Why are there fish in the pool formed by rain?

The first possibility is that the soil in that pit already has fish eggs. There have been traces of fish around the pit that may have been built before, leaving fish eggs in the soil. You should know that fish seeds will not be destroyed even for hundreds or thousands of years, because there is a film around the fish seeds to protect them, so the fish seeds have strong viability. When fish seeds meet the appropriate environmental temperature, they will break the membrane and hatch into small fry. After a while, there will be fish in the pond. This possibility is still very large, and most fish are produced because of this.

The second possibility is that some fish eggs refined by fish will be taken away by birds and taken to other places, just falling into these small ponds. Under the right circumstances, it will become a small fish, and gradually, there will be many fish in the pond. Waterbirds, such as swans and cormorants, fish in the water, during which fish eggs may stick to their feet and feathers. As waterfowl move between different water bodies, fish eggs in one water body may be brought to another water body, and these fish eggs will gradually hatch into fish in the new water body. So after a pond is dug up, it is likely that waterfowl or other aquatic insects brought fish eggs into the pond, so that fish will appear.

It is also possible that fish or fish eggs will reach the pond along the current when the pond is connected with other water bodies during the period of heavy rain and rising water. Another rare situation is that the fish in the pond are blown away by the wind. Because of the waterspout, this will cause the fish to be blown into the sky, and the "Yu Yu" will drop.