Wild marine life will return to Dianshan Lake following a series of environmental protection projects that have been launched this year, city officials said yesterday.

A purse net covering 217 hectares has been removed from the lake, allowing fish, crabs and other life forms to return to eating plankton and other natural food in the lake.

The net was put in place in 2005 when fishing was banned on the lake in an attempt to recover its natural balance.

Local environment authority said fish foods put into the lake had deteriorated the water quality and made it difficult for the water to purify itself. If not controlled, the fish raising could have gradually endangered the tap water supply.

Dianshan Lake, located in Qingpu District, covers 62 square kilometers and has an average depth of two meters. More than 45 species of fish, shrimp, crabs and other life forms live in the lake.

"Those marine animals were restricted in the purse net before, so they could not live as other real wild animals, eating the natural food and drinking the water from the whole lake," said an official from the Qingpu district government.

According to the lake administration, a 15-square-kilometer wetland will be reconstructed around the Dalian Lake, which sits beside Dianshan lake, to soak up excess water that in turn controls flooding, as the two lakes are a major source for drinking water in the city.

The wetland is the final phase of environmental improvements around the lake, which is being overseen by East China Normal University.

Shanghai has 320,000 hectares of natural wetland and 370,000 hectares of artificial wetland, among which 215,000 hectares are at the mouth of the Yangtze River.