Chongqing - On August 30, a drizzle fell on Yinglonghu Reservoir in the Nan'an district. Wang Lixin, a boatman, and Fan Wancheng, the reservoir's manager, drove their patrol boat to the lake's center.

Autumn winds rippled across the lake's surface, and fish jumped out of the water from time to time, lovely and serene. As Fan Wancheng gazed at the scene in front of him, he couldn't help but sigh with relief, "Yinglong Lake Reservoir used to be eutrophicated (a form of water pollution), but now the lake is clear, and fish are swimming again! It's not easy."

According to Fan Wancheng, in recent years, the Yinglong Lake Reservoir has achieved both economic and ecological benefits by implementing the ecological breeding mode of "breeding fish with water and purifying water with fish."

Yinglong Lake Reservoir was officially put into service in 2008 and serves various purposes, including providing agricultural irrigation water and drinking water for people and livestock. With a total storage capacity of nearly 18 million cubic meters, water from the reservoir is primarily used for production and living in the four towns of Yinglong, Changsheng, Guangyang, Xiakou, and Chayuan New Town.

From then on, Fan Wancheng and Wang Lixin have been responsible for protecting the reservoir's ecological environment.

The reservoir's water quality was initially relatively good, but two years later, eutrophication began to occur.

According to Wancheng, many duckweeds, blue-green algae, and water hyacinth grew in the water, making it turbid. Because the water is a drinking source, chemicals cannot be used to remove the phytoplankton. Manual weeding is the only option. "At the peak, we weeded several tons of phytoplankton daily, but it didn't work very well. Phytoplankton will soon grow out again."

In 2011, Liangjiang Fishery, a subsidiary of Chongqing Water Conservancy Investment Group, improved the water quality of the Yinglong Lake Reservoir by implementing the ecological breeding mode of "raising fish with water and purifying water with fish." In this mode, juvenile fish are injected into the reservoir, where they consume plankton, algae, and aquatic plants in the water and serve as a means of controlling grass.

In those years, the bighead carp and silver carp juveniles were put in, then a batch of adult fish was caught every year, and then a batch of new juveniles was put in. As time passed, the water quality of the reservoir gradually improved. Breeding ecological fish in the reservoir differs from other breeding methods, which do not use fertilizer or medicine and rely primarily on fish that can purify water.

As a means of ecosystem protection, small reservoirs develop a large ecological fish industry. Chongqing has promoted ecological breeding in more than 70 reservoirs, producing more than 2.5 million kilograms of fish annually and selling well in the downtown area. As of now, Liangjiang Fishery is opening up the entire fishery industry chain - from the Fanjiaqiao juveniles breeding farm, the Yinglong Lake large-scale fish breeding farm, four regional transit bases, processing plants, and marketing network to the dining table in restaurants - to promote the brand of "Yuhu Lake Reservoir Fish."

"Our next step is to plant aquatic plants on the surface of Yinglong Lake Reservoir to absorb harmful substances in the water, create an ecological environment for fish to flourish, and diversify and enhance the reservoir ecosystem. It will improve both water quality and fish quality," said the person in charge of Liangjiang Fishery.

(Chen Qian, as an intern, also contributed to the report.)