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EVALUATING INTEGRATED PEST MANAGEMENT IN THE ST. MARYS RIVER
Michael L. Jones1, Travis O. Brenden1, Brian J. Irwin2
1Quantitative Fisheries Center, Department of Fisheries and Wildlife , 480 Wilson Road, Michigan State University, East Lansing, MI 48824-1222
2USGS Georgia Cooperative Fish and Wildlife Research Unit, Warnell School of Forestry and Natural Resources , University of Georgia, Athens, GA 30602
The St. Marys River (SMR) historically has been and continues to be an important source of parasitic sea lampreys (Petromyzon marinus) for lakes Huron and Michigan. A decision analysis (DA) project was conducted in the early 2000s to help inform management decisions regarding ongoing integrated control of SMR sea lampreys; the results from this project suggested that a program of enhanced trapping and release of sterile males, and moderate levels of annual Bayluscide applications would provide the greatest net economic benefits. In light of persistent challenges in achieving enhanced trapping effectiveness, we conducted an updated DA project to explore integrated management options for the river. An integrated assessment model similar to what was used in the first DA project but which incorporated an additional 10 years of data was used to estimate demographic and control parameters for SMR sea lampreys, including survival and metamorphosis rates, contributions of juvenile sea lampreys to Lake Huron from other sources, contributions of Lake Huron adult sea lampreys to the SMR, Ricker stock-recruitment parameters, and the area-specific mortality caused by applications of Bayluscide. A Bayesian estimation procedure was used to successfully generate a stable joint posterior probability distribution for all estimated parameters, thereby allowing characterization of the uncertainty of each estimated parameter or derived variable. We used a model similar in structure to the integrated assessment model to forecast SMR and Lake Huron sea lamprey abundances conditional on a range of potential management scenarios. To account for demographic and control uncertainty, simulations were repeated 1000 times. For each iteration, an independent random sample of parameters and initial conditions was drawn from the estimated joint posterior probability distribution. We compared a reference strategy of no control to scenarios with increasing areas treated annually with Bayluscide (100-400 ha) and to a scenario with 200 ha treated and the annual release of 25,000 sterile male sea lampreys. We repeated these scenarios for two models, one in which we assumed average trapping effectiveness in the SMR was 40%, based on historical evidence, and a second in which we assumed trapping effectiveness was 8%, based on recent acoustic telemetry findings. The simulation results suggested that with annual Bayluscide treatment of 400 ha, the adult sea lamprey population returning to the SMR was largely derived from juvenile production from other sources as SMR juvenile production was reduced by over 90% relative to the “no-control” treatment strategy. Releases of sterile males had only a small effect on juvenile production in the scenarios we examined, and in fact resulted in slight increases in juvenile production under the 8% trapping effectiveness scenario. Our stock-recruitment analysis suggested that recent sea lamprey spawner abundance was near (40% model) or somewhat above (8% model) the abundance expected to result in peak recruitment. The implication is that adult control tactics (trapping and sterile male releases) will only be effective in the SMR if overall adult abundance can be reduced to levels substantially below that associated with peak recruitment.