By Alister Doyle, Environment Correspondent

OSLO, Feb 19 (Reuters) - Freshwater fish can be introduced more safely than expected to new regions for farming with fewer than 10 percent damaging wildlife in their new homes, a scientist said on Tuesday.

Many countries wrongly view alien fish species -- such as trout, catfish, perch or salmon -- as posing a big risk when put in new rivers and lakes, said Rodolphe Gozlan, a French scientist who works at Bournemouth University in Britain.

"We shouldn't exaggerate the risks of non-native species," Gozlan, who also advises the European Commission on the safety of fish farming, told Reuters.

"The risk of ecological impact after the introduction of a freshwater fish species is less than 10 percent for the great majority of fish species introduced," he wrote in the March edition of the journal Fish and Fisheries.

Some types, such as the perch or catfish, were more likely to cause disruptions. But many nations had accepted the view that all alien fish was "guilty until proven innocent", he said.

A study of 103 introduced fish species in an aquaculture database by the U.N.'s Food and Agriculture Organization showed that 54 were reported with no adverse impact on their new habitats, he said.

"Fish farming will expand around the world in coming years," Gozlan said. "Overfishing at sea is not sustainable and we will have to rely more on farmed fish."

That meant it made more sense for governments to assess the risks of new species rather than seek to ban them.

Gozlan said widespread worries about alien species of animals and plants marked a shift from a view common in the 19th century that new species were beneficial.

France set up group to encourage introduction of new species in 1854, for instance, and Britain followed in 1860 with the "Society for Acclimatisation of Animals, Birds, Fishes, Insects and Vegetables".

With time, many species had blended in. Rainbow trout introduced from North America, catfish from Africa and carp from Asia were widely viewed as beneficial in Europe. "After a while people widely accept them as native species," he said.

Even the widely accepted villains among alien species, such as zebra mussels in the Great Lakes of North America or the Nile perch in Lake Victoria in Africa, might be less damaging than expected, Gozlan said.

The mussels, brought accidentally from the Black Sea, are blamed for clogging inlet pipes of power stations for instance, but are a new food source for some species of fish and birds.

The Nile perch, introduced to Lake Victoria about 60 years ago as a new food source for local people, is widely blamed for eating other fish.

But the perch created a big new fishery that attracted ever more fishermen, often using smaller-mesh nets. The fishermen also chopped down trees around the lake to smoke the perch, helping wash more sediment into the waters.

-- For Reuters latest environment blogs click on: http://blogs.reuters.com/environment/ (Editing by Mary Gabriel)

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