Crayfishes of the New River watershed and Factors Affecting Their Distributions

Crayfishes are keystone species within aquatic ecosystems and many species require conservation efforts to support their continued persistence. Unfortunately, we lack basic data needed to make effective conservation decisions for many crayfishes, especially those that occur in the New River watershed (hereafter New River). Therefore, we investigated coarse-scale drivers of crayfish occurrence in the New River. We used generalized linear mixed effects models to predict occurrence of eight taxa based on instream and landscape-scale environmental data and biotic interactions. There are at least 10 species of crayfishes that occur in the New River. Faxonius cristavarius, F. virilis, Cambarus appalachiensis, and C. chasmodactylus are found in larger tributaries throughout the New River. The following species occupy smaller tributaries of the New River: F. spp. (either F. sanbornii or F. obscurus), C. aff. robustus, C. cf. bartonii, and C. smilax. We found that increasing anthropogenic disturbance led to declines in F. spp., C. cf. bartonii, and C. smilax but had a positive relationship with F. cristavarius. The presence of the potentially invasive species, F. cristivarius, was negatively associated with most species. Embeddedness, substrate, proportion riffle habitat, and lithology were additional variables that structured crayfish assemblages. Our results reveal that increasing human-mediated changes and invasive crayfishes threaten the persistence of native crayfishes in the New River.