A man was charged yesterday with releasing three venomous Motoro stingrays into the Lower Seletar Reservoir .

Larry Tan Chin Guan, who was unrepresented, told the court he intended to plead guilty to abandoning his pets without reasonable cause or excuse.

The 48-year-old Singaporean, whose occupation was not stated, allegedly committed the offence between 3pm and 4pm on June 2.

The Agri-Food and Veterinary Authority (AVA) told The Straits Times that it was the first time anyone had been prosecuted for abandoning a ray.

Its prosecutor, Mr Yap Teck Chuan, told the court yesterday that Tan will also be charged next week with a related offence involving Singapore's national water agency, PUB.

Responding to queries from The Straits Times, AVA said Motoro rays are allowed to be sold in aquariums as pets.

According to a 2010 report in The Straits Times, the freshwater rays are native to South American rivers and can grow to the size of dinner plates. They had been found previously in Upper Seletar Reservoir and were likely to have been released by hobbyists.

The rays can deliver venomous stings that cause extreme pain and even death. Introducing a non- native species can also upset the delicate ecological balance.

Tan will be back in court next Tuesday.

First-time offenders convicted of abandoning animals can be jailed for up to a year and fined up to $10,000. Repeat offenders can be jailed for up to two years and fined up to $20,000.