Hundreds of fish jumping to the surface of Linh Dam Lake (Hanoi), what does it signal?

Recently, a clip was circulated on social media showing hundreds of fish jumping out of the water in Linh Dam Lake (Hoang Mai District, Hanoi). The clip was recorded by locals on the evening of September 18.

For many people, this is a strange phenomenon, witnessed for the first time. Therefore, most people wonder what causes the phenomenon of fish jumping out of the water? Some people are confused, asking if there is a problem with the water source in the lake? Or some people explain that it is due to the excessive growth of (harmful) algae in the lake, or heavy rain for many days reducing the oxygen concentration in the water, forcing the fish to jump up to find oxygen.

Regarding this phenomenon, sharing with Dan Viet newspaper, Mr. Kim Van Tieu, former Deputy Director of the National Agricultural Extension Center (Ministry of Agriculture and Rural Development) affirmed that the phenomenon of schools of fish jumping out of the water in Linh Dam Lake is just a normal phenomenon. Mr. Tieu said that the comments about the fish jumping due to lack of oxygen at the bottom, pollution, storms, etc. are all incorrect.

According to Mr. Tieu, at night, fish like light so they come to the surface and follow schools. When there is movement, fish jump up, this is a normal behavior of fish.

"Sometimes when we row our boat to an area with a lot of fish, they automatically jump out of the water. They sense it, so when one fish jumps, the whole school immediately follows," Mr. Tieu explained.

In many places, fish are trained to eat, and the school of fish will immediately jump out of the water when food is thrown up.

In fact, the phenomenon of fish jumping out of the water has happened before in China. The incident happened in August 2023, hundreds of fish suddenly jumped out of the water in Dien Tri Lake, Yunnan Province. The amazing scene was recorded by witnesses. This scene was shared on social media and attracted the attention of many people.

A series of fish continuously jumped out of the water, creating a scene that looked like a carp jumping over the Dragon Gate to become a dragon. This made the locals and tourists who witnessed it praise it endlessly. This scene looked like an extremely attractive performance.

Employees working at Dien Tri Lake said this was the first time they had witnessed such a strange sight.

Locals said the fish jumped to the surface of the lake and then more jumped when the boat moved. This strange scene is very similar to the image of carp jumping over the Dragon Gate, some even jumped onto nearby boats.

Ms. Tran Tinh, manager of a company that transports tourists by yacht on Dien Tri Lake, said: "The sight of fish jumping out of the lake is very rare. The reason for this phenomenon may be due to the recent heavy rains and lack of oxygen in the water, causing the fish to jump up."

Immediately after receiving information about the strange phenomenon, experts were present at Dien Tri Lake and are investigating the cause. Experts said that the fish jumping out of the lake were mainly silver carp.

Silver carp are freshwater fish. They are sensitive to changes in water currents and tend to live in schools. According to experts, heavy rains have occurred in Yunnan in recent days, causing an increase in the amount of water flowing into the lake. This may have stimulated the silver carp and caused them to jump. In addition, the frequent entry and exit of cruise ships to pick up and drop off tourists in the Dianchi Lake area has also caused disturbances in the water currents, affecting the fish's behavior.

Most recently, on June 24, 2023, a video recorded dozens of fish jumping out of the surface of a pond in a scenic area in Chengdu City, Sichuan Province (China). This strange scene lasted for 10 minutes.

On July 12, 2022, a similar scene occurred in Shandong when tourists were sitting on a boat around Tanning Lake. Hundreds of fish suddenly jumped out of the lake after a heavy rain.

Previously, in June 2020, in Nanjing City, Jiangsu Province, people walking around Xuanwu Lake saw hundreds of fish jumping out of the water. Many people said that the fish jumped as if they wanted to gasp for air.

Why do fish jump out of water?

According to the Vietnamese Women's Newspaper, in this case, the fish jumped out of the water or suddenly flipped over due to a lack of oxygen at the bottom. When the water quality changes suddenly or even the water temperature is clearly stratified, the fish will feel a certain "restlessness" and stress, if the situation is serious, they will jump up.

On hot days, when air pressure causes the amount of dissolved oxygen (an extremely important factor for aquatic life) in the water to decrease sharply, freshwater fish compete to jump out of the water. They do this to absorb dissolved oxygen in the middle and upper water layers.

There is also another reason. On windy days, the amount of dissolved oxygen in the water also increases. Too much oxygen also stimulates the fish in deep water to jump around. Due to being too excited, these fish will compete to jump out of the water. This phenomenon can occur in reservoirs with large water surface areas.

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