The red shiner (Cyprinella lutrensis) has been widely introduced across 11 states outside its native range, presumably through bait-bucket and aquarium releases. Its native range includes Great Plain and Central Lowland tributaries of the Mississippi River and western Coastal Plain drainages of the Rio Grande River. This species thrives under harsh conditions (e.g., low flow, high turbidity, poor water quality) and aggressively colonizes severely degraded habitats. Introduced populations spread rapidly, often displacing native Cyprinids. Red shiners readily hybridize with congeners, sometimes causing widespread displacement of native species. Hybridization is a significant threat to Southeastern Cyprinella, as red shiner hybrids have been reported for nine native taxa. NERL scientists, in collaboration with researchers at U.S. Geological Survey (USGS), The University of Georgia, and Duquesne University, conducted three related studies on the dynamics of red shiner invasion and hybridization with native blacktail shiners, C. venusta stigmatura, in the upper Coosa River System (UCRS). The overall goals of these studies were to identify environmental drivers of red shiner invasion and to determine genetic and environmental factors promoting hybridization.