N. baileyi nests under flat rocks, in riffles and shallow pools. Rocks under which nests are constructed are larger in overall dimensions than those used for cover only. Rocks under which either breeding pairs or nests are found average 3.6 cm thick and 25.8 cm in length and width. A nesting site consists of a large, flat rock under which a small pit has been dug into the substrate. ESIS254006 Date 13 MAR 96 devoid of silt, and are presumably prepared by one or both parents.
Aquatic insects are noticeably absent from the undersides of all nest rocks.
Smoky madtoms nest in riffle crests and shallow pools. Male smoky madtoms are found in breeding condition during the months of May, June, and July. Gravid females are found from early May to late July and are identified by their distended abdomens and swollen genital papillae. The enlarged cephalic epaxial muscles and lips, apparent in nuptial males, do not develop in gravid females. A gravid female collected and preserved from Citico Creek had ovaries containing 287 oocytes in three size classes.