<p>Scud, <i>Apocorophium lacustre</i>, is a small benthic invertebrate invasive species that poses a substantial risk to the Great Lakes. The species reached the Dresden Island Pool of the Illinois River, where it could reach Lake Michigan via the Chicago Sanitary and Ship Canal (CSSC) through hull fouling, in ballast water, and/or through its own movement. There are potential barriers to invasion within the CSSC that are in place or proposed; however, the effect of these barriers to reduce the spread of scud is not known. Here, we report on three complementary experiments to investigate how water quality, CO₂ barriers, and electric barriers affect the behavior and movement of scud. Results show that scud exposed to water collected from the CSSC have their survival reduced by 20% compared to a control treatment. Our electric barrier and CO₂ experiments show that higher strengths than are practical would be required to effectively impact behavior and reduce movement of scud. These findings indicate that the lack of spread of scud has most likely been a result of water quality in the CSSC. Pollution in the CSSC is driven by Chicago’s sewage and runoff from the highly urbanized and industrialized region. Water quality is improving, however, and our results highlight the need for different management techniques which may be tailored for scud and any other new invaders that are affected by current water quality. The present study demonstrates that current measures may not prevent its spread into the Great Lakes.</p>