A pet shop owner was baffled by a strange 'alien fish' with a bizarre facial deformity.

Watcharaphan Chotipradit had bought the black Mekong giant catfish from another store, but was surprised by the unusual shape of its head, with two large discs that appeared to be eyes bulging from the sides.

He named the four-month-old fish Baesae, and displayed it at his store called Fish Village in Ratchaburi province, Thailand.

Baesae's unique appearance immediately caught the eye of store visitors, who likened it to a pug's face.

Watcharaphan said: 'Baesae looks like this because of a genetic abnormality since birth. It's very rare, and will usually result in the animal's death, but Baesae is healthy and continues to grow like a normal Mekong giant catfish.'

He said he had already sold Baesae to an interested customer, but did not disclose the selling price.

The Mekong giant catfish is listed as 'critically endangered' in the International Union for Conservation of Nature Red List.

Its population is decreasing, with overfishing, and habitat loss and degradation cited as the main causes.