European crayfish, Noble crayfish, Broad-fingered crayfish
Astacus astacus, the European crayfish, noble crayfish, or broad-fingered crayfish, is the most common species of crayfish in Europe, and a traditional food source. Like other true crayfish, A. astacus is restricted to fresh water, living only in unpolluted streams, rivers, and lakes. It is found from France throughout Central Europe, to the Balkan Peninsula, and north as far as Scandinavia and Finland, and Eastern Europe. Males may grow up to 16 cm long, and females up to 12 cm.
European crayfish feed on worms, aquatic insects, molluscs, and plants.
They are nocturnal, spending the day resting in a burrow. They prefer habitats with high levels of shelter availability. The waters they are found in tend to be soft-bottomed with some sand, and they do not tend to be found in muddy water.
A. astacus become sexually mature after three to four years and a series of moults, and breed in October and November. Fertilised eggs are carried by the female, attached to her pleopods, until the following May, when they hatch and disperse.
The main predators of A. astacus, both as juveniles and adults, are European mink, eels, perch, pike, Eurasian otters, and muskrats. There is also some risk of predation via cannibalism.
A. astacus is sensitive to dips in oxygen levels in the water it inhabits, which makes it particularly vulnerable to eutrophication. However, they are capable of tolerating lower calcium levels than most other species of crayfish.
A. astacus is regarded as a keystone species in the environments it inhabits. Crayfish are an important part of the freshwater food web as they provide a source of food to many aquatic species and boost primary productivity by foraging on freshwater plants. The loss of crayfish in a freshwater environment is known to cause macrophyte growth, which can be a cause for eutrophication and an overall degradation in water quality.
