Using long term data to improve sea lamprey control efforts in the Saint Mary's River, Michigan

The St. Marys River contributes significantly to the lake wide population of sea lampreys (Petromyzon marinus) in Lake Huron and upper Lake Michigan and presents a unique challenge to sea lamprey control due to its size. A portion of the sea lamprey control program in the river focuses on controlling the larval life stage through the application of granular Bayluscide. The ultimate goal of these treatments is to reduce sea lamprey mortality on lake trout. Decisions about which plot to treat are currently based on only the most recent year’s data, although 16 years of plot-level data are available. The St. Marys River has been divided into 71 plots. Sampling and treatments are conducted on a plot by plot basis, but resources are not available to sample or treat all plots each year. We used several modeling approaches that incorporated these historical data to describe larval sea lamprey dynamics and abundance in response to treatment efforts. Larval abundance at the plot level was strongly influenced by the length of time since the last treatment and habitat characteristics. This work will help to refine sampling techniques and provide more accurate assessments of larval sea lamprey abundance leading to more effective control.