Evaluating Upstream Passage and Associated Movement Patterns of Adult Asian Carp at a Gated Dam on the Illinois River

Invasive Bighead Carp (Hypophthalmichthys nobilis) and Silver Carp (H. molitrix), hereafter, Asian Carp (AC), pose a major threat to the Great Lakes ecosystem as they advance toward Lake Michigan via the Illinois River. Starved Rock Lock and Dam (SRLD) is the most downstream gated dam on the Illinois River, therefore presenting the first navigation challenge for upstream migrating AC. Since 2013, less than 1% of acoustically tagged AC have passed upstream through SRLD. In addition, hydroacoustic surveys indicate the abundance of AC significantly declines upstream of SRLD. In 2015, we increased the number of acoustic receivers around SRLD and tagged an additional 119 AC downstream of SRLD. Key findings include 23% of upstream migrating AC that approached SRLD successfully passed through SRLD, AC were more likely to pass upstream through the dam than through the lock chamber, and most passage through the dam occurred during open river conditions when all gates were completely out of the water. Collectively, these results suggest upstream passage of AC through SRLD is more common than previously thought. Our findings will be used to guide AC removal and deterrent efforts around SRLD and at other gated dams along the Illinois and Mississippi Rivers.