The first occurrence of the southern plains crayfish Procambarus simulans (Faxon, 1884) documented in Montana, USA

During a statewide crayfish survey of Montana, we documented the southern plains crayfish Procambarus simulans for the first time in the state. Procambarus simulans is native to, and commonly found in, southern and central US states, including Arkansas, Colorado, Kansas, Louisiana, New Mexico, Oklahoma, and Texas. We found this species in a single location, the Miles City State Fish Hatchery, in eastern Montana. At 46.38 degrees north latitude, this is the northernmost population of the species reported. The presence of multiple size classes suggests that the crayfish can overwinter and reproduce in Montana and have been at the location for at least several years. The source of introduction, current extent of spread, and ecosystem impacts are unknown, and investigation is needed to understand the source and effects of this novel species on native crayfishes and other aquatic species.