Ten thousand chilwa — a variety of freshwater fish — will be released into the Powai lake on Saturday, World Earth Day, 15 years after the species was declared extinct here.

Chilwa is usually about six inches in length, the biggest specimens growing up to a feet in length. It has a long more or less compressed body with a small head and upturned mouth. A bright silvery fish, covered with minute silver scales which come off very easily when handled.

It’s a clear victory for the Maharashtra State Angling Association (MSAA), which has spearheaded efforts to clean up the polluted and neglected water body.

“Our task is to protect the predator at the top of the food chain here, the crocodile, and the prey at the bottom of the chain, the chilwa fish. As long as we make sure those two species are safe, all other life in the lake will be in good health too,” says Ali Husseni, a senior MSAA member.

This would not have been possible if the MSAA had not worked tirelessly to clean up the lake, raising its oxygen levels and ability to support aquatic life.

The Powai lake’s environmental crisis began 16 years ago.

“During the real estate boom, several builders pumped out the lake’s water for construction to the point that the lake was fragmented into four sections,” says environment consultant Pramod Salaskar.

As the buildings came up and residents moved in, they began dumping plastic and other waste in the lake. Some freed aquarium fish into the lake, upsetting the ecological balance.

Then, the MSAA stepped in and called upon the Centre to help protect the lake.

The Union Ministry of Environment & Forests put the Powai lake on a list of just 20 others across the country to be protected and rejuvenated under the National Lake Conservation Mission.

Under this mission, the Brihanmumbai Municipal Corporation (BMC) would implement a pre-determined conservation plan.

“We installed six aeration devices in the lake, which constantly improve oxygen levels. Every month, we also introduce certain bacteria into the lake to break down its pollutants,” says BMC executive engineer Manohar Pawar.

The MSAA pitches in by periodically clearing the plastic waste in and around the lake.

The results have been encouraging.

Water quality tests conducted by eco consultant Salaskar in January show a definite improvement in dissolved oxygen levels, (up to about 7 mg/litre against 2.8 in 1994, and a minimum required level of 4 mg/litre). Water alkalinity, which should be between 7 and 8.5 mg/litre, is now a healthy 7.6.

“If this healthy trend continues,” says a hopeful MSAA general secretary Baqar Shaikh, “Powai lake could soon be restored to its former glory.”

News source http://www.hindustantimes.com/special-news-report/rssfeed/An-Earth-Day-gift-for-Powai-lake/Article1-553295.aspx