By Lim Yan Liang, 7th February 2014;
No more dead fish have been found at the Kallang River in Bishan-Ang Mo Kio Park, national water agency PUB said on Thursday.
Site inspections by its staff have also shown “no abnormalities” in live fish in the river.
Around 400 dead Tilapia (Oreochromis sp.) and Mayan Cichlids (Cichlasoma urophthalmus) were spotted along the 3km river’s banks and against rocks on Tuesday. The agency said the deaths could have been caused by reduced levels of dissolved oxygen in the water arising from the recent dry spell.
It said it has taken measures to return the dissolved oxygen levels to normal, following a two-day clean-up of the area that ended on Wednesday.
“We have released more water from Lower Peirce Reservoir into Kallang River since Wednesday afternoon to improve the water circulation,” said a spokesman on Thursday. “This has increased the dissolved oxygen levels. Water samples were also collected today and the dissolved oxygen levels in the river are back to normal.”
Noting the current long dry spell, conservation experts said that man-made ecosystems need more frequent checks during periods of seasonal change.
“The Bishan river system is a very shallow river system so when you have a dry spell, the water level lowers and this kind of thing can happen,” said wildlife consultant Subaraj Rajathurai. “Artificial ecosystems need to be managed with more regular and stringent checks so any adjustments needed can be carried out sooner, rather than waiting for mass deaths to trigger a response.”
The PUB said this was the first case of mass fish deaths at the Kallang River in Bishan-Ang Mo Kio Park, and that the water quality is not affected.
Source: The Straits Times