Looking for crayfish in Britain? Look hard. Almost 95 percent of British crayfish have been wiped out in the last 20 years. Now some of the few remaining crustaceans are going into hiding in a desperate, last-gasp chance to save their species from extinction.

Like so many problems around the world, this one can be placed squarely on the heads of Americans—although in this case, we're talking about American signal crayfish (Pacifastacus leniusculus). First introduced to Britain two decades ago as food for trout farms, American crayfish have made their way into the wild. They not only outcompete the local white-clawed crayfish (Austropotamobius pallipes) for food, but they also carry crayfish plague (Aphanomyces astaci), a water mold that is deadly to the British crayfish.

Signal crayfish themselves are immune to crayfish plague, but over the last two decades, they have carried and distributed it to rivers and ponds throughout Britain. White-clawed crayfish are the only crayfish species native to England and Ireland, and they have no immunity to the mold.

Death by crayfish plague is particularly nasty and occurs within weeks of infection. Water wildlife conservationist Chris Rostron told the BBC in 2006 that a white-clawed crayfish killed by the plague "might look fairly normal from the outside, but if you break open the body there'll be nothing inside except fungus. It literally eats them alive, like something out of Alien."

Now, with just a few uninfected populations of white-clawed crayfish left, a two-year, £210,000 ($345,000) breeding program hopes to preserve the species from extinction. The South West White Clawed Crayfish Conservation Group has recently started trapping British crayfish and moving them to two secret locations, "safe haven" sanctuaries where they will have "little chance of being affected by the American species," according to a report in the Guardian. Jen Nightingale, conservation officer for the Bristol Conservation and Science Foundation, which is leading the project, told the paper, "We want to keep these locations secret to prevent people visiting the areas and risk spreading crayfish plague—which can be carried on damp equipment and boots as well as in water."

The team hopes that this project will allow the white-clawed crayfish to re-establish itself in a fungus-free zone, and in the process save the species from total annihilation.

Image: White-clawed crayfish (Austropotamobius pallipes) via Wikipedia