Hanoi announces causes of mass fish deaths after months of investigation

Fish gone belly up draw flies on West Lake in October. Photo by VnExpress/Ngoc Thanh

Fish have been floating belly-up in a number of the capital's lakes this year.

Pollution and changes in the weather were the main causes behind a series of mass fish deaths in Hanoi's lakes this year, according to the city’s People’s Committee.

The committee said that weather changes had led to a lack of oxygen in the water that suffocated the fish. In addition, domestic wastewater and rubbish had affected the aquatic environment.

In October, 200 tons of dead fish washed up in West Lake, the city's largest lake, followed by thousands of dead fish in Linh Dam Lake.

Other incidents were also reported at Van Quan, Ngoc Khanh and Hoang Cau.

Hanoi has over 100 ponds and lakes scattered across the city, but many of them are polluted by sewage and rubbish.

Research conducted from 2011-2016 by Hanoi’s Center of Environmental Monitoring and Analysis revealed that most heavy metals in water samples exceeded permitted levels.

“Only iron met the required standards; other metals like lead, copper and mercury exceeded the limit,” the report said.

The city hopes to resolve the problem with a $726 million sewage treatment plant.

Construction began in early October and is scheduled to finish in three years. The system is designed to treat 270,000 cubic meters of sewage every day by collecting waste along the Lu, To Lich and Nhue rivers.