Gretchen Hansen's adaptive management projects for fisheries management
Experimentation on management relevant scales can disentangle cause and effect in complex systems, and evaluate the response to management actions on the scales relevant for decision making. Adaptive management (AM) is learning by doing, but it is more than just trial and error. AM is structured to ensure that learning occursin spite of variability. Experimentation via AM can be passive, meaning management actions are taken with a specified objective other than learning (e.g., to maximize catch rates of a sport fish species), but set up in such a way so that learning occurs via monitoring and the establishment of reference systems. Active AM means setting up strong contrasts so that learning is maximized, but this approach can be more risky.
Jones, M. L, and G. J. A. Hansen. 2014. Making adaptive management work: lessons from the past and opportunities for the future. Taylor, W.W., Leonard, N., and A. Lynch, eds. Future of Fisheries: Perspectives for the Next Generation of Professionals. American Fisheries Society, Bethesda MD.
Adaptive management of Wisconsin walleye and bass
In response to declining walleye and increasing largemouth bass populations in many northern Wisconsin lakes, managers with the Wisconsin DNR have changed fishing regulations in an attempt to enhance walleye production and increase largemouth bass harvest. In order to maximize the potential for learning about what works in this system, we have established an AM program to evaluate the effectiveness of these regulations in the coming years. This program involves two major components: reference lakes and monitoring. Reference lakes were chosen that had evidence of similar declines in walleye and increases in bass populations, but where experimental regulations would not be implemented. The importance of reference lakes cannot be overstated - reference systems are the only way to truly determine if any observed changes in these systems are due to the management actions, as opposed to environmental conditions. Monitoring is also critical in this way - by monitoring walleye and bass populations in both the experimental and reference lakes, we can evaluate the outcome of management actions on the species are trying to manage.
Hansen, G. J. A., J. W. Gaeta, J. F. Hansen, and S.R. Carpenter. 2015. Learning to manage and managing to learn: sustaining freshwater recreational fisheries in a changing environment. Fisheries 40(2): 56-64.
adaptive management of great lakes sea lamprey
For my master’s thesis, I conducted an adaptive management experiment across the entire Great Lakes basin to evaluate the performance of an alternative method of assessing sea lamprey populations and ranking streams for treatment with lampricides. I worked closely with managers to design an experiment on the scale relevant to management. In each of three years, we assessed the population of larval sea lampreys in every stream scheduled for assessment using both the existing assessment method and the alternative method. To compare the approaches, I quantified the differences in the total number of sea lampreys that would be killed as a result of each assessment method using population estimates generated from the assessments and independent population estimates from mark-recapture studies on a subset of streams. I found that the alternative assessment method outperformed the status quo method, and the international body charged with coordinating sea lamprey management in the Great Lakes subsequently adopted the alternative assessment method in 2008.
Hansen, G. J. A and M. L. Jones. 2008. Evaluating an alternative larval assessment method for Great Lakes sea lampreys: A case study in adaptive management. Canadian Journal of Fisheries and Aquatic Sciences 65: 2471-2484.