with answers.

Most fish have small scales from birth, and these scales cover the outer layer of the skin layer by layer. The scales of most fish are bone scales evolved from the dermis. The position of the scales on the body of the fish is different, the size of the scales will be different, but most of the scales are similar in shape, like a cone with the top truncated. If you look closely at the scales alone, they are slightly thicker in the middle and thinner on the edges. The uppermost layer of scales is small and formed earlier in terms of time, while the area underneath is larger, which is also newly grown and younger.

The fish grow up year by year, and the scales are gradually increasing. Under normal circumstances, the temperature is suitable in spring and summer, and the food for fish is relatively sufficient, so spring and summer grow fast. In autumn, when the weather turns cooler and the water temperature drops, the growth of fish slows down, and basically no longer grows in winter. Periodic changes in nature will leave traces on living organisms. Tree rings are like this, and fish also leave the rings on their scales. Biologists call the ring that fish grow faster and wider as summer wheel, and the ring that grows slower and narrower is called winter wheel. One wide and one narrow represents one summer and one winter, that is, one year.

Generally speaking, fish scales can be observed relatively clearly under a microscope. If the conditions are not met, a magnifying glass can also see clearly. Take out one or several scales from the fish’s body. After careful observation, it is found that there is a black and white ring around the center like tree rings on the scales. These endless belts are also called growth belts. Count the turns of the black endless belt carefully. Under normal circumstances, the actual age of the fish is the number of circles of the black ring plus one. If you find five black bands on the scales of a fish, then the age of the fish is six years old.

In this way, the growth ring is suitable for most fish, but some fish do not have scales. At this time, we must start from other places. For example, the age of the flounder is estimated by the spine of the flounder, and the operculum of the salmon is used. Bone to calculate its age. The large and small yellow croaker we usually eat uses otoliths to calculate its age. Although the detection positions of these fish are different, these positions are all the same with concentric growth rings.

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