Apocorophium lacustre abundance (per sample on the log-scale, calculated with natural log of abundance + 1) at rock bag sites within all pools (where detected) across the Illinois River portion of the Illinois Waterway as a function of distance downstream in river kilometers (higher values are closer to the next downstream dam). Note that the Alton Pool is an exception because it is undammed; the downstream end of the Alton Pool is the confluence of the Illinois and Mississippi rivers whereas the downstream ends of other pools are dammed. Pool specific trendlines represent linear lines of best fit based on associated data points.