Riverscape correlates for distribution of threatened spotfin chub Erimonax monachus in the Tennessee River Basin, USA

Globally, aquatic biodiversity is imperiled at an increasing rate, especially in diversity hotspots such as the southeastern USA. The spotfin chub Erimonax monachus is a federally threatened minnow with a disjunct distribution resulting from numerous impoundments on the Tennessee River and its tributaries in the heart of the southeastern USA. Recovery actions required to remove federal protection for E. monachus are dependent on the establishment of additional populations within the historical range of the species, but little is known regarding macroscale habitat requirements that could guide conservation planning. We analyzed local- and network-scale watershed attributes to develop an ecological niche model (ENM) for E. monachus useful for directing conservation actions at sampled and unsampled sites across the Tennessee River Basin. We found E. monachus occurred most often in larger streams with large upstream catchment areas and minimal alteration to forested uplands, but all of these sites were in close proximity to high densities of downstream dams due to populations being restricted to large-stream habitat upstream of reservoirs. The ENM showed the highest probability of E. monachus occurrence among catchment locations with known extant populations; however, additional historical and previously unoccupied catchments showed potential for successful (re)introductions, provided that fine-scale habitats are appropriate. Our framework can be used to identify potential survey and (re)introduction sites for E. monachus as well as other rare riverine fishes and represents a method for identifying areas of high priority for conserving aquatic biodiversity