Scientists and conservationists from around Europe will gather this week at a conference to discuss how to save the U.K.'s white-clawed crayfish (Austropotamobius pallipes) from the fungal plague that is rapidly wiping them out.

As I wrote last year, around 95 percent of British crayfish have been killed in the past two decades, victims of imported American signal crayfish (Pacifastacus leniusculus), which were introduced into the U.K. as food for trout farms and escaped into the wild. The larger North American species not only out-competes the native crayfish for food, it also carries a deadly water mold called crayfish plague (Aphanomyces astaci), from which the British species has no immunity.

Crayfish plague is deadly within weeks of infection. It eats an infected crayfish from the inside, leaving nothing but a hard, empty, lifeless shell.

White-clawed crayfish are the only crayfish species native to England and Ireland, where they are an important part of river ecosystems.

In October the International Union for Conservation of Nature and Natural Resources (IUCN) declared the white-clawed crayfish to officially be "endangered." This month, Bristol Zoo Gardens will host the conference, "Species Survival: Securing White-Clawed Crayfish in a Changing Environment," to "bring together projects and experts from around the U.K. and Europe to create better links and provide a forum of discussion regarding U.K.-wide strategy for the conservation of white-clawed crayfish," says Maddy Rees, U.K. conservation and communication officer for the Bristol Conservation and Science Foundation (BCSF), which is organizing the event.

White-clawed crayfish might seem like an insignificant species to worry about, but Rees says they are both valuable and highly preferable to the invading Americans. "The native white-clawed crayfish is considered a keystone species and indicative of health in the habitats that it occurs," Rees says. "This is because they are an important link in the natural food web of freshwater habitats, particularly rivers and streams. They provide an important food source for larger animals such as otters and herons, and sustain a subtle balance within the invertebrate community, as they are active predators on smaller animals."

While the American crayfish grow to twice the size of the British variety (and presumably taste just as good to a non-discriminating otter), "an influx of these crayfish can cause an imbalance in the biodiversity of the habitat," Rees says. "North American signal crayfish also burrow into banks much more extensively than native white-clawed crayfish and have been known to cause considerable damage along rivers and in fisheries."

Rees is also part of the South West Crayfish Project, which for a couple of years has been moving crayfish to secret locations that are, to date, safe from the plague. Now in its third year, the project is the "largest strategic translocation, or re-homing program in the U.K.," Rees says. The effort has so far moved crayfish to eight new "ark" sites and plans on creating additional refuges next year. "This may seem a small number," she says," but we have lost up to 70 percent of our white-clawed crayfish populations in the southwest [of England] over recent years, and there are only about 20 abundant populations left, so eight new sites is actually increasing the existing populations by approximately 40 percent."

The safe-haven sites are closely monitored and protected by strict protocols that prevent volunteers from carrying plague into the new habitats. "The breeding program has seen some success, and we are maintaining a stable population of adults and juveniles," Rees notes. "There is little published work on white-clawed crayfish breeding methods, and we are researching the best methods of husbandry—which is something that Bristol Zoo Gardens prides itself on—and also on the best techniques to ensure good hatchling success." This year's crayfish breeding season has just begun, and eggs fertilized this month will be carried by females until they hatch in June.

Unfortunately, the project is nearing the end of its three-year funding. "We hope to secure funding to continue," Rees says, "however, monitoring of our ark sites will continue regardless of whether further funds are secured." The project is a partnership led by BCSF. Other partners include Avon Wildlife Trust, Environment Agency, Buglife, Bristol Water, and Natural England.

Rees is hopeful that the IUCN "endangered" designation will help further work to preserve the white-clawed crayfish. "The IUCN Red List of Threatened Species is internationally recognized and has become an increasingly powerful tool in the guidance of government and scientific institute legislation and practical conservation work," she says. "The new designation of 'endangered' for white-clawed crayfish greatly highlights the need for action to ensure the survival of this U.K. species."

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