A COMBINATION of extreme heat and sudden torrential rain triggered a mass fish die-off at Tasik Kelana in mid-April, says Petaling Jaya mayor Datuk Mohamad Zahri Samingon.
The incident, which saw hundreds of dead tilapia floating in the lake in Kelana Jaya, Selangor was first reported by shocked residents on April 15.
Following a comprehensive investigation by Petaling Jaya City Council’s (MBPJ) Occupational Safety, Health and Environment Unit, the phenomenon was identified as “thermal shock”.
Mohamad Zahri explained that intense morning heat significantly depleted oxygen levels in the water and when cold rainwater suddenly mixed with these heated layers, the aquatic life was left unable to regulate their internal systems.
This rapid temperature shift further agitated the lake’s sediment – rich in decaying organic matter – releasing toxic levels of hydrogen sulfide and sulphuric acid.
“Substances such as hydrogen sulfide and sulphuric acid are natural byproducts of organic decay, but in concentrated conditions, they become highly toxic.
“This caused the fish gills to stop functioning, eventually leading to suffocation,” Mohamad Zahri said when met on the sidelines of an event in Petaling Jaya.
He added that the most affected species were black and red tilapia.
While maintenance logs at nearby Kelab Golf Negara Subang confirmed that chemical treatments remained within standard levels, the lake’s ecosystem was simply overwhelmed by climate volatility.
To prevent a recurrence, MBPJ is exploring the installation of submersible aerators and paddle wheels to regulate oxygen levels, while identifying lake desilting as a necessary long-term preventive measure. — By JADE CHAN
