An analysis of suspected crayfish invasions in Missouri, USA: evidence for the prevalence of short-range translocations and support for expanded survey efforts

Reports of alien crayfish invasions are increasingly common and often associated with well-documented ecological effects including native crayfish biodiversity declines. Because most regions in the U.S. and Canada have not been surveyed to detect the presence and gauge the threat status of such invasions, management agencies lack information on the magnitude of problems in their respective jurisdictions. Our objectives were to catalog, confirm and summarize suspected crayfish invasions that were reported in one U.S. state in recent years. Data were also examined for potential spatial patterns, prevalence of certain species as invaders and effects to native crayfishes. We collected reports of crayfish introductions/invasions from 1998-2014, and attempted to confirm them via sampling. We catalogued 34 reports and confirmed 31 as suspected invasions involving 6 invading species. Procambarus acutus was easily the most frequent invader, and all invading species were native to at least part of Missouri. Most suspected invasions involved species that were legal for commercial sale in the state, but many also involved non-commercial species that are described as narrow-range endemics. Invading species were abundant, dominating crayfish communities, at several sites. Native species have apparently declined or been displaced at several locations. Our results suggest the potential for many unreported crayfish invasions in the U.S. and Canada, including those caused by shorter-range (e.g., intrastate) translocations. Ecoregions featuring high crayfish diversity could be threatened with significant declines of native species with narrow ranges. Increased survey efforts in these regions are warranted to estimate threat levels and provide agencies with information to support management actions.