Native UK crayfish species under threat from American invader
The crayfish is a freshwater crustacean that looks somewhat like a small lobster. There are two species common in British waterways.
The native British crayfish, or white-clawed crayfish, grows up to around 6 inches in length, and is greenish brown in colour. They are largely nocturnal feeders, spending the daylight hours hidden under rocks and in hollows and crevices in the riverbanks. Their preferred home is clean, clear rivers and streams.
Native crayfish were once common around the UK, but are now in retreat due to competition from non-native imported species. In some areas, notably SW England, western Wales, and Scotland, the native has disappeared almost entirely.
The most common non-native species is the American 'Signal' crayfish. Larger than the native at up to 12", and dark brown to black in colour, it is also more aggressive and has the ability to survive for long periods out of water. This means that it can spread from waterway to waterway by crossing land. Not only can they out-compete natives, they will also feed on them directly, and disastrously carry a fungal disease that is lethal to natives.
The invasion of foreign crayfish stems from the 1970s when farms were set up to supply the restaurant trade. Escapees, and stock from abandoned farms, account for the signals' wild presence today.
Native crayfish are a now a protected species in Britain, while signals continue to be farmed for food purposes.
In culinary terms, signal crayfish can make a delicious meal. The tail meat is tender, tasty, and in texture somewhere between prawns and lobster.
Updated version of Mrs Beeton's recipe with modern measurements etc
Stylish pasta dish with crayfish, white wine and rocket