Long‐Term Population Dynamics and Habitat Association of the Federally Threatened Spotfin Chub in the Little Tennessee River

Abstract

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.

Incorporation of feeding functional group information informs explanatory patterns of long-term population changes in fish assemblages

“…Zooplankton were sampled at a fixed site using vertical tows of a 153-μm mesh net. Long-term trends in the fish assemblage were described using a multi-species exponential population growth model in a state space framework ( Kéry & Schaub, 2012 ; Doll et al, 2020 ). This modeling approach separates the biological process model from the observation process model to separate variation from the two sources.…”

“…Temporal trends of all species were evaluated using a state space modeling approach ( Kéry & Schaub, 2012 ; Doll et al, 2020 ). State space models have been widely used in fisheries and ecology to better understand long-term changes in population structure.…”

“…Specific applications include stock assessments ( Nielsen & Berg, 2014 ; Aeberhard, Flemming & Nielsen, 2018 ), animal movement and migration ( Jonsen, Myers & James, 2006 ; Patterson et al, 2008 ), identify metapopulation structure ( Ward et al, 2010 ), and understanding foraging tactics of gray seals Halichoerus grypus ( Breed et al, 2009 ). The base model is similar to the model used in Doll et al (2020) . The species specific biological process model (i.e., population dynamics model) was assumed to follow the exponential growth model: where N t +1 represents the population size during time t +1, N t represents the population size at time t and represents the population growth rate at time t and t ranges from 1 to the total number of years where data were collected.…”