Over the past two days, tens of thousands of fish have died in the Nhieu Loc-Thi Nghe Canal after heavy rain. Around 14 tons of fish of multiple species have been collected by employees of the HCMC Urban Environment Co. Ltd from a three-km section of the canal flowing between Districts 3 and Tan Binh.

Vo Thi Mong Thu, head of the HCMC Fisheries Department, said unseasonal rain has caused toxic gas accumulated underneath the mud to be released into the canal, killing the fish. The sheer amount of trash in sewers that got washed into the canal might have also reduced oxygen levels in the water, also contributing to the fish’s death, she added.

"We are looking for a way to reduce the fish population and treat the water to prevent such situations in the future," she said.

However, the Nhieu Loc-Thi Nghe Canal isn’t the only place where dead fish were found after the heavy rains. They were also found in several lakes in HCMC.

On Monday morning, personnel of the An Lac Ward People’s Committee managed to remove around 500 kg of dead fish from a 5,000-square-meter lake near the Ehome 3 residential area of Binh Tan District.

Nguyen Huy Hoang, who lives in an apartment block in the area, said the fish had died en masse following a heavy rain two nights earlier.

"My house is located near the top of the building, and yet the stench was unbearable. The other night, the wind brought the smell in and it was impossible to sleep," he said.

To Hoang Giang, chairman of the An Lac Ward People’s Committee, said the lake has been around for nearly a decade and is privately owned as part of the district’s park. Fish dying inside the lake isn’t a rare occurrence, but it has never happened in such large numbers, he said.

HCMC is no stranger to the phenomenon of fish dying after heavy rains, especially at the beginning of the year. In 2016, around 70 tons of dead fish were found in the Nhieu Loc Canal, prompting authorities to use 20 tons of chemicals to treat the water.