A large number of fish was found dead in two cities in the State on Saturday — at Karanji lake in Mysore and in Kuntegadde tank in Bellary. Depletion of oxygen owing to sudden increase in organic content is said to be the cause of the fish kill.

Broken pipes

The incident came to light early in the morning in Mysore when zoo authorities sighted dead fish floating in the lake.

B.P. Ravi, Executive Director, Mysore Zoo, said because the underground drainage (UGD) pipes were broken at three points and manholes were choked, there was a sudden inflow of sewage into the lake through the storm-water drain. As a result, the dissolved oxygen level in the water plummeted, resulting in the fish kill.

“However, it was confined to one portion of the lake. The city corporation engineers are at work and sewage flow is being plugged to restore normality,” he said, adding that over 500 fish died on Saturday.

Mysore is home to many major lakes and there are apprehensions about the fate of other water bodies in the city as the sewage lines are yet to be diverted. This includes the Kukkarahalli lake, Lingambudhi lake, Dalvoy, Hebbal and Devanoor lake.

K. Jayaramaiah of Kukkarahalli Lake Protection Society said work on diverting sewage lines from Kukkarahalli lake was on and would be completed in two months. He said the freshwater flow had diluted the organic content in the lake and the dissolved oxygen level was 6 to 7 milligram/litre, which was sufficient to sustain aquatic creatures. Earlier, it was down to 2 to 3 mg/l and this caused fish kill, he added.

Similar incidents were reported from Dalvoy lake, Lingambudhi lake and Yennehole a few years ago, and blooming of algae was found to be the reason, said K. Manu of Mysore Amateur Naturalists.

Poor maintenance

In Bellary, one of the reasons that might have caused the fish kill was improper maintenance of the water body.

Workers were seen removing the dead fish when this correspondent visited the spot. Shivanna, Assistant Director of Fisheries, told The Hindu that the common carp variety lives deep in the water. The sudden drop in the temperature owing to cloudy weather, would have led to reduced level of oxygen in the lake.

Mr. Shivanna said a couple of months ago, following reports of the death of fish in the same tank, he had suggested cleaning the tank and giving medicines to the fish.

To a question, he said he had received a letter a few days ago from the Assistant Commissioner’s office to call for tenders to clean the tank.