Coping with the Invasive Rusty Crayfish in the Chicago Region

The Chicago Region is home to four native fully aquatic crayfish species, the calico (Orconectes immunis), virile (Orconectes virilis), northern clearwater (Faxonius propinquus) and white river crayfish (Procambarus acutus) (IDNR). These species of crayfish would have a higher population, if it weren’t for the two invasive species that currently reside in the region. The invasive red swamp crayfish and the invasive rusty crayfish compete with the native species, though, the rusty crayfish is the most dominant (Rosalie & Keller, 2018). Due to their aggressive nature, Rusty crayfish (Faxonius rusticus) are known to dominate the suitable habitat in diverse bodies of freshwater compared to other species of crayfish. These crayfish have been invading Chicago freshwater regions since 1973, so how did they become invasive, and what can we do about it?

The rusty crayfish is originally native to areas like Indiana, western Ohio, and northern Kentucky. They were naively introduced by anglers when emptying their bait buckets into bodies of freshwater. This species of crayfish is a popular source of bait to catch freshwater fish, as many species of large freshwater fish prefer to eat these crayfish. Under the Illinois Fishing Regulation of 2025, Rusty crayfish are illegal to use as live bait, though can be used as bait when deceased. Additionally, they were purposefully introduced as a means to attempt to control aquatic weeds that were deemed a nuisance. Rusty crayfish were also commonly sold to schools and biological supply houses, which ultimately resulted in people introducing them to lakes and rivers as well (Donahou et al, 2024). These three introduction routes have resulted in rusty crayfish moving into 20 states and in parts of southern Canada, meaning their current range has doubled in size according to the USGS.

Rusty Crayfish (Faxonius rusticus) Native and Introduced Range

Rusty crayfish function as both predators and decomposers in the ecosystems in which they live. They eat anything from small fish and invertebrate larvae to aquatic plants, decaying plants, fish eggs, and even other crayfish. Their presence impacts the entire ecosystem by lowering the populations of fish and invertebrates such as mayflies and stoneflies. The aggressive behavior of the rusty crayfish and its competition for shared, limited resources causes a problem for less-aggressive native crayfish species. This is an example of interspecific competition where the invasive species negatively impacts the abundances of native competitor species. Rusty crayfish can produce between 80 to 575 eggs annually. The eggs take around three to six weeks to gestate, and the adult crayfish can live up to four years. With consistent reproduction every spring and their aggressive behaviors, these crayfish have been successfully expanding their range and abundance in most places where they have been introduced.

Our goal as conservation biologists is to curb the rusty crayfish's population growth, even if they never will be fully eradicated from places where they have been established. This will allow the opportunity for our native crayfish to live more easily in their regions again.

Familiarize yourself with the fishing regulations so you can help achieve our goal:

1. The first step is to be able to identify a rusty crayfish. They have a more grayish-greenish color that contrasts differently from the colors that native crayfish typically have. Most importantly, they have a signature dark red rusty spot on both sides of their carapace.

Identifying Field Marks of the Rusty Crayfish (image from https://www.invasivespeciescentre.ca/)

2. If you identify a rusty crayfish, do not throw it back into the water, and do not release it into a different ecosystem - this is illegal and can result in a fine.

3. You are allowed to use rusty crayfish as fishing bait if they are dead before baiting your hook. You can have a maximum of 36 crayfish with you at a time in most states where they are a target of invasive species management.

4. If you spot a rusty crayfish and do not plan to use them as bait, you can contact the Invading Species Hotline at 1-800-563-7711 and notify them. You can also use this hotline to report anyone who is violating the Illinois rusty crayfish laws (Illinois Department of Natural Resources, 2025).

5. As a general reminder, never release live bait into bodies of water - no matter the species of organism. This can introduce dangerous diseases, parasites, or introduce non-native species such as the rusty crayfish.

6. Educate your friends and family to help limit their spread!

Here at Oakton College, we are aware of the presence of rusty crayfish in Lake Oakton. Our first priority when it comes to this species is to help reduce the population of these crayfish. Our second priority is to educate our larger community about these efforts and why they are important to local biodiversity. My project involves engaging in community outreach in multiple programs, such as Oakton’s annual open house where we brought live rusty crayfish for display and educated people about the species and why they are invasive. This topic has also been the focus of two sessions during the community-wide Earth Month events hosted and organized by Oakton in April 2025. These outlets represent new educational opportunities aimed at a broader audience compared to the more limited population of students taking our environmental science course.

In addition, when we obtain rusty crayfish during labs, we refrain from returning them back into the lake. Instead, we can opt to donate them as feeding enrichment for the animals at the nearby The Grove Nature Center or keep and utilize them as educational resources for our community events and classes.

Removing Rusty Crayfish from Lake Oakton via Minnow Traps

In the future, we hope to keep the rusty crayfish population in decline by publicly educating anglers about being responsible with their bait. One way we can help anglers become educated about the rusty crayfish on campus is by placing a permanent ecological interpretative sign by Lake Oakton which includes a warning regarding invasive species. This will hopefully teach people about the risks of throwing live bait or rusty crayfish back into the water. Down the line we might even be able to reintroduce native crayfish species to our lake! Stay tuned as we attempt to manage this invasive species in Lake Oakton.

-- Fatima Elgarawany