Examining species invasions can provide insight into ecological and evolutionary processes. We examined the distribution of a native crayfish, Procambarus spiculifer, and a non-native crayfish, Orconectes palmeri creolanus, within the lower Flint River Basin, Georgia. Crayfish abundance was estimated by surveys of 26 sites in the Flint River and its tributaries. Within the Flint River, the relative abundance of the two species varied from upstream to downstream. O. palmeri was found almost exclusively at upstream sites, while P. spiculifer was more abundant downstream. O. palmeri collected downstream were larger than those collected at upstream sites, suggesting little recruitment of O. palmeri downstream. Within tributaries, only native crayfish were observed. To examine these trends, we are collecting physical and chemical data throughout the study area. In addition, we are assessing the consumption of the two crayfish species by native and exotic fish predators. These data will provide a possible mechanism for invasion success as well as examples of predator prey relationships that differ due to whether or not the species co-evolved. Understanding the mechanism that allows O. palmeri to be a successful invader in some areas, but not others, may assist in predicting the future invasion potential of this species.