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Signal Crayfish

Scientific Name:

Pacifastacus leniusculus




Both flowing and stationary water bodies


Native to the Pacific Northwest; widespread across at least 20 countries


Least Concern (IUCN Red List)

This species is


to the Truckee Meadows.


Crayfish are mostly nocturnal, freshwater crustaceans that resemble small lobsters. Mature adults can grow up to 7 inches long. Most commonly gray or light brown, crayfish (or crawdads) molt their shells several times throughout their lives and can range from grey to blue to brown to copper to tan depending on the time of year and their lifecycle. Crayfish are omnivores and will eat almost anything that comes in between their claws, living or dead. Crayfish have two large pincers near their heads that they use for catching prey, self defense, and mating displays. Crayfish have four pairs of legs, each with their own small claws for grasping prey and their environment. Females will carry their clutch of several hundred eggs underneath their abdomen (the tail). When threatened, crayfish will display their claws as a warning and swim backwards using their tail to quickly move through the water away from danger.

Fast Facts:

  • Also called crawfish or crawdads, crayfish are a prized freshwater food worldwide.

  • Crayfish mothers will protect their young after hatching for several moltings.

  • In most places where crayfish are invasive, it is illegal to put them back into the water once caught.

  • Signal crayfish are the only species of crayfish found in the Truckee River watershed. They are usually a gray/blue color, and mature adults can be identified by red coloration on the undersides of their two main claws.

  • Crayfish prefer cooler water temperatures. They live in both moving water and on the bottoms of lake beds. In streams and rivers, crayfish prefer to stay in the faster parts of the water under rocks or downed trees and root systems. Moving water provides them with ample food and better protection from predators. Signal crayfish will also tunnel into the sediment, affecting water clarity where they are found.

  • Native to the Pacific Northwest, the signal crawfish ranges from British Columbia all the way down to Nevada, California, and Utah. They can also be found across the world in at least twenty other countries!



Kevin Livingstone (research & content)

Alex Shahbazi (edits & page design)

Last Updated:

March 27, 2024 at 1:48:22 AM

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