Why are there fish in the cement pool where there is water for a long time on the mountain?

To build an artificial reservoir on a high mountain, water needs to be drawn from other places. There is no running water on the mountain, and it is probably water naturally stored in nature. Then these waters may contain aquatic plants and microorganisms, and there may be fish seeds and fry in them. Even if people don't pump water artificially, they only rely on rainwater to store water. When it rains heavily, there are streams, mud and the like rushing from other places, which are likely to contain fry and fish eggs. As the saying goes, "a thousand years of fish seeds, a thousand years of grass seeds." Fish eggs will be preserved in a specific environment for a long time without being destroyed and losing vitality. As long as they are in the right environment, they will erupt and become famous fish, and so will the fish in the cement pool on the mountain. Whether it is fish eggs brought by mountain springs or fish eggs stored in rain, fish eggs brought by rain erosion can play a role in making fish thrive. Grasshoppers will be found in dry land for a long time, and fish will be found in water quality for a long time. This is also a strange manifestation of the natural ecological chain, and the vitality of many creatures is beyond our phenomenon. People, animals and birds will unconsciously bring fish eggs from the waters where fish lay eggs to another water body! For example, washing your hands in the river, or walking in the water by the river, there may be some fertilized eggs of fish. When you go to the mountain again, you may come into contact with the water in the pool. Those fish eggs may fall into the pool, and then the fish eggs hatch, and there will be fish out of thin air in the pool. Similarly, other animals will "carry" fish eggs in this way.