Mass fish deaths in Bengaluru lakes a wake-up call for authorities

The increasing fish mortality cases in India have found a place in the research papers. A study has revealed that the maximum fish mortality cases have been reported from Bengaluru followed by Mysuru. These cases have been making news since long. So, what is the exact reason behind the deaths of hundreds fishes? Well, the reason is only one – the sustained release of untreated sewage and chemicals into the water bodies. The study on Recurring Fish Mortality Episodes in Bengaluru Lakes by Indian Institute of Science (IISc) has found that releasing sewage and chemicals into the water bodies leads to a dip in dissolved oxygen (DO) levels.

It is not enough just to clear the dead fish from the water bodies, it’s high time the authorities wake up and take some concrete steps to save the aquatic life. "Ulsoor Lake falls under category E of Inland Surface Water, which means the water can be used only for irrigation, industrial cooling or controlled waste disposal," said professor TV Ramachandra of the Centre for Ecological Sciences, IISc. 

"The sustained inflow of untreated sewage into the Ulsoor Lake has flooded the aquatic ecosystem with nutrients," he added. 
11 years ago in January, first dead fish case was witnessed in Bengaluru’s Ulsoor lake. Back then, increased oxygen demand and chemicals flushed into the lake was the reason behind the fish mortality. Then, the second incident took place in January 2005 when the Ulsoor swimming pool was cleaned and pollutants were thrown into the lake.

The third incident was reported on March 7, 2016 and the reason was the release of untreated sewage that made the oxygen levels to drop to abysmally low levels. IISc researchers analysed the water samples and fish samples and came to a conclusion that asphyxiation was the reason behind the fish mortality in Ulsoor and Devarabeesanahalli lakes as the DO levels in some locations fell.

Similarly, the Kukkarahalli lake in Mysuru registered the incident of fish mortality in 2001, while another lake named Karanji in 2014. The reason in both the cases was the discharge of effluents in the lakes. Andhra Pradesh is second worst in terms of fish mortality followed by Madhya Pradesh and Kerala.