A paucity of observations of winter aggregations have been reported, only in <20% of madtom species, but the behavior is potentially more prevalent. Aggregation behavior may produce benefits such as defense and mate selection, whereas costs include competition and temporal bottlenecks, which can be a risk for imperiled species. We quantified aggregations (measured as an increase in quadrat densities) of Noturus eleutherus (Mountain Madtom) and Noturus stanauli (Pygmy Madtom), and also of the comparative species Nothonotus denoncourti (Golden Darter) and Nothonotus rufilineatum (Redline Darter), leading up to winter during July, September, and November 2017. We observed increasing numbers during each month for all species except during September for the Pygmy Madtom. Understanding grouping behavior of imperiled species and the potential risks of temporal bottlenecks may help inform future conservation planning and management decisions.