Drivers of the Distributions of Stream-Dwelling Crayfishes in the New River Catchment, United States

Crayfish are keystone species and ecosystem engineers in aquatic ecosystems, and many species require conservation to support their continued persistence. Unfortunately, managers often lack basic data needed to make effective conservation decisions. This lack of data is especially true within the New River catchment, United States, where there are 12 known crayfish species, but it is unclear which of those species are native to the catchment, and there is scant ecological and life history data available for many species. Therefore, our objective was to investigate coarse-scale occurrence drivers of crayfishes in the New River catchment. We used generalized linear mixed effects models to predict occurrence of eight taxa based on instream and landscape-scale environmental data and biotic interactions. We found that increasing anthropogenic disturbance led to declines in Faxonius spp. (either Faxonius obscurus or Faxonius sanbornii but could not be identified to species) and Cambarus smilax. In contrast, disturbance had a positive relationship only with Faxonius cristavarius. The presence of F. cristavarius was negatively associated with most species. Embeddedness, substrate, per cent riffle, stream size and lithology were additional variables that were related to crayfish occurrence. Our results reveal that increasing human-mediated changes and invasive crayfish species threaten the persistence of native crayfishes in the New River catchment.