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EVALUATING TRADE-OFFS FOR SEA LAMPREY MANAGEMENT USING AN OPERATING MODEL OF THE CONTROL PROGRAM
Michael Jones1, Alex Jensen1, Heather Dawson2, and Dana Infante3
1Quantitative Fisheries Center, Department of Fisheries and Wildlife, 480 Wilson Road, Room 13, Michigan State University, East Lansing MI 48824
2Biology Department, 264 Murchie Science Building, 303 E. Kearsley Street, University of Michigan-Flint, Flint, MI 48502
3Center for Systems Integration and Sustainability, Department of Fisheries and Wildlife, 480 Wilson Road, Room 13, Michigan State University, East Lansing MI 48824
Sea lamprey management is facing pressures to balance the benefits of lamprey control against other, potentially conflicting ecosystem objectives, including provision of migratory corridors for valued native fish populations and reductions in the use of chemical pesticides. We used a Management Strategy Evaluation simulation model to explore (1) the potential for using trapping strategies as a complement to lampricide control that would allow reduced reliance on the latter, and (2) the consequences of barrier removals for basin-scale sea lamprey production. We found that trapping strategies that targeted streams with relatively low spawner densities were most effective, relative to targeting other stream types, but will require low costs (<$5,000 per trap) and high capture rates (> 50%) to be a cost effective substitute for lamprey control. Simulations specific to Lake Michigan revealed that targeting large, relatively productive rivers, with low spawner densities, resulted in the best performance outcomes; these rivers are very expensive to treat with lampricide, and if trapping strategies reduce the frequency with which these streams are treated, the benefits are substantial. Our simulations of barrier removal scenarios revealed a large, disproportionate response of lake-wide sea lamprey abundance to relatively modest increases in available habitat for spawning and larval rearing. For example a 20% increase in habitat resulting from one or several barrier removals resulted in a 161-800% increases in lake-wide parasitic sea lamprey abundance. Application of the model to a case study – the Sixth Street Dam on the Grand River in Michigan – suggested that removal of this dam would lead to increases in Lake Michigan sea lamprey abundance ranging from 52-269% if no additional funds were allocated to sea lamprey control for Lake Michigan. To maintain lake-wide abundance at current levels after removal of the Sixth Street Dam, we estimated an increase in the Lake Michigan control budget of between $200,000 and $360,000 per year would be required; the range depended on assumptions about the extent of new habitat utilization by sea lampreys colonizing areas upstream of the existing barrier.