"As I entered the water for a holy dip, I was put off by the stink of rotting fish all around," said a pilgrim from Gujarat, Pradeep Bhai.
An Uttar Pradesh Pollution Control Board official in Mathura said that untreated waste water and industrial effluents had been discharged upstream, resulting in the deaths of fish due to oxygen depletion.
Activists blamed the Okhla Barrage authorities for releasing untreated water without advance information.
In Vrindavan, thousands of fish were seen floating in the river.
"The whole area around Keshi Ghat visited by thousands of pilgrims daily is stinking and no one has come to clean up the area," complained Jagan Nath Poddar, convener of Friends of Vrindavan group.
In Agra, hundreds of activists joined the River Connect Campaign's river cleaning exercise on Sunday.
"We want people of Agra to participate in cleaning the river which is heavily polluted with reported mass fish deaths upstream of Agra," Devashish Bhattacharya, an environmentalist told IANS.
"All historical buildings are located along Yamuna's banks. If the Yamuna is sick and polluted, the architectural marvels like the Taj Mahal cannot remain unaffected," said Ranjan Sharma, an environmentalist.
Ahead of Diwali, which is falling on November 7, people usually clean up their homes but dump the garbage on the river bank which is already a victim of idol immersion activities, said Shravan Kumar Singh of the Braj Mandal Heritage Conservation Society.
"You cannot leave cleaning of public places to government employees. Each one has to be responsible for his share of garbage. People have to be taught to segregate and deposit the waste at the designated places," said one activist, Harendra Gupta.
(This story has not been edited by Business Standard staff and is auto-generated from a syndicated feed.)