Hot weather may have caused fish deaths in Bishan-Ang Mo Kio park

SINGAPORE — Hundreds of dead fish were found floating in the scenic river at the Bishan-Ang Mo Kio Park yesterday, with national water agency PUB attributing the mass deaths to the hot and dry weather.

Several residents in Bishan said they were surprised to see clusters of dead fish floating in the usually clean river, with some wondering whether the water had been contaminated. Others had spotted the dead fish on Tuesday afternoon.

“It’s the first time we are seeing anything like this in our river,” said Madam Karen Seah, 56.

Following reports of the sighting on Tuesday morning, the PUB said it immediately deployed contractors to clean up the section of the river between Marymount Road and Bishan Road.

After collecting water samples from the river, “laboratory results showed that the water quality is not affected and there is no contamination”, a PUB spokesperson said.

“However, due to the hot and dry weather, there are lower levels of dissolved oxygen in the water (and) that could have led to the death of the fish. The two species of fish affected are Tilapia and Mayan Cichlid. About 400 fish were affected,” the spokesperson added.

TODAY reported yesterday that the dry spell in Singapore over the past few weeks had prompted the PUB to ramp up the supply of NEWater and desalinated water to maintain water levels in the reservoirs.

When TODAY visited the Bishan-Ang Mo Kio Park yesterday afternoon, workers were seen cleaning up the area, picking up the dead fish near the lower end of the river, opposite Block 221 on Bishan Street 23.

While the change in oxygen levels in the water had a fatal effect on the two fish species, it did not appear to affect other marine life, with catfish and turtles spotted yesterday swimming in the river, which is part of the Kallang River.

Dr Tan Heok Hui, from the National University of Singapore’s Department of Biological Sciences, said this was because “oxygen demand varies for different species”.

For instance, catfish and terrapins breathe air the same way as humans do. Thus, both were not affected by the oxygen content in the water, he said.

The PUB said it released more water from Lower Peirce Reservoir into Kallang River yesterday to improve the circulation and the low dissolved oxygen levels arising from the dry weather.

With clean-up work at the river completed, the PUB spokesperson said: “It is safe for the public to continue with water activities at Kallang River @ Bishan-Ang Mo Kio Park. PUB will continue to monitor the situation closely.”