A joint operation between two major reservoirs in the upper reaches of the Yangtze River has proven effective in creating favorable hydrological conditions for fish to spawn, according to the Changjiang Water Resources Commission.

The operation was conducted in the Three Gorges and Xiangjiaba reservoirs from May 27 to June 4, which is the regular spawning period for the black carp, grass carp, silver carp and bighead carp.

By increasing the water flow from the two reservoirs, the operation aimed to create a man-made flood process more favorable for the four species to breed.

On May 27, the average water flow from the Three Gorges Reservoir stood at 8,160 cubic meters per second. On average, water flow was increased by about 1,400 cubic m per second every day from May 28 to Saturday, bringing the maximum water flow from the reservoir to around 18,000 cubic m per second.

During the operation, Xiangjiaba, which is located upstream of the Three Gorges, saw water it discharged increase by 320 cubic m per second on average every day from May 29 to 31.

A preliminary estimate showed a total of roughly 46.1 billion fish eggs passed through a monitoring section in Changsha, capital of Hunan province, from May 27 to Sunday, a record high since 2011 when the operation was launched.