Barriers in the Great Lakes represent an effective form of control for the invasive sea lamprey (Petromyzon marinus) by blocking large extents of river habitat and subsequently eliminating the need for the lampricide treatments in these upstream areas. With increasing pressure for barrier removals, the availability of suitable sea lamprey habitat above these barriers and the expected population response to dam removals represent key uncertainties in decision-making. The development and evaluation of models to predict larval habitat quantities using readily-available, reach-scale landscape predictors improved our understanding of common influences on stream habitat, but failed to reliably predict habitat proportions upstream of barriers in the Lake Michigan drainage basin. Subsequent simulation-based modeling of the Lake Michigan sea lamprey population revealed a disproportionate, exponential response to increasing habitat availability, driven in part by decreasing overall lampricide treatment frequencies under a fixed control budget. The same modeling approach was used to generate sea lamprey population predictions associated with projected removal of Grand River's Sixth Street Dam under a suite of alternative management actions and biological assumptions. Based on all simulation results, barrier removals appear to necessitate a substantial increase in annual lampricide control costs to prevent disproportionate increases in sea lamprey abundance across the Lake Michigan basin.
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