**The title, authors, and abstract for this completion report are provided below. For a copy of the completion report, please contact the GLFC via e-mail or via telephone at 734-662-3209**
Defining Targets for Sea Lamprey Control in the Great Lakes:
Economic Injury Levels and Fish Community Goal-based Targets
1Quantitative Fisheries Center, 153 Giltner Hall, Department of Fisheries and Wildlife, Michigan State University, East Lansing, MI 48824
213 Natural Resources Building, Department of Fisheries and Wildlife, Michigan State University, East Lansing, MI 48824
East Lansing, MI 48824
We estimated economic injury levels (EILs) and the associated treatment budgets for sea lamprey (Petromyzon marinus) control for each of the Great Lakes using common assumptions and methods. EILs are sea lamprey abundances below which incremental increases in control expenditures do not pay for themselves in terms of fishery benefits (in the form of increased harvest of desired host species). We assume that sea lamprey control efforts result in an increase in the availability of additional adult hosts for fishery harvest, which provides additional economic value to society. For each of the Great Lakes separately, we used a stochastic population model to simulate the entire sea lamprey life cycle as well as management actions that can affect multiple generations (e.g., treatment of streams with lampricide) over a range of potential control budgets. Model simulations relied on input data (e.g., stream-specific measures of larval habitat and growth), which were provided by the Great Lakes Fishery Commission (GLFC) and by sea lamprey biologists and managers at a project workshop and through later correspondence. In response to recommendations from these interactions with sea lamprey control agents, various modifications to the simulation model (inclusion of drainage-area information, incorporation of a non-linear larval growth model, variable treatment effectiveness, inclusion of treatable lentic habitats) were made during this project. Prior to running simulations, the model was calibrated for each Great Lake so that it replicated recent observed spawning-phase sea lamprey abundance given recent control budgets. We also compared our calculated EILs with current GLFC/Lake Committee accepted interim damage targets for spawning-phase sea lamprey abundance. Current damage targets suggest that a substantial reduction of sea lampreys across the Great Lakes is desired. Our EILs suggest that even lower average levels of sea lamprey abundance are justifiable, and may be obtainable, with a sufficient sustained increase in expenditures on control. This conclusion relies on the assumptions that lentic area treatments could successfully reduce some previously untreated sources of sea lampreys and remaining “untreatable” areas would produce few sea lampreys.