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).

Great Lakes Occurrences (outside of native range):

Faxonius rusticus was first seen in the Great Lakes near the mouth of the Maumee River, Ohio in the early 1800s (Perry et al. 2002). It likely migrated across the low, swampy barrier between the Maumee drainage and the Scioto or Wabash River drainages, or traveled through a canal built in the early 1800s that connected these drainages (Creaser 1931). Faxonius rusticus has been found in the Lake Michigan drainage in Indiana, outside of its native range of the Whitewater River drainage (Simon 2001). Nonindigenous populations are now established in Green Bay and along the entire eastern shore of Lake Michigan from Indiana to Grand Traverse Bay, including the St. Joseph River (Perry et al. 2002). This species was first observed in Lake Huron in 1998, collected from the Carp-Pine drainage in Mismer Bay and Cedarville Bay, Mackinac County, Michigan (Albert et al. 1999). In 2001, abundant mature specimens of F. rusticus were collected surrounding the Les Cheneaux Islands in Lake Huron, on the southeastern shore of the Upper Peninsula. In 1997, specimens were collected near Tischer Creek in St. Louis County, Minnesota, a steam that drains into Lake Superior. The first established occurrence of the species within Lake Superior dates to when it was collected from St. Louis Bay at the Minnesota Power M.L. Hibbard Steam Electric Station, St. Louis County, Minnesota in 1999 (Rodd 1999). Again, in September 2001, the rusty crayfish was collected from the Western Lake Superior drainage in Cook County, Minnesota. For over a decade, F. rusticus has exerted persistent negative impacts on the middle branch of the Ontonagon River, which flows into Lake Superior (Bobeldyk and Lamberti 2008). The most recent report of this species in Lake Superior was in May 2007, when it was observed in Douglas County, Wisconsin.

In Ontario, F. rusticus has invaded many lakes and streams. It has been in Lake of the Woods, Ontario, since the mid-1960s (Crocker and Barr 1968, in only four or five waterbodies within the Thunder Bay district, and in Lake Superior and some of its tributaries (Momot 1996). Faxonius rusticus was first recorded in Whitefish Lake during the fall of 2003 (Amtstaetter 2008).

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).

Its status is unknown in Massachusetts, New Hampshire, and Tennessee, as the only reported introductions are from Hobbs (1989).

Extirpated in Wyoming (Wyoming Game and Fish Department 2015).

Potential:
Current research suggests that the rusty crayfish could have a variety of negative environmental impacts if it continues to expand its range within the Great Lakes. Crayfish in general are considered to be ecosystem engineers, as they have a wide variety of indirect effects on ecosystems through disturbances, such as bioturbation (Jones et al. 1994, Statzner et al. 2000, Crooks 2002, Creed and Reed 2004, Usio and Townsend 2004, Zhang et al. 2004, Kuhlmann and Hazelton 2007). Native and/or existing species of crayfish are at risk of being displaced by this aggressive species (Magnuson et al. 1975). Replacement of low densities of native F. propinquus by higher densities of F. rusticus is expected to have many widespread negative effects on aquatic communities (Kuhlmann and Hazelton 2007). Displacement of F. virilis and F. propinquus has already occurred in many Northern Wisconsin lakes and in lakes throughout Ontario due to the introduction of F. rusticus. These kinds of species displacements have been observed wherever the rusty crayfish has been introduced (Capelli 1982, Butler and Stein 1985, Lodge et al. 1986, Olsen et al. 1991, Hill and Lodge 1994, Olden et al. 2006). Evidence of the rapid dominance of this species over previously established crayfish species was seen in a recent study on Lake Ottawa in Michigan’s Upper Peninsula. Rusty crayfish were first noticed in the lake in 1987, where it made up about 20% of the crayfish community. By 1997, it had begun to dominate, making up 75% of the crayfish population, and since 2001 it has accounted for 100% of the crayfish species caught in traps (Rosenthal et al. 2006, Peters et al. 2008). There are three primary mechanisms through which the rusty crayfish is able to displace resident species.

One mechanism of species displacement is crayfish-to-crayfish competition, as this species is better able to compete for food resources and space than are many other species (Garvey et al. 1994, Hill and Lodge 1994, Bobeldyk and Lamberti 2008). Although both the rusty and native species of crayfish feed on aquatic plants, the rusty crayfish has a higher metabolic rate and spends less time hiding from predators, meaning it will eat more and spend a greater amount of time feeding (Stein 1977, Jones and Momot 1983). Due to its higher metabolic rate, F. rusticus is believed to consume twice as much daily as similarly-sized native crayfish (Olsen et al. 1991, Momot 1992).

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 addition, the rusty crayfish has larger claws than the majority of native species and is therefore better able to avoid predation (DiDonato and Lodge 1993, Hill and Lodge 1993, Garvey et al. 1994, Roth and Kitchell 2005).

The final mechanism of resident crayfish displacement is the ability of F. rusticus to hybridize with the native clearwater crayfish, F. propinquus (Capelli and Capelli 1980, Berrill 1985, Page 1985). Hybridization has been observed in locations spanning most of the eastern shoreline of Lake Michigan, with F. rusticus males able to outcompete F. propinquus males for F. propinquus females (Perry et al. 2002). In a 1980 study, over 25% of the crayfish individuals collected from several northern Wisconsin lakes showed characteristics of hybridization between F. rusticus and F. propinquus (Capelli and Capelli 1980). This results in competitive superiority of the hybrids and ultimately excludes genetically pure F. propinquus faster than F. rusticus could alone (Hill and Lodge 1999, Perry et al. 2001a, b). Again in a more recent study, about 25% of the crayfish collected from lakes in northern Wisconsin showed genetic evidence of hybridization between the northern clearwater and the rusty (Perry et al. 2001b).

Further shifts in predator-prey/grazer-vegetation relationships stem from the reduction of aquatic plant abundance and diversity in areas where this species has been introduced (Lodge and Lorman 1987, Olsen et al. 1991, Lodge et al. 1994, Momot 1995, Rosenthal et al. 2006, Wilson et al. 2004, Bobeldyk and Lamberti 2008). Destruction of aquatic plant beds is thought to be one of the most serious environmental threats that F. rusticus presents. Submerged plants are vital to aquatic systems, as they provide a habitat for benthic invertebrates, shelter young gamefish, provide fish with a nesting substrate, and control erosion through stabilization of the sediment and by minimizing wave energy. Reduction in macrophyte habitat may lead to negative effects on fish populations (Rosenthal et al. 2006), as well as profound effects on the energy transfer between trophic levels in a system (Kreps 2009). In the northern Great Lakes, where plant density is relatively low, herbivory on beneficial aquatic plants may be a particularly acute threat, heightening the concern of rusty crayfish range expansion to these lakes. In a study conducted on the effects of F. rusticus on benthic invertebrates and periphyton in a northern Michigan stream, it was observed that this species reduced macroinvertebrate densities by 47-58% and herbivore densities by 55-72% in stream enclosures relative to exclosures (Charlebois and Lamberti 1996). In the same study, 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). Resulting algal blooms in invaded areas are likely the result of the crayfish being a much less efficient grazer than the macroinvertebrates it replaces (Lodge et al. 1994, Luttenton et al. 1998, Kreps 2009).

A long-term study demonstrated that fish species that compete for prey with F. rusticus, such as bluegills and sunfish, experience population decline over time after the introduction of the rusty crayfish to their environment (Wilson et al. 2004). Reduction in the total quantity of zoobenthos, larval midges, mayflies, dragonflies, and stoneflies has been observed with the presence of rusty crayfish populations, reducing yet another food source of young native gamefish (McCarthy et al. 2006). 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). Another threat posed to fish populations by this species is the consumption of fish eggs, specifically trout (Horns and Magnuson 1981, McBride 1983, Dorn and Mittelbach 2004, Kreps 2009,). The pumpkinseed has been shown to do an especially poor job of defending its eggs from crayfish attack (Wilson et al. 2004).

It has also been observed that lakes and streams containing F. rusticus populations may experience slower colonization by and lower overall densities of invasive zebra mussels than systems lacking crayfish, although it is unlikely that these crayfish can reduce zebra mussel populations below levels that are ecologically important (Perry et al. 1997). Alternatively, the introduction of rusty crayfish to lakes and streams in the Northeast has caused significant population declines in native unionid mussel populations (Klocker and Strayer 2004); a similar effect could be seen in the Great Lakes. Zebra mussels have also been observed colonizing most of the bodies of rusty crayfish specimens collected from Green Bay in 1995, with up to 431 mussels attached to a single crayfish (Brazner and Jensen 2000). Mussel colonization on crayfish is greatest in areas of soft substrate, as there are limited alternate hard surfaces on which the mussels can settle. In previous studies examining the effects of zebra mussel colonization on native unionids, it was found that mussel densities of between 100 and 200 per native unionid and over 5000 zebra mussel per m² led to very high mortality rates in the native unionids (Schlosser et al. 1996). As these zebra mussel densities are present in areas concurrently inhabited by rusty crayfish, it is hypothesized that these same negative effects may be observed on crayfish populations as well (Brazner and Jensen 2000).

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

Potential:
Faxonius rusticus has the ability to cause a reduction in many native fish populations, creating a variety of negative socio-economic impacts. The rusty crayfish is more likely to compete with juvenile gamefish for benthic invertebrate prey than are native species of crayfish. In addition, this species has been shown to significantly reduce benthic invertebrate densities that serve as an important food source to young fish (Magnuson et al. 1975, Lodge et al. 1994, Lodge 1995, Hill and Luttenton et al. 1998, McCarthy et al. 2006, Rosenthal et al. 2006, Bobeldyk and Lamberti 2008,). While native fish do feed on the non-native rusty, 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). The rusty crayfish has also been seen to prey on a variety of fish eggs, specifically those of trout (Dorn and Mittelbach 2004, Kreps 2009). While an official study has not yet been conducted, personal observations of fisheries managers have suggested frequent decline of bluegill, northern pike, and bass populations following the introduction of rusty crayfish.
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.

Potential:
Angler bait bucket emptying is thought to be the primary vector of introduction and species spread (Berrill 1978, Crocker 1979, Butler and Stein 1985, Lodge et al. 1986, Lodge et al. 1994, Kerr et al. 2005), which suggests that this species may have value as a recreational bait species in the Great Lakes. The rusty crayfish is also commonly sold to schools and biological supply houses (Gunderson 2008). Intentional release into water bodies by commercial crayfish harvesters is another suspected cause for its expanded range (Wilson et al. 2004), reflecting its commercial value. Moreover, this species 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 (Magnuson et al. 1975, Lorman and Magnuson 1978, Capelli 1982), and residents have noticed a great decline in the number of aquatic weed beds in the area ever since the rusty crayfish population began to reach a tremendous size (Hobbs et al. 1989).

Regulations (pertaining to the Great Lakes region):

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).

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