A standardized sampling dataset collected from 1991-2007 on the Satilla River, Georgia, was used to document changes in bluegill (Lepomis macrochirus), largemouth bass (Micropterus salmoides), and redbreast sunfish (L. auritus) populations after the introduction of flathead catfish (Pylodictis olivaris). Repeated measures ANOVA was conducted incorporating a control area, where flathead catfish abundance is extremely low, and a flathead area, where flathead catfish have become well established, for both before (1991-1995) and after (1996-2007) flathead invasion. The analyses revealed that the mean log-transformed electrofishing catch per hour (log10-CPH) of redbreast sunfish and largemouth bass decreased significantly in the flathead area but not in the control area following flathead introduction. Mean log10-CPH of largemouth bass between 150-299 mm TL increased in the control area but remained unchanged in the flathead area. No other significant differences in trends were found for bluegill or other size groups of these sport fishes between areas following flathead introduction (P >0.10). Our analyses suggest that establishment of flathead catfish in the Satilla River may have contributed to observed declines in some sportfish populations in the Satilla River. Long-term data sets like the standardized sampling events examined can prove to be valuable management tools for fisheries biologists when assessing the potential effects of an introduced species on a system.