One of several Signal Crayfish (Pacifastacus leniusculus) carcasses along the bottom of the river on Mar. 17, 2015. Photo: Joanna Rutkowski.

The remains of a Signal Crayfish (Pacifastacus leniusculus) on the bottom of the Truckee River near Squaw Valley, Mar. 17, 2015. Photo: Joanna Rutkowski.

Signal crayfish
Pacifastacus leniusculus
  • Brown/green bodies up to 6 inches long.
  • Two large pincer-claws with a white spot at the joint.
  • Five sets of walking legs.
  • Two long antennae.
  • An invasive species.

Record Observations
Species Description:

There are 315 species of crayfish (crawfish, crawdads) in North America (Voshell 2002), but only one found in the Truckee river, the Signal crayfish (Lawrence & Seiler 2002).  Signal crayfish are native to the Pacific Northwest, including Oregon, Idaho and Washington.  They were introduced to California and Nevada, and today are abundant in Lake Tahoe and the Truckee River.

Crayfish are omnivores, and feed on pretty much everything in the river that can be eaten: decaying plants, live plants, snails, aquatic insects, small fish, fish eggs, and dead fish.  They use their large claws for shredding and ripping, and small claws for finer handling and chopping food.  When disturbed, crayfish use their flipper-like tails to scoot backwards through the water (hint: catch crayfish by putting your net behind them).  Crayfish are most active at night (Voshell 2002).

Female crayfish lay many eggs, and use a sticky substance to attach eggs to the bottom of their abdomen.  Crayfish have large pincer-claws which they use for defense, and walking legs which can be shed to escape the grasp of predators (Voshell 2002).  They are edible by humans, and in 2010, the Tahoe Lobster Company began commercial harvest of crayfish in Lake Tahoe.

Photos & Information needed!

Do you have information on the Signal Crayfish, or original photographs taken locally?  If so, please contribute photos and observations here, or email information to Thanks!



Lawrence, S. J. and Seiler, R.L. 2002. Aquatic Invertebrates, and Fish from Selected Reaches on the Carson and Truckee Rivers, Nevada and California, 1993 – 97.  United States Geological Survey, Open-File Report 02-012.

Voshell, J. Reese., and Amy Bartlett. Wright. 2002. A Guide to Common Freshwater Invertebrates of North America. Blacksburg, VA: McDonald & Woodward Pub.


Share this Project

Leave a Comment

This site uses Akismet to reduce spam. Learn how your comment data is processed.