PARENT SESSION
Poster Session 27: Fish Ecology
Thursday, August 11, 5:00 PM - 6:30 PM, Exhibit Hall 220 A-E, Level 2, Palais des congrès de Montréal

100 years of ecological change: Use of stable isotopes to reconstruct the historical food web of Lake Michigan.

Schmidt, Stephanie^*,1, Vander Zanden, M. Jake¹, Fetzer, William¹, ¹ University of Wisconsin - Madison, Madison, WI, USA

ABSTRACT- Waves of aquatic invasive species have been introduced into Lake Michigan in the last century, disrupting food-web dynamics and fish community structure. Once dominated by lake trout (Salvelinus namaycush), ciscoes, and sculpins, the food web is now primarily composed of invasive fishes such as rainbow smelt (Osmerus mordax), alewife (Alosa pseudoharengus), and Pacific salmon. Invasions of exotic species coupled with overexploitation have led to the extirpatin of native deepwater coregonid species. Both the extent and significance of food web disruption is of particular importance concerning restoration goals of fisheries managers and scientists. In this study, we elucidate the historical food web of Lake Michigan using stable isotope (¹³C and ¹⁵N) techniques and museum-archived fish specimens dating back to the early 1900's. Preliminary isotope analysis indicates that the Lake Michigan food web has experienced both a baseline and a food web shift throughout the last century. We discovered an increase in the ¹⁵N signature around the 1970's in almost all fish specimens, most likely due to increased nutrient loading to Lake Michigan around that time period. Furthermore, a shift in both ¹³C and ¹⁵N in the food web was detected with the introduction of non-native species to the system, with the most notable shift after the introduction of alewives. By examining the significance of food web disruption throughout the last century, this retrospective analysis lends insight into the restoration potential of Lake Michigan and benchmarks for such restoration goals.

Key words: food webs, stable isotopes, invasive species