Lake Huron Food Web Shifts After Multiple Invasions

Invasive species have had a global impact on aquatic systems. Over one hundred invasive species have invaded the Great Lakes over the last several decades after construction of the Erie Canal and the St. Lawrence Seaway. We are examining the impact of multiple invasion events on food web dynamics of northern Lake Huron using stable isotopes. We are using archived scales and spines from walleye Sander vitreus, brown trout Salmo trutta, and lake trout Salvelinus namaycush to quantify changes in energy source (δ¹³C) and trophic position (δ¹⁵N) dynamics before, during, and after the invasions in Lake Huron. Stable isotope analyses suggest that the invasive Hemimysis anomala and rusty crayfish Orconectes rusticus appear to form the base of the food web distinct from the zebra mussel Dreissena polymorpha in Thunder Bay. The invasive round goby Neogobius melanostomus appear to occupy the next higher trophic position, with strong overlap with several native forage fish (e.g., yellow perch Perca flavescens, emerald shiner Notropis atherinoides, and white sucker Catostomus commersonii) while the intentionally introduced brown trout  occupies the highest trophic position. Thunder Bay is dominated by invasive species occupying all food web compartments.