Dozens of tons of dead fish that have washed up in Hanoi’s West Lake were likely killed by a lack of oxygen, said the city’s government.
In a statement, the city strongly warned the public against eating the dead fish until the cause of their deaths is ascertained.
Some of the dead fish have been sent for testing and the results should provide conclusive evidence, environmental authorities said, without indicating when the results would be released.
Fish were found floating all over the 500-hectare (1,235-acre) West Lake, with locals first coming across them last Friday night, said Pham Van Dong, an executive for the West Lake Environment Company, which is in charge of cleaning up rubbish from the lake.
Dong said the die-off was “unprecedented” and “abnormal”, and that “it was a significant number”.
“This is the most severe fish die-off ever,” said Dong.
According to West Lake’s management board, it is estimated that 4,000 cubic meters of untreated wastewater is discharged into the lake everyday by households, restaurants and hotels on the banks.
Preliminary water samples have shown that ammonia concentrations are three times higher than the standards set by environmental authorities.
The fish die-off has local people wondering if something or someone had poisoned the water, while tourists have complained about the foul smell, calling it the "Dead Fish Lake”.
“The first thing that hits you is the smell of dead fish. You then see the amount of dead fish everywhere and they are dying in shoals, it's odd,” said a British tourist on social platform TripAdvisor.
The dead fish include carp and perch.
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