US Long-Term Ecological Research Network
Making the weedline work for your lake: when life gives you invasive weeds, make habitat
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Throughout Wisconsin, lakes heavily infested with Eurasian water milfoil often contain stunted populations of bluegill and largemouth bass. We tend to manage these lakes by cutting the watery weeds without appreciating the connection between the plants and the fish. Could we achieve more by viewing and managing these plant and animal communities together? The Department of Natural Resources, the University of Wisconsin’s Center for Limnology, and the Dane County Public Works Lakes Management Program took on a joint project to find out. We spent three years investigating if the way aquatic plants are harvested can grow bigger fish more quickly. Many nutrient-rich lakes in Wisconsin are dominated by Eurasian water milfoil, an invasive aquatic plant that can grow from the surface to as deep as 16 feet, forming dense beds of leafy canopies over strong, spaghetti-like stems. Milfoil most often reproduces by breaking into fragments, which are then spread around by wind and boats within a lake. The plant is commonly moved from lake to lake on boat trailers and in live wells. Though it is often viewed as an invasive pest, milfoil infestations aren’t always bad. In lakes where there is little native vegetation, Eurasian milfoil can provide refuge and spawning habitat for fish and invertebrates. Even in heavily infested lakes, milfoil typically lasts only about 20 years, eventually dying down as weevils and other factors reduce its spread. Nevertheless, when swimmers get tangled and boats get mired in the dense weeds, milfoil becomes a problem.