Five years after the hit film that endeared the clownfish to audiences the world over, Nemo is becoming increasingly difficult to find.

The lovable tropical species, immortalised in the smash Pixar movie Finding Nemo, is facing extinction in many parts of the world because of soaring demand from the pet trade, according to marine biologists.

Parents whose children who fell in love with Nemo at the cinema are seeking out the clownfish in ever greater numbers, leading to over-harvesting of wild specimens because captive breeding programmes cannot cope with demand.

Dr Billy Sinclair, of the University of Cumbria, who has been studying clownfish populations for five years, says the species should now be listed as endangered.

Studies of clownfish on Australia’s Great Barrier Reef have revealed a dramatic population decline since the release of the movie in 2003. Shoals that used to number dozens of clownfish have dwindled to just a few specimens, leaving them with difficulty breeding, Dr Sinclair says.

“In one coral reef we looked at in Keppel Bay, clownfish populations have dropped from 25 to just six in two years,” he says. The number of clownfish caught accidentally by commercial fishing operations had also seen a large drop since the movie’s release.

Over-harvesting for the pet trade at a time when many reefs are starting to die back from bleaching - caused by rising sea temperatures - is thought to be the main culprit.

Dr Sinclair said the film – the best-selling DVD of all time at over 40 million copies – had done much to educate children about marine life. But as the tiny, brightly-coloured creature had since become a “must-have” pet, captive breeding programmes could now only meet about 50 per cent of demand. The rest are captured from the wild.

In Australia, small salt-water aquariums with an anemone and two tiny clownfish are sold for as little as AUS$50 (£24) and marketed as the essential marine gift for children. The timid fish, ranging from orange to black in colour with white bands and averaging three inches in size, have a symbiotic relationship with sea anemones, from which they will rarely venture far.

“I am not saying it is solely down to over-harvesting as climate change is clearly having an impact on the coral reefs and anemones on which the clownfish live,” Dr Sinclair says.

“But existing harvesting programmes will have to be reviewed in the light of what is happening to the reefs or we could see local extinctions in the near future.”

Finding Nemo, an Oscar-winning Disney/Pixar animation which took over $864 million at the box office, tells the story of a boy clownfish who is captured on his way to school by a scuba diver. His father Marlin then embarks on a mission to rescue him from a tank in a Sydney dentist’s office.

With a central message against keeping marine life in captivity, the film featured a host of Hollywood stars such as Ellen DeGeneres, Willem Defoe and Geoffrey Rush.

Following its release, it became a favourite screening at snorkelling and diving hotspots around the world. But within months, the scuba diving industry was reporting a steep decline in sightings of the diminutive creature, while some pet suppliers saw an eight-fold increase in sales.

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