North American crayfish introduced to Britain now threaten native species

In the 1970s, British aquaculture businesses imported North American signal crayfish to stock farms, hoping to build a profitable new freshwater fishery. But the plan backfired: the hardy invaders escaped into rivers, multiplied rapidly and spread across England, Wales and Scotland. Today they dominate many waterways and carry crayfish plague, a disease that is usually fatal to the UK’s only native crayfish, the white-clawed species. The UK Government documents describe signal crayfish as a textbook case of how non-native species can damage biodiversity, out-compete natives and alter river ecosystems. This story is based on UK government policy reports and recent Environment Agency reporting on native crayfish conservation. Read on to know more:How signal crayfish arrived, and why they spread so fastSignal crayfish (Pacifastacus leniusculus) were brought into the UK from North America in the 1970s for farming, intended as a commercial species for restaurants and local markets. They are larger, faster-growing and more aggressive than the native white-clawed crayfish (Austropotamobius pallipes), giving them an immediate advantage in competition for food and shelter.Once they escaped ...