An annual three-month fishing ban on the middle and lower reaches of China's Yangtze River came into effect Wednesday amid signs it might be helping to preserve fish stocks after seven years.

Staff members of the fishery department get ready to patrol at the estuary of Yangtze River in Shanghai, east China, on April 1, 2009. Officers of the Administrative Committee of Yangtze River's Fishery Resources will collaborate with colleagues in charge of the fishery department of cities along the Yangtze River, to curb illegal fishing activity during the three-month fishing ban starting from April 1. [Pei Xin/Xinhua]

The ban would be lifted on June 30, said Hu Xuedong, deputy director of China Fishery Administration Commanding Center.

"The fast developing economy has damaged the environment of the river. Many species have been dying," Hu said.

"The ban aims to improve the ecological environment and it has been effective," he said.

The ban stretches along 120 kilometers of the river, covering 10 cities and provinces, including Shanghai, Jiangsu, Anhui, Jiangxi and Hubei.

Inspection teams would travel to tributary rivers and the Three Gorges area, Hu said.

A fishing ban on 110 kilometers of the upper reaches of the Yangtze River started on Feb. 1 and will run until April 30.

The bans would affect about 3,000 fishermen and 1,280 fishing boats on the river itself and cover more than 100 varieties of fish.

The seasonal ban, in place since 2002, was also considered crucial to sustain the fishery resources in the freshwater Dongting Lake in central China's Hunan Province.

The lake, covering 2,740 square kilometers, is home to 119 varieties of fish, including some rare species, supporting almost 10,000 fishermen.

Another 122-day ban began on March 1 in China's largest freshwater lake Poyang Lake in east China's Jiangxi Province.

Poyang Lake covers 3,583 square kilometers and has an annual average water depth of 8.4 meters. It is a home to 140 varieties of fish and around 600 other animals.

About 100,000 fishermen living in the area were ordered to dock their vessels, as the lake's annual fishing season came to a close.