Orconectes rusticus (Girard, 1852). Faxonius rusticus underwent a reclassification in August 2017, changing the genus of non-cave dwelling Orconectes to Faxonius (Crandall and De Grave 2017).

Mature rusty crayfish mate in late summer, early fall, or early spring. The female stores sperm transferred from one or more males until its eggs are ready to be fertilized—usually by late spring when water temperatures begin to increase (Berrill and Arsenault 1984). Therefore, it is possible for a single mature female carrying viable sperm to begin a new population if she is released into a suitable habitat. Rusty crayfish females can lay between 80 and 575 eggs (Gunderson 2008). Eggs hatch in three to six weeks depending on water temperature. Juveniles stay with the female for several weeks after hatching (Berrill 1978) and reach full maturity the following year upon completion of about eight to ten molt cycles. After maturity is reached, growth slows greatly, with males typically molting twice per year and females molting once. In the spring, the male molts into a sexually inactive from (Form II) and returns to its sexually active form (Form I) in the summer (Gunderson 2008). The expected lifespan of F. rusticus is 3-4 years.

In its native range within the Ohio River valley, F. rusticus may seasonally be exposed to water temperatures ranging from close to 0°C up to 39°C; however, it prefers water temperatures between 20 and 25°C (Mundahl and Benton 1990). The maximum growth rate of juveniles is thought to occur at water temperatures between 26 and 28°C, while the maximum juvenile survival rate occurs at temperatures between 20 and 22°C. Therefore, adults will often displace juveniles into warmer habitats to favor maximum growth rate as a means of improving fecundity and competitive abilities (Mundahl and Benton 1990). At temperatures greater than 30°C, F. rusticus has been observed digging burrows in the sand beneath rocks near shore as a means of escaping the heat (Mundahl 1989).

Faxonius rusticus individuals feed as shredders, scrapers, collectors, and predators (Lorman and Magnuson 1978). This species is an opportunistic consumer of a variety of aquatic plants, benthic invertebrates, detritus (decaying plants and animals, including associated bacteria), periphyton (algae and microbes attached to objects submersed in water), fish eggs, and small fish (Lorman 1980). Juveniles tend to feed on benthic invertebrates, such as mayflies, stoneflies, midges, and side-swimmers, more often than do adults (Hanson et al. 1990, Momot 1992). Among the options of invertebrate prey for adults, snails are a primary target (Lodge and Lorman 1987).

Summary of species impacts derived from literature review. Click on an icon to find out more...

Environmental	Socioeconomic	Beneficial

Rusty crayfish generally displace crayfish in the Great Lakes region including non-native virile crayfish (F. virilis), and native northern clearwater crayfish (F. propinquus) (Capelli 1982, Butler and Stein 1985, Olsen et al. 1991, DiDonato and Lodge 1993, Taylor & Redmer, 1996, Hill and Lodge 1999 Byron & Wilson, 2001; Garvey et al. 2003, Olden et al. 2006, Hein et al. 2006, Rosenthal et al. 2006, Peters et al. 2008, Hayes et al. 2009; Peters and Lodge 2013, USFWS ERSS 2015, Smith et al., 2019, O’Shaughnessey et al 2021 and Kuhlmann 2021).  In Ohio, it has also displaced F. obscurus, F. sanbornii and F. sloanii (Jezerinac, 1986; Mather & Stein, 1993, USFWS ERSS 2015). Red swamp crayfish (P. clarkii) is a newer crayfish invader to the region, most likely P. clarkii will dominate over F. rusticus in water with low clarity, but not in clear-water habitats where visual predators are more effective (O’Shaughnessey and Keller 2019).   Rusty crayfish also competes with young native gamefish such as bluegill and sunfish (Wilson et al 2004, McCarthy et al 2006).

Faxonius rusticus reduces aquatic vascular plant biomass through both consumption and non-consumptive destruction (Lodge and Lorman 1987); species richness and abundance decline significantly in lakes invaded by F. rusticus (Alexander et al, 2008; Rosenthal et al, 2006; Roth et al, 2007; Wilson et al, 2004).  F. rusticus invasion also results in reductions to the abundance and diversity of macroinvertebrates including snails (especially smaller native species), young native unionid clams, larval midges, mayflies, dragonflies, stoneflies, amphipods (Charlebois and Lamberti 1996, Lodge et al, 1998, Wilson et al. 2004, Klocker & Strayer, 2004, McCarthy et al. 2006, Kuhlmann & Hazelton, 2007, Bobeldyk and Lamberti 2008, Johnson et al. 2009, Kuhlman 2016, Szydlowski et al. 2022). While edible to native fish species, the Rusty crayfish provides a lower quality of food compared to the benthic invertebrates and insects it replaces (Gunderson 2008). Faxonius rusticus also stimulates increased fish predation on native crayfish species, as it forces native crayfish from the best hiding places and leaves them vulnerable to attack. In experimental trials, rusty crayfish were efficient predators on juvenile Lake sturgeon (Acipenser fulvescens) - additionally, when the sturgeon responded by moving to avoid crayfish predation, they became more vulnerable to fish predators (Crossman et al 2018). Another threat posed to fish populations by this species is the consumption of fish eggs (Dorn and Mittelbach 2004, Horns and Magnuson 1981, Kreps 2009, McBride 1983) including eggs of Lake sturgeon (Forsythe et al 2018).

F. rusticus has been demonstrated to hybridize with both F. propinquus (Berrill 1985, Capelli and Capelli 1980, Page 1985. Perry et al 2001) and F. obscurus (Merovich et al 2022).

Faxonius rusticus has a moderate socio-economic impact in the Great Lakes outside of its native range.

While an official study has not yet been conducted, personal observations of fisheries managers have suggested frequent decline of bluegill (Lepomis macrochirus), northern pike (Esox lucius), and bass (Micropterus spp.) populations following the introduction of F. rusticus.  F. rusticus is more likely to compete with juvenile gamefish for benthic invertebrate prey than are native species of crayfish and have been shown to significantly reduce benthic invertebrate densities that serve as an important food source to young fish (Bobeldyk and Lamberti 2008, Hill and Lodge 1995, Lodge et al. 1994, Luttenton et al. 1998, Magnuson et al. 1975, McCarthy et al. 2006, Rosenthal et al. 2006).  While native fish do feed on the non-native F. rusticus, due to its low ratio of soft tissue to hard exoskeleton, F. rusticus provides a lower quality of food than many of the native invertebrate species it replaces. This leads to slower fish growth and reduced survival (Gunderson 2008).  F. rusticus has also been seen to prey on a variety of fish eggs (Dorn and Mittelbach 2004, Kreps 2009, Baldrige and Lodge 2013). F. rusticus introduction is also believed to reduce sport fish populations especially pan-fish (Lepomis macrochirus and L. gibbosus) by either egg predation or competition with juveniles. Researchers have calculated fisheries damages of F. rusticus in Vilas County, Wisconsin to be about $1.5 million annually (Keller et al, 2008, USFWS ERSS 2015).

F. rusticus creates turbidity in its environment that results in an increase of harmful algae blooms by changing the water chemistry (Welch 2014). Periphyton productivity showed a 4 to 7 fold increase in enclosures where F. rusticus were present, likely due to the indirect effect of reduced macroinvertebrate grazer densities and the direct effect of the reduction of non-photosynthetic portions of the periphyton matrix (Charlebois and Lamberti 1996).

Due to its conspicuousness during daylight hours relative to native crayfish species, F. rusticus has resulted in a decline in recreational swimming in areas where present, as swimmers fear stepping on it and being pinched by its large claws (Gunderson 2008).

Faxonius rusticus has a moderate beneficial impact in the Great Lakes outside of its native range.

Faxonius rusticus has been intentionally established in some lakes as a means of removing nuisance weeds (Magnuson et al. 1975). It has been shown to effectively control weeds in many northern Wisconsin lakes (Capelli 1982a, Lorman and Magnuson 1978, Magnuson et al. 1975, USFWS ERSS 2015).  F. rusticus is also commonly sold to schools and biological supply houses (Gunderson 2008) as well as for bait (Wilson et al 2004, USFWS ERSS 2015). F. rusticus is eaten by many species of fish (Roth and Kitchell 2005, Capelli 1982) and wildlife including endangered hellbenders (Cava et al 2018, Hartzell et al 2021).

It is illegal to possess, sell, purchase, offer for sale or barter, transport, import, or introduce this species to Pennsylvania (PAFBC 2006a, b, c), Michigan (Michigan 1994, MIDNR 2004), and Illinois (ILDNR 2005). In Minnesota, the Rusty crayfish is listed as a regulated invasive species, making it illegal to introduce (i.e. release live) or sell live in that state (MORS 2008). A similar classification in Wisconsin prohibits release of any crayfish into the waters of that state, as well as simultaneous possession of both live crayfish and angling equipment on inland waters other than the Mississippi River (WIDNR 2004).

In Ontario, live crayfish may only be used as bait in the waters from which they were caught; they may not be transported overland, including importation for use as bait, nor may they be sold or purchased if recreationally caught (OMNR 2011).

Preemptive legislation has prevented rusty crayfish spread through anthropogenic transportation (Dresser and Swanson 2013).

Note: Check federal, state/provincial, and local regulations for the most up-to-date information.

Control

Biological
It is suggested that by restoring healthy populations of bass and sunfish, the effects of rusty crayfish may not be as severe (Momot 1984). In an experiment where regulations were put into effect to protect a smallmouth bass population, aquatic plants, benthic invertebrates, and sunfish all experienced population increases due to the increased predation pressure of the smallmouth bass on F. rusticus (Hein et al. 2006, Hein et al. 2007). It has also been suggested that total crayfish consumption, rather than proportion of a diet (Dorn and Mittelbach 1999), is more important when selecting a proper fish species as a control agent, and that different life stages of fish are more effective at different times in the control of F. rusticus (Peters 2010).

Physical
The establishment of electric fences to protect macrophyte populations from the rusty crayfish has significantly reduced crayfish densities in experimental plots (Peters et al. 2008). However, even at these reduced densities, F. rusticus was able to eliminate selected native plant species within three weeks, compared to within a matter of days in the control plots (Peters et al. 2008).

Intensive harvest may reduce adult rusty crayfish populations, but will not lead to complete eradication. Therefore, manual removal, proper fishery management, and prevention of its introduction to new areas are the most valuable tools for minimizing the wide-ranging negative impacts of F. rusticus.

Chemical
While many chemicals are available to selectively kill crayfish, none is currently registered specifically for crayfish control (Ray and Stevens 1970, Bills and Marking 1988).

Other
The most important method of control remains education of anglers, crayfish trappers, bait dealers, and the public about the numerous threats this species presents to the Great Lakes and what they can do to prevent its expansion. Moreover, the Michigan Department of Natural Resources (2012) suggests harvest for culinary use as a potential control mechanism.

Faxonius rusticus underwent a reclassification in August 2017, changing the genus of non-cave dwelling Orconectes to Faxonius (Crandall and De Grave 2017).