The spatial ecology of reproductive effort and juvenile dispersal is poorly understood for most nongame stream fishes. We used genetic marker data to investigate these ecological attributes in the 2005 cohort of Roanoke logperch (Percina rex) in the upper Roanoke River. Ninety-­‐four individuals from this particularly large year-­‐class, as well 37 potential parents, were captured along a 55-­‐km reach of the Roanoke River and its two forks (15 spatial sites). Microsatellite genotype data were used to estimate relatedness between individuals and reconstruct full-­‐sib families. We found that juvenile logperch were no more closely related within than among sampling sites, and no relationship between spatial distance and relatedness was detected. Family reconstruction indicated the presence of many small families: 60 full-­‐sib families were inferred, each containing from one to three individuals. Most families were captured across multiple sampling sites, indicating dispersal of juveniles, dispersal of spawners between clutches, or both. Family members were widely dispersed, separated by an average of 13 km and up to 45 km. The number of breeders that produced the sample was estimated to be in the hundreds, and the total Ne of the 2005 cohort was estimated to be in the thousands. Extensive dispersion of spawning effort and/or juveniles appears to promote genetic panmixia over large distances in this population, and may enhance fitness and dampen population fluctuations in variable riverine environments.