Most of our crustacean friends– crabs, lobsters, and their kin– call the sea their home. But a few adventurous groups of these hard-shelled, many-legged invertebrates left the sea long ago to take up residence in freshwaters.
The most familiar of the freshwater crustaceans are the crayfish (also called crawdads or crawfish). Of course, crayfish are not fish, but are close relatives of the ocean-dwelling lobsters.
Crayfish creep along the bottom of streams, rivers, lakes, ponds, and swamps, using their claws (the technical terms for a claw is chela, or plural chelae) to pick apart and eat dead and living plants and animals. Crayfish are eaten in turn by predators, such as raccoons and birds. Their roles as consumers and as prey make crayfish important parts of freshwater ecosystems.
There are about 350 crayfish species in the United States, some of which are famous for their tendencies to end up in the cooking pots of folks in Louisiana. Crayfish are also used as live bait by fishermen across the country.
What’s the Deal with Crayfish in Washington and Oregon?
When you see a crayfish in the Pacific Northwest, it might be a native species (awesome!) or it could be an invasive species (bummer!).
The most widespread native species in the northwest is the Signal Crayfish (Pacifastacus leniusculus). Signal Crayfish come in a variety of colors: bright red, dull green-brown, or even bluish. They seem to prefer swiftly flowing waters, rather than lazy pools.
This species can be found throughout Washington and Oregon– from the coastal streams to the rivers of the Columbia Basin.
Recent research based on genetic data found that what we call the Signal Crayfish may actually represent four distinct species, each found in a different part of the northwest:
- The Olympic Peninsula and Puget Sound area
- The Okanagan Highlands
- Central Oregon
- Everywhere else that the Signal Crayfish lives (but it has been introduced here and there as well)
An invasive species that you might mistake for a Signal Crayfish is the Red Swamp Crayfish (Procambarus clarkii). The latter is the one most often eaten by people. The main way to tell the two species apart is to look at the texture of the ‘shell,’ which is the animals’ exoskeleton, called a carapace. If your crayfish’s carapace is covered with red, white, or dark bumps, you probably have a Red Swamp Crayfish.
The Rusty Crayfish (Orconectes rusticus) is another invasive species that can look like a Signal Crayfish. Rusty Crayfish have a large, rust-colored spot on both sides of their carapace.
The only other native species found within the borders of Washington and Oregon is the Snake River Pilose Crayfish (Pacifastacus connectens). This species lives in southeastern Oregon and Idaho, in desert lakes and in streams that drain into the Snake River. Not much is known about how this animal makes a living or about the status of its populations.
There are six invasive (i.e. alien) crayfish species that have been found in the Pacific Northwest, including the Red Swamp Crayfish and the Rusty Crayfish.
How did these invaders get here? They have gills and must be in water to survive, so they sure didn’t crawl over land (although they can crawl short distances over land).
It is humans who move crayfish from place to place, all across the planet, both intentionally and accidentally, for eating and for use as bait. Even our own Signal Crayfish has been introduced to Europe, Japan, and elsewhere!
Live crayfish have been used in elementary and high school science classes for years. The animals are shipped from biological supply companies. Many compassionate kids have opted to ‘free’ their little study animals into local streams or ponds, rather than kill them. Unfortunately, once they are turned loose, these non-native crayfish can cause a lot of damage.
The problem with invasive crayfish is that they often crowd out and outcompete the natives. They sometimes kill and eat other native animals or plants.
I look forward to returning to the Drift Creek Wilderness in Oregon, where I have seen many native Signal Crayfish in the stream. I took the photo at the top of this post at Drift Creek. In case you were wondering: I didn’t leave the energy bar wrapper in the wilderness