Applying Diet Studies to Assemble Great Lakes Foodwebs

For over forty years, the U.S. Geological Survey Great Lakes Science Center has conducted annual lakewide fisheries assessments and directed research investigations in the Laurentian Great Lakes. Objectives of these studies include monitoring population trends of important fishes, assessing restoration of native fisheries, and evaluating the impacts of invasive species. Ecological linkages are evaluated at multiple life history stages for numerous species, typically through examination of fish diets to glean information on foodweb dynamics. Increasingly, data from diet studies are being applied to models to elucidate and quantify trophic linkages. In this presentation, we discuss five examples from Lake Huron: 1) examination of how diets of larval burbot and deepwater sculpin respond to shifts in zooplankton community structure; 2) recurring examination of adult deepwater sculpin diets reflect temporal changes in benthic macroinvertebrate assemblages; 3) juvenile feeding ecology of a recovering wild lake trout population; 4) assessment of predatory demand on the nearshore fish community by double-crested cormorants; and 5) using crowd-sourced angler-caught fishes to examine how predator diets changed in response to loss of planktivore fish prey. Finally, we synthesize these results to gain insight into recent pervasive Lake Huron foodweb changes.