Range expansion of the invasive rusty crayfish Orconectes rusticus (Girard, 1852) (Decapoda: Astacoidea) in northeastern Iowa (USA) rivers.
The rusty crayfish Orconectes rusticus (Girard, 1852) is an invasive species that has been introduced to the Upper Midwest, USA from the Ohio River Valley, and is associated with ecological damage to aquatic systems. We examined the distributions of rusty and native crayfishes in two Iowa river systems. One hundred sites were surveyed in the upper Cedar and middle Wapsipinicon river drainages from 2013 to 2014. Four native crayfish species were collected, and contrary to a study conducted in 2002, the rusty crayfish was documented in the mainstream of both systems. Analysis of sampling methods indicates that crayfish capture rates were significantly higher in cylindrical minnow traps than in flat crayfish traps. Genetic analyses confirmed field identifications and support a single introduction of the rusty crayfish in northeastern Iowa. The pervasive distribution and life history characteristics of the rusty crayfish suggest that eradication is currently not feasible. Further monitoring is warranted in order to determine its distribution throughout Iowa's river systems.