Defining economic injury levels for sea lamprey control in the Great Lakes Basin.

摘要

We estimated economic injury levels (EILs) and associated optimal control budgets for sea lamprey Petromyzon marinus for each of the Great Lakes using common assumptions and consistent methods. The lake-specific EILs are defined as equilibrium sea lamprey abundances below which incremental increases in control expenditures do not pay for themselves in terms of 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 adult hosts for fishery harvest, which provides economic value to society. We used a stochastic population model to simulate the sea lamprey life cycle as well as management actions (e.g., treatment of streams with lampricide) over a range of potential control budgets. Prior to running simulations, the model was calibrated for each Great Lake so that resulting forecasts were consistent with recent observed adult (spawning-phase) sea lamprey abundance levels given recent control budgets. Our calculated EILs suggest that sea lamprey abundances lower than those currently observed or those specified by interim damage targets are justifiable and may be obtainable with increases in control budgets (roughly 25% to 55% per lake). This conclusion is robust to a range of plausible assumptions about the economic benefits attributable to host fish.