Clean Water Act §316(b) Compliance on Lake Michigan, Quantifying Adverse Environmental Impact

Clean Water Act §316(b) directs certain facilities that withdraw waters from Lake Michigan to minimize adverse environmental impact (AEI) resulting from cooling water intake structures.  AEI is quantified by extrapolating fish mortality from impingement and entrainment samples.  Based on evaluations of historical impingement data from facilities on Lake Michigan spanning up to 50 years the abundance, species, and life stages of fish sampled shifts temporally and correlates with life-cycle behaviors.   Analyses of these data revealed that young-of-the-year (YOY) yellow perch (Perca flavescens) are one of the more commonly impinged species relative to other species during certain sample periods.  Over the past 20 years, it is generally viewed that the Lake Michigan yellow perch fishery has improved.  As an example of a potential evaluation for AEI, this study will compare the temporal estimates of impinged fishes to government generated data describing fish abundance in Lake Michigan to examine the wider impact that YOY yellow perch and other fishes’ impingement mortality may be having on the ecology of Lake Michigan and its fisheries.  This investigation will help improve quantification of AEI, which will be a crucial step in helping facilities understand how to adequately protect fish based on species’ specific impingement thresholds.