|A dead fish floats in Deepor Beel. Picture by Kishore Talukdar
Borjhar, Oct. 18: The Assam fisheries department has found that low oxygen levels in the water caused the deaths of fishes in Deepor Beel, a Ramsar site, in the past week.
The level of dissolved oxygen in the water was found to be below 3mg per litre as opposed to the required 4mg and more in a litre.
“Aquatic life is adversely affected if the oxygen level falls below 3mg milligram per litre. The matter is serious,” a fisheries department source said.
More than 1,00 fishes had been found floating in the wetland in the past week.
Sources said adequate dissolved oxygen is necessary for all forms of life. Natural stream purification processes require adequate oxygen levels in order to provide for aerobic life forms.
“The release of sewage into the water might have caused the fall in oxygen levels,” Pranjal Sarma, the sub-divisional fisheries development officer, Guwahati, said, adding that results of more tests are awaited.
The local residents alleged that sewage enters the wetland through the Bahini and Bharalu rivers.
Sources said large-scale encroachment, heavy siltation from the hills surrounding the beel, accumulation of waste from the Bharalu and Bahini rivers, unregulated fishing practices, quarrying within the beel ecosystem and other reasons have pushed this once-pristine ecosystem to the brink of disappearance.
“Decomposition of excessive aquatic vegetation, including eyraleferox, a favourite food of wild elephants, might also reduce the oxygen level in autumn,” said professor M.M. Goswami of Gauhati University.
There are 27 species of aquatic vegetation, including eyraleferox, in the wetland.
On the measures to be adopted to increase the oxygen level, Goswami said two drugs — O2-max and Oxymar — help to increase oxygen levels when released into the water.
A study on Herpetofaunal Assemblage of Deepor Beel, Ramsar site of Assam, by four researchers last year had proved that unless the authorities take care of the wetland, the beel would continue to diminish.
The flow of industrial effluents and rampant and unregulated fishing in the area has posed a threat to the sustainability of the wetland.
Industries on the northern side of the beel and brick kilns on the banks also pose a threat, the study had said.
It had recommended the treatment of the effluents and a restriction on setting up fishing nets, particularly gill nets, where a large number of snakes get entangled and die.
It had also sought herpetological conservation education among the people of the area and adjacent Chakradeo hill and inclusion of a part of Rani reserve forest within the jurisdiction of Deepor Beel wildlife sanctuary.