Control of invasive crayfish populations has been successful in a small number of ponds and lakes but few studies have been conducted in flowing stream or river systems. Procambarus clarkii (red swamp crayfish) is a species of great concern in the Laurentian Great Lakes area due to the recent discovery of established populations in inland and Great Lakes-connected waters. A high-density population is established in the North Shore Channel of the Chicago Area Waterway System (CAWS) which connects Lake Michigan to the Mississippi River Basin. We have implemented intensive trapping and removal of P. clarkii to reduce population size in this system during seven consecutive summers (2018-2024) using baited traps. To determine the effects of trapping on population size we compared catch per unit effort (CPUE) in removal reaches to a control reach and used linear regression of the ratio of CPUEs to determine if our removal efforts were significantly affecting population size. The ratio of CPUE did increase significantly in 2018 (two trap reaches; p<<0.05 for both), 2020 (two trap reaches; p<<0.005 for both), 2021 (four trap reaches; p<<0.005 for all), 2022 (four trap reaches; p=0.01 for one reach), 2023 (four trap reaches; p<<0.05 for two reaches), and 2024 (four trap reaches; p<<0.05 for all). For these years, our trapping efforts led to a reduction in P. clarkii CPUE in removal reaches relative to the control reach. Our study demonstrates that although eradication of an established population of invasive crayfish such as P. clarkii is unlikely in a river system, control efforts can reduce population size and may reduce chance of further spread and ecosystem impacts.