SINGAPORE - Designated fishing grounds at Lower Peirce Reservoir and Upper Seletar Reservoir will be closed until further notice, water agency PUB said.

Motoro stingrays, which are non-native to Singapore, were spotted at Lower Peirce Reservoir last week, with a Lianhe Wanbao reader claiming that 60 motoro stingrays were seen at the reservoir.

The PUB said that the number of stingrays in these water bodies have yet to be determined.

It is currently conducting investigations and removing stingrays from the two reservoirs, the agency added.

Mr Huang Hongguo, 70, told Wanbao that the number of stingrays in the reservoir have increased greatly in the last four to five years.

The Straits Times understands that the stingrays may have been released into the reservoir by members of the public.

"The release of animals into our waters may impact the water quality of our water sources, and may pose a risk to users of our water bodies," PUB said.

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Members of the public are urged not to release animals into reservoirs and waterways.

Seventy-five motoro stingrays have been removed from these water bodies since 2015, PUB said.

The water agency has been working with the National Parks Board and the Agri-Food and Veterinary Authority of Singapore (AVA) on Operation No Release, which seeks to raise public awareness on the harmful impact of releasing animals into reservoirs and waterways.

It is an offence to release animals, including fish, into reservoirs and waterways in Singapore, PUB said. Those caught doing so may be fined up to $3,000.

Last year, a 48-year-old man was fined $2,600 for releasing three motoro stingrays into Lower Seletar Reservoir.

If members of the public spot people releasing animals into water bodies, they can call the PUB hotline on 1800-2255-782 (1800-CALL-PUB), or the AVA via its 24-hour hotline 1800-476-1600.