Rampant Louisiana crayfish threaten future of French frogs

Transatlantic relations reached a new low yesterday amid reports that a species of voracious giant crayfish from the United States is nibbling away at the French coastline.

Transatlantic relations reached a new low yesterday amid reports that a species of voracious giant crayfish from the United States is nibbling away at the French coastline.

The humiliation, for France, is compounded by the fact that the crustacean abomination - Procambarus clarkii - hails from Louisiana, the former French colony which France sold for a trifle in 1803.

The invader delights in preying on delicate French frogs and defenceless tadpoles, as well as devouring little fish and aquatic plants. "Wherever they go, there is no plant life left," said environment campaigner Jean-Marc Thirion.

Wetland warden Stéphane Builles said the bright red invader with its giant pincers multiplies at an alarming rate in hidden seabed galleries with discreet aeration chimneys. In these sub-aquatic dug-outs, each female lays up to 700 eggs, twice a year. Scientists say that in the northern Gironde region of the Atlantic coast and in all the marshlands lining the Garonne river, the population of the crayfish - whose 20cm length gives them unrivalled paddling power - has reached up to 3 tonnes per hectare.

M. Builles, who is based at the Bruges wetland reserve near Bordeaux, first came across a breeding colony in 1999. "It was the first time we had been confronted with this invasive species which carries a fungus that decimates our own white-legged crayfish," he said.

Further east, in the Landes region, Patrick Dulau, director of nature conservation, said the species was on the march like an invading army. "I have seen them crossing roads in little groups to get to wetland," he claimed. "From the Gironde estuary, they have already made their way to Charente-Maritime, 100km away. In 2002, they reached the Atlantic island of Oléron."

Yet the French happily imported the sinister seafood in the 1970s when supplies of indigenous crayfish suddenly declined and restaurants wanted to keep filling their plateaux de fruits de mer .

Then, in 1983, when local stocks had recovered, the importation into France of Lousiana crayfish was banned. Too late: Procambarus clarkii was already embedded. "There is nothing we can do. We cannot get rid of it," said M. Builles who added that attempts to use cages to trap and destroy the crustaceans had not significantly reduced the population.

Even migrating birds, with their considerable appetites, cannot be relied upon to eat the crayfish fast enough. What is more, the red menace is affecting the physical characteristics of birds that choose France as a resting place.

Jean-Claude Barbraud, an amateur birdwatcher who feeds data to a national research programme on herons, black kites and storks, said he had observed changes in migrating birds since 1978. "In the space of a few years, the legs of young storks, which used to be black with yellow spots, have turned reddish. Even the skin around the wings is red," he said.