At least 400 dead fish were on Sunday found floating in a Guwahati tank, said to have a Mahabharata link.
Joggers around the city’s iconic Dighalipukhuri, meaning “long pond”, detected the fish floating and brought it to the notice of the local authorities.
Minister for Fisheries Parimal Suklabaidya said the Department officials ascertained the cause behind the mass deaths of the fish. The dead fish weighed about 600 kg.
“The fish mortality was due to sudden dip in oxygen level and high organic load in the tank. Department officers, after examination, found the death of fish not due to poisoning but environmental degradation,” he said, adding that water was showered over the tank as a short-term measure with pumps to increase the oxygen level.
Jayaditya Purkayastha, an aquatic animal specialist, who has been working on turtle conservation across Guwahati’s ponds, said the local authorities should resume paddle boat service as a practice without any passengers and spank the water with bamboo to increase the dissolved oxygen (DO) in the tank.
“DO is one of the most important factors for the maintenance of biodiversity in a pond. Our atmosphere has about 20% oxygen or 2,00,000 parts per million (ppm) but only about 1,00,000 ppm gets dissolved in water. DO concentration below 3ppm will kill fish,” he said.
Non-penetration of sunlight due to a layer of algae has also been a factor behind the fish death. “Boating and spanking the water prevents surface algae from accumulating,” he said.
Dighalipukhuri, about 500 m long, is associated with the legend of local king Bhagadatta, who fought for the Kauravas in the battle of Kurukshetra. One of his elephants was named Ashwatthama. It is said that Bhagadatta had dug the pond during the swayamvar of his daughter Bhanumati.
