Large scale fish deaths in Kandy Lake attributed to pollution

By Ifham Nizam

National Aquatic

Resources Research and Development Agency (NARA) preliminary research clearly indicates that large scale fish deaths in the Kandy Lake is due to pollution and over population.

NARA Researcher, Dr. Deepthi Amarasinghe who headed the probe team told The Island that there was major pollution in the Kandy Lake. The situation had worsened with rains when nutrients and organic matter got washed into it from the surrounding hills.

He also said that their study also indicated secondary infection. 

Fish started to die suddenly in the Kandy Lake last week and this has been happened earlier in April 2000, too. The Lake has a perimeter of 2.1 miles and maximum depth of 60 feet.

Dying of fish in large numbers was a concern of the people there and visitors to the sacred city as the rotting fish also causes a nasty odour and an ugly patch on an otherwise beautiful city.

Irangani Tumpale, Senior Staff Technical Officer, National Institute of Fundamental Studies says first reason is over density of the fish population.

 Since the banning of fishing has caused an explosion of fish population and most of the fish belonged to the ‘Thilapia’ variety which breeds fast.

 "Even if 50 per cent of the fish were removed from the lake it will not help control their breeding. As most of the dead fish are old ones, it is suspected that natural selection is taking place to control the bio diversity in the lake. Animals and birds around the lake are not sufficient to control the fish count," she said.

Second reason which researchers believe is the depletion of oxygen in the water.

Several institutes have already measured dissolved oxygen in the lake, but none of them has found significant depletion of dissolved oxygen level.

But, it is understood that measuring dissolved oxygen in the lake at both night and day time is important to determine the dissolved oxygen level in the water body.

Checking the phytoplankton density of the lake by National Institute of Fundamental studies, Kandy found that there are no toxins forming algae at present. However, diatomic algae species and few cyanobacteria algae species were found in the lake water.

Third reason attributed is dumping of garbage into the lake. Kandy Lake is surrounded by schools, hotels, restaurants, hospitals and other crowded areas. There are four major inflows that enter the Kandy Lake. They are Rathubokkuwa inflow, VGS inflow, Mahamaya inflow and Saranankara inflow.

The management of water quality of inflows is very much important to the conservation of biodiversity of this type of small lake, experts say.

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