Habitats of tiniest fish vanishing fast

Peat swamps that they inhabit are being cleared for agriculture
Grace Chua, Straits Times 6 Jun 09;

THERE may be as many as 12 species of the world's smallest fish, but scientists are racing against time to find and classify them all.

Mature females of the Paedocypris progenetica species, a type of carp related to rasboras and zebra fish, can be as minuscule as 7.9mm and are deemed the smallest fish, as well as the smallest creatures with backbones.
But their peat-swamp habitats in Malaysia, Borneo and Sumatra are in peril from development, said the Singapore researchers who first discovered the fish there.

Dr Tan Heok Hui of the Raffles Museum of Biodiversity Research, is one of the scientists who, three years ago, was credited with the discovery of the species, together with experts from Switzerland, Germany, Indonesia and Britain.

'It's very disheartening - we went up to Malaysia earlier this year to try and re-sample some of the original peat swamps, but they had been cleared for oil palm plantations,' he said.

Peat swamps are formed from waterlogged, slowly decaying vegetation. Their acidic, tannin-rich waters are home to various species of fish, crabs, amphibians and other organisms. Each swampy region generally contains just one species of the fish.

Researchers can net thousands of them in one swamp, but the various species are restricted to this specialised habitat.

So when peat swamps are cleared for agriculture, notably oil palms to meet the rising demand for biofuel, the fish suffer.

Dr Ralf Britz of London's Natural History Museum, who collaborates with Dr Tan to study Paedocypris, said the fish may have evolved to be so tiny because of its nutrient-poor environment.

In 2006, Dr Tan helped to discover the world's tiniest fish, each as small as 7.9mm, about the size of a large mosquito. -- ST FILE PHOTO, PHOTO: MAURICE KOTTELAT

The scientists compared Paedocypris with other fish in the same family, and discovered it was missing bones which appeared in other, larger fish at later stages of development. 'If you mature at that (early) stage, you don't have to grow much or very long to reproduce,' Dr Britz explained. 'That's an advantage when food is in short supply.'

Now, researchers are developing a system to classify the various species of Paedocypris based on patterns and shapes of their coloured spots, and studying its breeding habits and development.

So far, three species have been discovered, but there could be up to 12 because not all peat swamp areas have been studied.

The discovery of the world's smallest fish in 2006 put the Raffles Museum of Biodiversity Research on the world map, attracting attention from biological circles and international media.