HANGZHOU, June 6 (Xinhua) -- Over 5 billion fry were released into China's waters on Tuesday, as the country marked national fish releasing day.

More than 1 million fry of important economic species such as silver fish and bighead carp were released into Qiandao Lake in east China's Zhejiang Province.

Zhang Chuanqiang, deputy head of Chun'an County, where the lake is located said silver fish and bighead carp eat 30 to 40 kilograms of algae to grow by one kilogram. That removes nitrogen and phosphorus from the water, curbing eutrophication and blue algal blooms and improving water quality.

The lake covers 573 square kilometers, and is home to 114 known fish species, with an economic value of over 4 billion yuan (600 million U.S. dollars).

In Fuzhou City of east China's Fujian Province, some 150 million fry were released, including silver carp, grass carp and Japanese eel.

Yu Kangzhen, Vice Minister of Agriculture, said releasing fish fry on a large scale can improve water quality and help the recovery of fishery resources.

Since 2011, the country has spent around 4 billion yuan releasing more than 120 billion fish fry.

It is estimated that some 64.5 percent of the fish caught in inland waters are from the releases. For every one yuan spent on fry, 8.85 yuan of fish can be caught as a result.