An invasive species revisited: Continued displacement of native crayfishes by the invasive Faxonius rusticus (Girard, 1852) (Decapoda: Astacidea: Cambaridae) in Illinois after 25 years

Since 1995 Faxonius rusticus () has continued to expand its range in Illinois, USA and cause displacement of native crayfishes. We revisit five historic collection sites for F. rusticus made by C.A. Taylor and M. Redmer in 1995 and compare densities of F. rusticus with native sympatric crayfish species to document changes over the past 25 years. We additionally compiled data from vouchered specimens and update the range of F. rusticus in Illinois. Data from the five density sites indicates that F. rusticus is still common and displacing sympatric crayfish at four of the five sites. Since 1995 F. rusticus has been collected at 137 new sites including range expansions west and south in Illinois. It now has been collected from one-third of Illinois drainages. Recent evidence has provided a cause for optimism as in some areas F. rusticus populations are declining. Without proper monitoring and management F. rusticus will continue to spread in Illinois waters.