Johnson studies human influences on aquatic ecosystems such as climate, invasive species, reservoir operations, sport fishery harvest regulation, fish stocking and water contaminants.
Johnson’s research blends basic and applied ecology at the intersection of fisheries science, fish biology, and aquatic ecology. His holistic perspective includes all kinds of fishes and interdependent organisms and considers the roles of humans as components of ecosystems, with the overall goal of contributing to the conservation and management of aquatic ecosystems through teaching, research and outreach.
Johnson is affiliated with several professional organizations, including the American Fisheries Society, the Ecological Society of America, and the North American Lake Management Society. He received the AFS Outstanding Mentor Award in 2014.
Johnson studied zoology, earning his B.S. from the University of Wisconsin, Madison, in 1983, his M.S. from Ohio State University in 1986, and his Ph.D. from the University of Wisconsin, Madison, in 1993.