Tonnes of fish from four farms at the Lim Chu Kang area have died due to the lack of oxygen in the water, said the Agri-Food & Veterinary Authority (AVA).
Some of the close to 90,000kg of dead fish, mainly mullet and milkfish, have also been sighted at Sungei Buloh Wetland Reserve (SBWR).
According to a statement by the AVA, the lack of oxygen is due to the recent hot and dry weather conditions with little rainfall.
Rainfall is important to produce a “churning effect”, which helps to dissolve “atmospheric oxygen” in the water, it said.
Other factors such as “slightly warmer temperatures” have also contributed to the mass death.
Spotted by bloggers
The mass death was initially brought to light on 29 June after a blogger posted photos of the dead fish found on Lim Chu Kang beach as well as at SWBR. The nature lover, who was on a walk with a friend, snapped photos of fish stuck on rocky bunds and trees at SBWR's mangrove boardwalk area.
According to his entry, some of the fish found at SBWR were already producing a “pungent smell of decomposing fish”. He added that he the “SWBR staff had cleared what they could reach but there were just too many”.
On Monday, Ria Tan from nature site “Wild Shores of Singapore” followed up with more photos of the dead fish at Lim Chu Kang.
“The dead fish looked like those raised by fish farms,” she wrote.
The AVA has advised affected farmers to dispose the dead fish and has increased “the frequency of waste disposal” by activating waste disposal companies. It is also working closely with the farms to help with the situation and provide assistance.
One way for farmers to “mitigate” the low levels of oxygen in the water, is by setting up “standby aeration systems”, according to the AVA and it is rendering the necessary assistance.