Hundreds of dead fish were found floating at Dighalipukhuri in Guwahati on Sunday.
Assam Fishery department officials suspect the fish died due to depletion of oxygen level in the pond.
Preliminary investigation has ruled out poisoning, and environmental degradation is suspected to be the cause, an official said.
“Depletion in oxygen level in the water due to organic overload seems to be the reason behind the mass fish deaths, but we can confirm it only after a complete investigation,” the official said.
“The amount of dissolved oxygen in the water should be 5-10 TPM. But there is only 2 TPM of oxygen in the water of Dighalipukhuri.
SDRF personnel are now working to increase oxygen in the water
Dighalipukhuri, or ‘long pond’ in Assamese, is around 500 metres long and is located in the Ambari area of the state’s largest city.
Dighalipukhuri is one of the oldest tanks located at Ambari area in Guwahati .
Legend has it that Bhagadutta, who led the Kauravas in the Mahabharata, had dug the pond during the swayamvar of his daughter Bhanumati.
It derived its name from its length (dighal) and was hence called Dighalipukhuri.
It was originally connected to the Brahmaputra, and the Ahoms used it as a naval dockyard.
During the battles with the Mughals in Alaboi and Itakhuli (near Sukreshwar temple in present-day Guwahati), the dockyard at Dighalipukhuri served as a naval backbone.