Malacostracans · Decapoda · Astacidae

Signal Crayfish

Pacifastacus leniusculus

Least Concern

The species is abundant and widely distributed; it faces no significant short-term risk. See full glossary

The signal crayfish, or Pacific crayfish, is a freshwater decapod native to the west coast of North America. It was introduced into Sweden in 1960 to replace the populations of the native crayfish Astacus astacus, which had been hit by crayfish plague. It has since been introduced throughout Europe.

Diet

Omnivore

Combines animal and plant food depending on availability.

Social structure

Solitary

Lives and hunts alone, joining others only to breed.

Sighting difficulty

Easy

FreshwaterOmnivore Solitary Freshwater Crustacean

31countries2same family

Fun facts

GeneralIt carries the crayfish plague fungus, which has decimated the native crayfish.
It was introduced into Spain in 1974-75, first in fish farms at the headwaters of the Duero and the Tagus. In the 1980s it was stocked in the north, including Navarre, Castile and León and the Basque Country.
Like the red swamp crayfish, it is a chronic carrier of crayfish plague, lethal to the native species.
It is called the signal crayfish for the pale patch at the claw joint, which recalls a railway signal flag.
Its pattern of spread differed from the red swamp crayfish's: it expanded through translocations from hatcheries, not from a single focus.