LAUSR

Abstract Noturus stanauli (Pygmy Madtom) is an endangered ictalurid catfish species endemic to the Clinch and Duck rivers within the Tennessee River system. Little is known regarding the species' habitat preferences due to its rarity, small body size, and the challenging level of collection difficulty in its mainstem riverine environment. In the Clinch River during July, September, and November of 2017, we (1) quantified microhabitat conditions in 1.5-m2 quadrats where we collected Pygmy Madtoms by kick-seining methods and (2) evaluated environmental covariates associated with Pygmy Madtom occupancy and detection using a single-season occupancy-modeling approach. We collected 13 Pygmy Madtoms in July (n = 1) and November (n = 12), with no individuals seen in September. Pygmy Madtoms occupied quadrats with a mean depth of 27 cm, column water velocity of 52 cm/s, water temperature of 12 °C, and substrates dominated by gravel- or pebble-sized particles. Most quadrats with Pygmy Madtom present were located either 1–2 m or 4–5 m away from the nearest bank. Pygmy Madtom occupancy estimates were high (0.498 for the top candidate model) but were not significantly associated with any environmental characteristics. However, the likelihood of Pygmy Madtom detection was significantly related to water temperature (-), with water column velocity (+) and distance to bank (-) playing supportive roles in top candidate models. Our results inform recovery efforts by providing the first quantitative evaluation of Pygmy Madtom microhabitat associations in the Clinch River.