A worldwide appeal has been launched to find a mate for the last remaining males of a tropical fish on the brink of extinction.

The Mangarahara cichlid, from Madagascar, is believed to have vanished from the wild as a result of the building of dams, which has dried up its habitat on the Mangarahara river.

Two of the last-known individuals from the species are in London zoo's aquarium, but both are male, the Zoological Society of London (ZSL) said.

Another male is known to be in Berlin zoo but a search for Mangarahara cichlids in zoos and aquariums around the world has failed to find any females.

ZSL is launching an appeal to private aquarium owners and fish collectors to get in touch if they have or are aware of any females in existence, so a crucial conservation programme can be launched to save the species.

London zoo's aquarium curator, Brian Zimmerman, said: "The Mangarahara cichlid is shockingly and devastatingly facing extinction; its wild habitat no longer exists and, as far as we can tell, only three males remain of this species.

"It might be too late for their wild counterparts, but if we can find a female, it's not too late for the species.

"We are urgently appealing to anyone who owns or knows someone who may own these critically endangered fish, which are silver in colour with an orange-tipped tail, so that we can start a breeding programme here at the zoo to bring them back from the brink of extinction."