The Mekong giant catfish is being put on a list of "critically endangered" creatures because its numbers have plummeted so much in recent years.

The fish grows up to three metres long and can weigh as much as 300 kilograms.

One animal-lover has started paying fisherman to give him the catfish they catch. So far, he's saved 19 of the creatures from the local market.

Catfish used to be common throughout Thailand, Cambodia and Laos.

Now they are so rare that the authorities have ordered that each one caught is tagged, weighed and released.

But they remain popular for their meat and often get caught up in the huge fishing nets which line the local rivers.

Their survival is also threatened by pollution and new dams affecting the flow of the river.