The blackside dace Phoxinus cumberlandensis is a rare, federally protected cyprinid restricted to small tributaries in the Upper Cumberland River system in southeastern Kentucky and northeastern Tennessee.  The objectives of this study were (1) review blackside dace co-occurrence patterns with nest-building cyprinids and predict the probability of obligatory nest association; (2) determine validity of the prediction by observing spawning activities in the field; and (3) quantify local silt and substrate conditions at and near spawning sites located along a gradient of logging disturbance.  Results indicate that blackside dace constancy was highest for creek chub (Semotilus atromaculatus), while fidelity values were highest with southern redbelly dace (Phoxinus erythrogaster).  In addition, twenty-five spawning events were observed during the study period, 20 of which were seen in sites with no known logging disturbance. All 25 events were associated with creek chub nests, and no evidence of blackside dace spawning independently of these nests was observed.  Also, differences between spawning and non-spawning locations were related to silt depth and embeddedness levels in these areas.  The apparent obligatory relationship that blackside dace have with nest-building cyprinids may assist management agencies in assessing the importance of protecting streams at the fish-community scale.