A seafood salesman has been found guilty of smuggling more than £53m worth of endangered live eels out of the UK.

Gilbert Khoo, 66, transported the rare elvers from London to Hong Kong hidden underneath other fish between 2015 and 2017.

He was caught after Border Force officers found 200kg of the European “glass eels” (Anguilla anguilla), which are critically endangered, at Heathrow airport in the first seizure of its kind in the UK.

Khoo was found guilty of three counts of failure to notify movement of animals and three counts of evasion of a prohibition or restriction on the export of goods at Southwark crown court on Friday.

The Crown Prosecution Service (CPS) said he smuggled more than five million elvers over a two-year period with an estimated retail value of more than £53m in east Asia.

Gilbert Khoo. Photograph: NCA/PA

A picture released by the National Crime Agency (NCA) shows him holding two gold bars. The NCA senior investigating officer, Ian Truby, said: “The entire operation run by Khoo to trade in these critically endangered animals was illegal from start to finish, and there is no doubt his sole motivation was money.

“The profits to be made from illegally smuggling live eels to Hong Kong and the far east are significant. But the NCA are determined to protect vulnerable wildlife from criminals who wish to benefit financially.”

Khoo, from Chessington in Surrey, kept the live eels, imported from countries within the EU, in a barn in Gloucestershire before repackaging them to be exported to Asia.

The NCA says eels fetch more than 10 times the price they would in the UK on the east Asian black market, where they are considered a delicacy and are in high demand. There are strict controls on the export of European eels because of their status as an endangered animal.

Marion Longford, the unit head of the CPS specialist fraud division, said: “Khoo was trading these animals purely for a financial gain. He had no regard for the controls in place for trading endangered European eels, which are vital to safeguard animals increasingly at risk of being wiped out completely.

“We would like to thank Border Force and the National Crime Agency for their investigative work. We take crime against protected animals incredibly seriously and take every step we can to secure convictions in these cases.”

She said such crimes had a big impact both on the environment and on communities, adding: “Which is why we’re committed to building cases against offenders and ensuring they’re held to account for their actions.”

Khoo will be sentenced on 6 March.