Crayfish, sometimes called “crawdads” or “crawfish,” are small lobster-like animals that live in freshwater streams, ponds, lakes, swamps, and marshes throughout the world. There are about 600 species worldwide, and nearly 65 percent of those species inhabit waters in the United States.
Crayfish are thought to represent one of the most important links in food webs because of their diverse, omnivorous diets and that they are eaten by many other animals such as fishes and birds. In fact, over 240 species of animals in North America have been found to eat crayfish.
People also eat a lot of crayfish, specifically the red swamp crayfish, Procambarus clarkii. The commercial value in the food industry (especially live crayfish) represents hundreds of millions of dollars annually in Louisiana alone.
The red swamp crayfish is approximately 2 to 4.5 inches long, usually dark red, and has an elongate head and claws; the claws have bright rows of red bumps. To distinguish it from the native white river crayfish (Procambarus acutus), examine the curved lines on the crayfish's backs. The red swamp crayfish’s lines touch while the white river crayfish’s lines remain separated.
The red swamp crayfish is native to the southern United States and northeastern New Mexico but has been introduced to every continent except Antarctica and Oceania (i.e., Australia, Melanesia, Micronesia, and Polynesia); thus, they are considered the most cosmopolitan freshwater crayfish species and one of the most well known invasive species in the world.
In Illinois, red swamp crayfish are native to the southern tip of the state but have been found much farther north. Until recently, red swamp crayfish were restricted to the North Branch of the Chicago River and the Illinois and Michigan canal. In 2019, several individuals were found in the Chicago Sanitary and Ship Canal within the Lockport Pool, which is directly connected to the Illinois River.
The continued expansion of red swamp crayfish could be damaging to many of the 23 crayfish species native to Illinois, of which four are already listed as state endangered.
Non-native crayfishes often outcompete native crayfish for food and resources, not to mention native crayfishes already are facing issues such as habitat destruction from dams, water pollution, etc.
What can you do to help?
Be on the lookout for the red swamp crayfish! Know how to identify it and report any observations to your local environmental agency!
