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Determining the population demographics of threatened or endangered species can be difficult if the methods that are used must be minimally invasive. However, knowing the population status of species that are of conservation interest must be understood for successful management. We used underwater observations (i.e., snorkeling) to determine population estimates for Spotfin Chub Erimonax monachus in the Cheoah River in North Carolina, a species that is listed as threatened at both state (North Carolina) and federal levels. Seven sites were randomly selected between the Santeetlah Dam and the confluence with the Little Tennessee River. Each site was surveyed by three snorkelers who completed multipass snorkeling from July 17 to 25, 2019. The population estimates were generated with an N-mixture model and incorporated site-specific habitat. Four hundred and sixty-six observations of Spotfin Chub were recorded across all of the sites and passes. The simple model without covariates of abundance estimated a total population size of 12,139 (95% credible interval [CRI] = 9,821-15,453). Incorporating site-specific percentage of bedrock improved model fit and indicated that the percentage of bedrock was positively related to site-specific abundance. The total population size as estimated with the covariate model was 13,905 (95% CRI = 11,620-22,181). Our results yielded new insight into the status of a threatened species while confirming previous knowledge about its microhabitat use. Locally, the results of this work suggest that Spotfin Chub are well established in the Cheoah River and maintain a substrate affinity to bedrock. Broadly, the field methods that were used here are logistically feasible, cost efficient, and minimally stressful for the fish. We suggest that this methodology be considered when total and site-specific population estimates are needed to manage species of concern. Additionally, more detailed site-specific habitat can improve model estimates by explaining site-specific variability in abundance, resulting in more precise total population estimates.

Understanding the population dynamics of rare and endangered species can be difficult, particularly when a species has a narrow geographic range. The Spotfin Chub Erimonax monachus is both federally and state (North Carolina) listed as threated and is endemic to the Tennessee River basin in the southeastern United States. The Spotfin Chub was once found throughout the Tennessee River basin, but its range has been reduced to four river systems. The Little Tennessee River contains the only known population of Spotfin Chubs in North Carolina. However, current efforts are ongoing to restore populations in the Cheoah River (Little Tennessee River basin). The goal of this study was to evaluate the status of Spotfin Chubs in the Little Tennessee River and to determine potential information gaps to guide future studies. Specifically, we evaluated temporal trends of the Spotfin Chub in the river using a state–space model that incorporated multiple data sources. We additionally evaluated current habitat availability to better understand how habitat could be driving site‐level variation in abundance. We found an overall increasing trend in Spotfin Chub abundance over time, but there was substantial variation across years. By linking abundance trends to current habitat availability, we found that sites with generally more bedrock also had the highest estimated abundance. The Spotfin Chub population appears to be stable; however, determining more specific population demographics (e.g., recruitment and mortality) would improve our understanding of this threatened species.

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