Thousands of dead fish have reportedly been spotted along the Yamuna near Burari in north Delhi since Wednesday night, raising concerns over water quality and possible industrial pollution. Wildlife experts and environmental activists have called for an urgent investigation into the incident.
Conservationist Hemant Garg, who spotted the dead fish on Wednesday, said large numbers had been observed upstream as well, extending towards Shankh numbers 10, 11 and 12. He warned that the incident required attention because the river is also a source of drinking water.
Ranjan Mukhia, a boatman in Burari, said the water had developed a strong stench and that fish deaths were not confined to the area. He added that boatmen upstream had reported similar incidents in Haryana and were removing carcasses to prevent further deterioration of water quality.
Industrial discharge suspected
Bhim Singh Rawat, a Yamuna activist and member of the South Asia Network on Dams, Rivers and People (SANDRP), said mass fish deaths are commonly reported during summer when high temperatures reduce dissolved oxygen levels. However, he noted that such incidents were unusual during the cooler months.
Rawat suggested that untreated industrial effluents could be responsible, pointing to possible discharges from Drain No. 2 in Panipat, Drain No. 8 and a drain in Burari. He also raised concerns about restricted river flow despite the monsoon season.
The precise cause of the fish deaths has not yet been established.
Yamuna activist Pankaj Kumar has written to the Delhi Pollution Control Committee (DPCC), seeking urgent intervention. He said mass fish mortality can indicate severe ecological stress caused by low dissolved oxygen, high biochemical oxygen demand (BOD) and toxic industrial effluents.
Kumar also warned that if toxic substances were present in sufficient concentrations to kill fish, water drawn downstream at Wazirabad for drinking purposes could pose a public health risk.
The New Delhi Nature Society, in a post on X, reported that hundreds or possibly thousands of fish had died near Burari on October 14. It cited local allegations of chemical waste entering the river from Haryana, while noting that the specific cause remained unconfirmed. The organisation also questioned whether the incident could be linked to acid rain reported on October 12.
Previous incidents raise alarm
The latest incident follows several episodes of fish mortality in Delhi’s water bodies. In May 2026, hundreds of fish died at Sanjay Lake in east Delhi amid a heatwave and declining water levels. Experts attributed the incident to a combination of high temperatures, concentrated pollutants and reduced dissolved oxygen.
In April 2026, thousands of dead fish surfaced in the Najafgarh drain, with residents suspecting industrial effluents from Haryana. Hundreds of dead fish were also reported along the Yamuna near Burari in May 2025 and July 2024.
Yamuna water quality deteriorates at several locations
The river’s pollution levels have also raised concerns. According to the September water quality report cited in the findings, the Delhi stretch of the Yamuna showed no significant improvement despite the monsoon.
A comparison of September 2025 and September 2026 data indicated substantial increases in faecal coliform and BOD levels at several monitoring locations.
At Palla, faecal coliform levels rose to 1,100 units, measured in MPN/200 ml, from 790 units a year earlier. At the ISBT Bridge, the level increased to 35,000 units from 2,800. At Okhla barrage, it reached 21,000 units, compared with 3,500 in September 2025.
Faecal coliform bacteria indicate possible contamination from sewage. The reported benchmark for the parameter is ideally below 500 units, with a maximum limit of 2,500 units, according to the figures provided.
At the ISBT Bridge, BOD increased to 30 mg/l from 8 mg/l recorded on September 3 last year, while chemical oxygen demand (COD) rose from 44 mg/l to 92 mg/l.
At ITO Bridge, BOD climbed from 4 mg/l to 18 mg/l, and COD increased from 20 mg/l to 60 mg/l. Faecal coliform levels also rose from 1,800 to 17,000 MPN/100 ml.
For bathing water, the specified benchmarks include a BOD level of 3 mg/l or less and dissolved oxygen of at least 5 mg/l.
The reported fish deaths have renewed calls for water sampling, identification of possible pollution sources and urgent measures to protect the Yamuna’s aquatic ecosystem and assess potential risks to downstream water users.
