Species of Concern

Photographer: National Park Service

The invasive rusty and red swamp crayfishes currently are the species of primary concern for the Great Lakes Region. Ongoing work of the ICC involves identification of additional species that may prove to be a threat to the Region.

Rusty crayfish (Faxonius rusticus)

Identification

Photographer: Paul Skawinski, University of Wisconsin - Stevens Point (UWSP)

Rusty crayfish are typically olive green to gray in body color, with larger individuals sometimes possessing chelae (claws) with light blue or violet hues and black rings around the tips of the dactyls (fingers). Note—some other species also have black rings around the tips of the dactyls. Most notably, rusty crayfish have two unique ‘rust’or brown-colored spots on each side of the posterior margin of their carapace (cephalothorax). No other crayfish species in the Great Lakes Region possess these unique spots on the carapace.

Spread

Rusty crayfish are native to portions of Indiana and Ohio, although they have expanded their range dramatically to now include most of the upper Midwest, including portions of Canada. Isolated, introduced populations now exist as far west as Oregon and as far east as Maine. Rusty crayfish may have expanded their range due in part to the artificial connection of waterways (via canals) in the upper Midwest and Great Lakes regions throughout the 19th and 20th centuries (Creaser, 1931), and sporadic anthropogenic translocations and introductions may have further facilitated their rapid range expansion. Rusty crayfish are also tolerant to a wide variety of habitat conditions, and they appear to survive well in many habitat types, including lakes, ponds, streams, and rivers (Taylor and Redmer, 1996). In addition to their apparent adaptability, rusty crayfish also grow larger and can be more aggressive than similar congeneric species (Roth and Mitchell, 2005), which may partially explain their ability to displace some native crayfishes.

Distribution

Native to Ohio River basin and parts of Kentucky, Indiana, Tennessee, and Illinois, the rusty crayfish range has expanded and now includes all the Great Lakes states, parts of New England and the mid-Atlantic states, and regions of  Ontario, Canada. It is also present in several western states including Wyoming, Colorado, Nevada, and Oregon.

View a USGS map of Rusty Crayfish distribution in the US.

Red swamp crayfish (Procambarus clarkii)

Identification

Photographer: Paul Skawinski, University of Wisconsin - Stevens Point (UWSP)

Adult red swamp crayfish can be easily identified by their brick red (although sometimes lighter or darker) body coloration, but juvenile red swamp crayfish can be seen in a variety of tan or brown shades and can be freckled with small, dark spots of pigmentation. In addition to their unique coloration, red swamp crayfish differ from most other crayfish species found in the Great Lakes Region by possessing chelae (claws) that are long, slender, and contain multiple small tubercles on the dorsal surface. These tubercles often extend onto the carapace (cephalothorax). The native white river crayfish (Procambarus acutus) can be easily confused with the red swamp crayfish, although the red swamp crayfish has a closed areola, meaning that the two lines on the dorsal surface of its carapace are touching in the middle. Conversely, white river crayfish possess an open areola, meaning that these lines are always visibly separated. Note—alternate color morphs of red swamp crayfish exist in the pet trade, usually consisting of blue or orange hues.

Spread

Photographer: Justin Watt (CC BY 3.0)

Red swamp crayfish are among the most popular and frequently cultured crayfish species in the world, and they are commonly encountered in the bait, aquaculture, and pet trade industries (Taylor et al., 2015). This may be due in part to their popularity as a food item in the southern United States, or perhaps their relative ability to tolerate a variety of different habitat types and conditions. There are also unique color morphs of the species that can be encountered in the pet trade, which make red swamp crayfish a popular species with aquarium hobbyists. Red swamp crayfish have been translocated and introduced around the world, with many isolated populations existing in the Great Lakes and surrounding areas. Red swamp crayfish have been particularly detrimental in Europe, where they have contributed to the extirpation and decline of multiple native European crayfishes by exposing these crayfishes to crayfish plague, a highly infectious disease.

Distribution

Native to the south-central United States along the Gulf Coast and along the Mississippi River basin as far north as southern Illinois, the red swamp crayfish is now in several of the other Great Lakes, mid-Atlantic and far western. Populations have also been reported from Idaho, Utah, Arizona, South Dakota, Nebraska and Georgia.

View a USGS map of Red Swamp Crayfish distribution in the US.