Chandigarh: Around 30 dead fish were found floating in the manmade Sukhna Lake here, leading to apprehensions that the aquatic life in the lake may be under threat, officials said.

The dead fish which have been found during the last six days were immediately removed from the lake to avoid further contamination and their samples were sent to the Panjab University's Department of Zoology for tests.

"I have scrutinized the dead fish and also visited the lake. Our observations say that the fish have died due to over population and lack of oxygen. They have not died of any external injury as they seemed quite healthy," M.S. Johal of the zoology department told sources.

"Here Darwin's theory of survival of the fittest holds true. Due to a bad immune system, these fish could not tolerate the deficiency of oxygen in the lake water," Johal said.

"This usually happens during the monsoon season when there are clouds all over and we do not have enough sunlight. This led to the decline of oxygen level and the rise of carbon dioxide in the water. The fish could not get enough oxygen and they died," Johal added.

He added: "Another reason that we found is the excess of silt in the lake water as our investigations revealed the presence of sand granules in the gills of fish. That resulted in the cutting down their access to the outside oxygen."

"We have to keep a check over the population of fish in the lake water so that there would be no scarcity of nutrients and oxygen for the fish. All the fish found here are edible and of good quality," Johal said.

"Therefore, our administration has to make arrangements of catching them and selling them at regular intervals to prevent over population and such kind of mortality in the future. It will also help to maintain the ecological balance," Johal added.

Water samples from the lake were also collected by the concerned authorities to check for the presence of heavy metals or any other poisonous substances in the lake.

"Normally we conduct regular tests of the lake water to ensure that is there is no threat of any polluting agent in the water. Earlier also we had found some dead fish during the rainy season but there is no danger to other aquatic and wildlife in the catchment areas," a senior official of Chandigarh's forest and wildlife department said.

Sukhna Lake is an artificial, rain fed lake situated in the foothills of Shivalik hills in Chandigarh. It was excavated in 1958 and currently sprawles over an area of 340 acres. It is fed by tributaries that bring rainwater from the higher regions.

Sukhna Lake also serves as a sanctuary for various species of birds. Around 30 species are residents and the rest are migratory. IANS