Faxonius rusticus has a high environmental impact in the Great Lakes outside of its native range. 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).