Mass fish death in Yamuna’s cleaner stretch raises alarms

Reports of possibly thousands of dead fish along the Yamuna near Burari in north Delhi since Wednesday night have raised concerns among activists and independent experts about the health of the river’s aquatic ecosystem

Reports of possibly thousands of dead fish along the Yamuna near Burari in north Delhi since Wednesday night have raised concerns among activists and independent experts about the health of the river’s aquatic ecosystem. The deaths have been reported in a stretch generally considered relatively cleaner than other parts of the river in Delhi and from where the Capital draws water for drinking.

Wildlife enthusiast and conservationist Hemant Garg, who spotted the dead fish on Wednesday night, said thousands had been seen upstream, extending to Shank numbers 10, 11 and 12. (HT)

A similar incident was reported near Burari in May 2025, when thousands of dead fish were seen floating in the river. Locals then alleged that chemical waste discharged from Haryana through canals had contributed to the deaths.

Wildlife enthusiast and conservationist Hemant Garg, who spotted the dead fish on Wednesday night, said thousands had been seen upstream, extending to Shank numbers 10, 11 and 12.

“We regularly go in Yamuna to wildlife conservation, bird census and tracking wildlife. The fish were observed last night and thousands of dead fish have been seen way upstream,” he said, adding that the water in this stretch is usually clean. “We should be wary as drinking water is also sourced from this part of river.”

Boatman Ranjan Mukhia said the water had developed a strong smell and the deaths were not confined to one stretch. Other boatmen upstream had also reported dead fish, he said, adding that carcasses had to be removed to prevent further deterioration in water quality.

Bhim Singh Rawat, a Yamuna activist and member of the South Asia Network on Dams, Rivers and People (SANDRP), said mass fish deaths are usually reported in summer, when high temperatures reduce dissolved oxygen in water.

“I can’t recall the last such episode in winter months. The possibility in this case could be untreated industrial effluents,” Rawat said, pointing to Drain 2 from Panipat, Drain 8 and a drain in Burari as possible sources of industrial discharge. He also said raw water flow in the river had remained low despite the monsoon.

Yamuna activist Pankaj Kumar said he had written to the Delhi Pollution Control Committee (DPCC), seeking urgent intervention. Mass fish mortality is a critical indicator of ecological stress, he said, citing low dissolved oxygen, high biochemical oxygen demand (BOD) and toxic industrial effluents as possible causes.

If toxic substances are present in quantities sufficient to kill fish, the water being drawn downstream at Wazirabad for drinking could pose a public health risk, Kumar said.

The New Delhi Nature Society said in a post on X that hundreds, possibly thousands, of fish were found dead near Burari on October 14. It said the cause had not been established, while noting local allegations of chemical waste discharged from Haryana and asking whether the deaths could be linked to acid rain on October 12.

Delhi has witnessed several similar incidents. In May 2026, hundreds of fish died at Sanjay Lake in east Delhi amid a heatwave and receding water levels. Experts pointed to high temperatures, concentrated pollutants and declining dissolved oxygen. In April 2026, thousands of dead fish surfaced in the Najafgarh drain, with locals suspecting industrial effluents from Haryana. Hundreds of dead fish were also reported along the Yamuna near Burari in July 2024 and May 2025.

The Yamuna’s monthly water quality report for September indicates that the river in Delhi showed no significant improvement despite the monsoon. A comparison with September 2025 showed higher biochemical oxygen demand and faecal coliform levels at several monitoring points.

At Palla, faecal coliform levels rose to 1,100 MPN/200 ml this year from 790 last year. At the ISBT bridge, they increased to 35,000 from 2,800. At Okhla barrage, levels reached 21,000, against 3,500 in September 2025. Faecal coliform indicates sewage contamination; the ideal level is below 500 units, with a maximum limit of 2,500.

At the ISBT bridge, BOD rose to 30 mg/l from 8 mg/l, while chemical oxygen demand (COD) increased to 92 mg/l from 44 mg/l. At ITO bridge, BOD climbed from 4 mg/l to 18 mg/l and COD from 20 mg/l to 60 mg/l. Faecal coliform levels there rose from 1,800 to 17,000 MPN/100 ml.

The prescribed bathing-water standards include BOD of 3 mg/l or less and dissolved oxygen of at least 5 mg/l. The reported deterioration adds to concerns about pollution in the river, although the cause of the latest fish deaths has not yet been established.