Why do fish sometimes jump out of the water?

At night, when we walk by the fish pond, we often hear “plop plop” sounds coming from the pond. Timid and superstitious people might think this is caused by water ghosts. In fact, this phenomenon also occurs during the day, but due to the noisy environment, people do not notice it. In the evening, when it is quiet, it is easier to hear this sound. This sound is produced by fish jumping out of the water.

Why do fish jump out of the water?

Fish jump out of the water because of insufficient air in the pond. They jump out to breathe oxygen from the air. This phenomenon is called fish “gasping,” which fishermen fear the most.

The “gasping” phenomenon is most likely to occur on winter nights and after thunderstorms in summer. Botanists tell us that green plants only release oxygen through photosynthesis in sunlight; at night, they also absorb oxygen. Aquatic plants similarly absorb some of the oxygen from the water at night, causing oxygen deficiency in the pond, prompting fish to jump out to breathe air. In cold weather, the oxidation and decomposition of organic matter in the water consume a large amount of oxygen; coupled with high fish density, the oxygen in the water is insufficient for the fish to survive through the winter. Additionally, water containing a lot of minerals and sulfides (rusty water) flowing from grasslands or mountains into the pond consumes oxygen through oxidation. If proper management is neglected, such as not checking in time and not taking effective measures like oxygenation and water injection, the “gasping” phenomenon will worsen, potentially leading to massive fish deaths. After summer thunderstorms, the water surface temperature is low while the bottom water temperature is high. When the warm water rises, the bottom humus is stirred up. At this time, on one hand, a large amount of oxygen is consumed to accelerate the decomposition of humus; on the other hand, a large amount of carbon dioxide is released. If effective measures are not taken in time, “gasping” will occur, and in severe cases, it can also cause fish deaths.