African Walking Catfish (Clarias gariepinus) being scavenged by Apple Snails (Pomacea sp.)
Kallang Riverside Park, 2nd February 2015

This photograph of a dead African Walking Catfish was shared by Leroy Alphonso. This invasive species, introduced to Singapore in the 1990s, has effectively replaced the native Common Walking Catfish (Clarias batrachus) in both rural and urban freshwater ecosystems throughout Singapore.

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Dead fish at Bishan Park on Jul 21, 2015 Photos: Calvin Oh

Bishan Park water quality normal despite mass fish deaths: PUB
Despite the death of up to 900 fish in the river running through Bishan-Ang Mo Kio Park, laboratory tests show the raw water quality, including dissolved oxygen levels, is within normal range, PUB says.
21st July 2015;

About 800 to 900 fish were found dead at the Kallang River at Bishan-Ang Mo Kio Park, but the water quality is normal, said Singapore’s water agency PUB.

In a statement, PUB said it was alerted to the problem on Monday (Jul 20) at about 7.40pm. “A site check was carried out immediately and NEA’s contractors were activated to remove the dead fish. Clean-up operations which commenced since last evening at the affected stretch of the river are largely completed,” PUB said on Tuesday.

Laboratory tests showed that the raw water quality, including dissolved oxygen levels, is within normal range, the agency stated.

Most of the fish affected are cichlids (F. Cichlidae). Specimens have been sent to AVA for examination, PUB said. Investigations on the cause are still ongoing.

“As of now, the water quality of the river in Bishan Park is normal, live fishes can be seen in the water and the public can continue with their activities at Kallang River @ Bishan-Ang Mo Kio Park. PUB will continue to monitor the situation,” a PUB spokesperson said

Source: Channel NewsAsia

A dead Tilapia found in the Kallang River at Bishan-Ang Mo Kio Park. Experts suspect that the fish deaths could be linked to the hot weather and reduced rainfall. Photo: Carolyn Khew

Mass fish deaths again at Bishan-Ang Mo Kio Park
PUB says 800 to 900 fish dead in Kallang River; similar incident occurred in February last year
By Carolyn Khew, 22nd July 2015;

Close to a thousand fish went belly up at Bishan-Ang Mo Kio Park on Monday night, in a repeat of a similar incident last year.

National water agency PUB said that the latest incident at Kallang River, which runs through the park, affected about 800 to 900 fish of varying sizes. They were mainly cichlids (F. Cichlidae), a diverse family which includes the popular aquarium fish Luohan (Flowerhorn Cichlid) and the food fish Tilapia (Oreochromis sp.).

Fish specimens have been sent to the Agri-Food and Veterinary Authority of Singapore for examination, and investigations are ongoing, said a spokesman for PUB. It is monitoring the situation.

While the cause of the mass fish deaths is a mystery for now, experts The Straits Times spoke to suspect that, like the incident in February last year which killed about 400 fish, it could be related to the hot weather and reduced rainfall.

Dr Tan Heok Hui, a fish expert from the National University of Singapore’s (NUS) department of biological sciences, explained that this could have led to low oxygen levels in the water. When there is less rain, the water becomes clearer, so sunlight can better penetrate and algae grows faster, explained Dr Tan, who is also a museum officer at the Lee Kong Chian Natural History Museum.

Water samples that the PUB collected for testing showed that the raw water quality, including dissolved oxygen levels, was within the normal range, it said.

The agency received a report of dead fish at around 7.40pm on Monday, and cleanup operations since then have been largely completed, said the PUB yesterday.

“As of now, the water quality of the river in Bishan Park is normal, live fishes can be seen in the water and the public can continue with their activities at Kallang River at Bishan-Ang Mo Kio Park,” said the PUB spokesman.

When The Straits Times visited the park yesterday morning, cleaners were still removing the dead fish. Residents in the area said that the dead fish gave off a pungent smell which wafted over to the main road nearby.

Bishan resident Chen Shanshan, 24, who lives at the block next to the park, said that she could see many dead fish floating in the water even from her eighth-floor flat.

“I saw passers-by gawking and taking pictures and then later, when I was crossing the road, I could smell the dead fish stench,” said the communications associate.

Dr Chou Loke Ming, adjunct research professor at the Tropical Marine Science Institute at NUS, said the mass fish deaths are worrying, and that it could happen again.

“Most would point to the changing climate and that may indeed be true, but we need to investigate to be sure,” he said.

Source: The Straits Times

Photos: Jaslin Goh

Mass fish deaths at Bishan-Ang Mo Kio Park
Investigations still ongoing, public can continue activities at Kallang River, says PUB
By Marissa Yeo, 21st July 2015;

The public may continue their activities at the Kallang River in Bishan-Ang Mo Kio Park, as authorities investigate what killed some 900 fish there despite normal levels of dissolved oxygen, national water agency PUB said today (July 21).

The dead fish were discovered from last evening and specimens have been sent to the Agri-food and Veterinary Authority for examination, said PUB. “Investigations on the case are still ongoing.”

The PUB checked the site after it was alerted at 7.40pm yesterday.

Contractors of the National Environment Agency were activated to remove the dead fish – numbering about 800 to 900 and which were mainly cichlids – and the PUB said clean-up operations were largely completed as of last evening.

Laboratory tests of water samples collected by PUB along the river showed dissolved oxygen levels within the normal range, said the spokesperson. As of this evening, the water quality of the river in the park was normal and live fishes could be seen, she said.

This is not the first time the park has been hit by fish deaths: Last February, about 400 fish died as Singapore underwent a dry spell. The PUB said at the time that the deaths could be because of lower levels of dissolved oxygen due to hot and dry weather.

Although unaffected, some Bishan residents approached today were surprised to find out about the fish deaths.

Ms Koh Lay Bin, who exercises at the park, said: “I didn’t know that there was clearing of the fishes. (Previously), I have seen several fish that died, probably because the water levels were very low; however I will still see some of them swimming.”

Another resident, Mr Patrick Wong, 60, said: “I don’t really see much fishes along river (when I pass by). It may be due to the shallow waters. However, there are more fishes at the bridges because the water levels are slightly deeper.”

Mass fish deaths have been reported elsewhere in Singapore in recent years. In March, wild fish as well as up to 600 tonnes of farmed fish died in the East Johor Strait off Pasir Ris amid an algal bloom. Last year, a plankton bloom cost fish farmers in both the East and West Johor Straits about 500 tonnes of fish.

Source: TODAY

2,000 fish die in Geylang Bahru drain
22nd March 2014;

About 2,000 dead fish were found floating in a large drain near Block 59A, Geylang Bahru early on Wednesday morning.

Witnesses spotted various types of fish floating at around 7am, reported Shin Min Daily News.

Mr Lee, 40, who has been fishing in the area for three years, said the fish could have swum into the drain from a nearby river because of oxygen shortage in the water.

A school bus driver who gave his name only as Mr Tan, 53, said waters in the big drains in the nearby Kallang Bahru area had turned green recently. Others residents feared that if the water is polluted, it may affect the area’s biodiversity

Source: The New Paper (Mirror)

No more fish deaths in river at Bishan park

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

No more fish deaths in river at Bishan park

Hot, dry spell likely behind mass fish deaths in Bishan

By David Ee, 6th February 2014;

The deaths of hundreds of fish, found washed up along a river in Bishan-Ang Mo Kio Park, were likely due to the recent spell of hot and dry weather, experts said yesterday.

Residents spotted around 400 dead Tilapia (Oreochromis sp.) and Mayan Cichlids (Cichlasoma urophthalmus) in clumps along the banks or against rocks along the 3km-long river on Tuesday.

Many were decomposing under the sun, causing a stench that lasted until yesterday afternoon.

However, only two fish species were affected. When The Straits Times visited the river yesterday morning, it was otherwise teeming with life. Numerous terrapins and other fish were seen.

The two affected species are commonly found in canals and reservoirs here, anglers said. Many of them are let loose by aquarium owners.

National water agency PUB said in a statement that it was notified about the dead fish on Tuesday morning and immediately sent contractors to clear them.

The two-day clean-up effort ended yesterday. It also collected water samples for testing and discovered reduced levels of dissolved oxygen in the water.

This was due to the recent hot, dry weather and may have caused the deaths of the fish, said a PUB spokesman.

Its tests also showed that the river’s water quality is unaffected and there is “no contamination”.

Dr Tan Heok Hui, a fish expert at the National University of Singapore (NUS), explained that dry weather could have lowered the river’s water levels and increased algal growth.

This could have led to low oxygen levels as algae competed with fish for it.

The dead fish “could have a low tolerance to oxygen deprivation” compared to other species, he said. “Terrapins breathe air like we do and thus are not affected,” he added.

Mass fish deaths like this are rare, said NUS marine biologist Chou Loke Ming.

Last July, thousands of fish in Lim Chu Kang farms were killed by low oxygen levels, while a plankton bloom killed 400,000 fish off Pasir Ris in 2009.

Long-time Bishan resident A.Tan, in his 50s, said he believed children – some of whom regularly play at the water’s edge – should avoid the park’s river “until it is cleaned up”.

But the PUB assured the public that water activities at the river can continue and that it is monitoring the situation closely.

The picturesque river in Bishan-Ang Mo Kio Park is part of the Kallang River, which runs from Lower Peirce Reservoir down south to Kallang Basin.

It opened in March 2012 after having been converted from a concrete canal under a PUB programme to turn drains, canals and reservoirs into streams and lakes.

Source: The Straits Times

Hot, dry spell likely behind mass fish deaths in Bishan