Guwahati,  Ecological degradation, leading to depletion of dissolved oxygen level in a pond in Guwahati, has claimed the lives of hundreds of fish, Assam Fisheries Minister Parimal Suklabaidya said on Sunday.

Around 400 fish species weighing around 600 kg were found dead in the Dighalipukhuri tank in Guwahati since Saturday night and the minister has directed Fisheries Department officials to visit the site and ascertain the exact cause of the mass death.

An official statement said that officials, after examination of the collected samples of the dead fish and the water body, found that dissolved oxygen depletion in the tank, coupled with high organic load, were the causes behind the deaths of fish.

"Fish mortality was due to sudden dip in oxygen level and high organic load in the tank. Departmental officers after examination found deaths of fish not due to poisoning but environmental degradation," Suklabaidya said in a tweet.

The department, as a short term measure, increased the oxygen level in water by showering water through pump and creating wave action through mechanised boats, the statement said.

The centuries-old Dighalipukhuri pond, which is more than 500 metres long, has boating facilities and is a popular tourist spot in Assam's main city of Guwahati.