**The title, authors, and abstract for this completion report are provided below.  For further information on this research, please contact the GLFC via e-mail or via telephone at 734-662-3209 -or- contact the P.I. directly**

Preserved fish as a restoration tool: use of stable isotopes to reconstruct historical Great Lakes food webs

November 2007

Jake Vander Zanden

Center for Limnology,

University of Wisconsin - Madison,

680 N. Park St.

Madison WI 53706 USA

ABSTRACT:

Numerous non-native species have entered the Great Lakes in the last century, and are partially responsible for the decline of native fish species such as the deepwater ciscoes. We used stable isotope analysis (d¹³C, d¹⁵N) of museum archived specimens to evaluate food web change in Lake Michigan and Superior over the last century.  We characterized the food web for each lake over time to examine how introductions of non-native species may have altered the food webs.  The purpose of this project was three-fold:  1) determine the degree to which each lake food web has changed over time, 2) evaluate historical niche partitioning among-deepwater coregonids, and 3) provide an historical context for future fisheries management objectives.  Understanding how the food web structure of the Great Lakes has changed over the last century will lend insight into future management policies, including the reintroduction of extirpated native species. To compare food webs over time, we first developed a statistical tool to quantify food web differences (Appendix I).  We found that the food web structure of Lake Superior did not change over the last century (Appendix II).  Lake Michigan, however, had a food web structure that changed in response to non-native species introductions over time (Appendix III). In addition, we were able to gain significant insight into the historical ecological partitioning of the deepwater coregonines.  Stable isotope analysis revealed ecological niche partitioning between shortjaw and shortnose ciscoes in Lake Superior; two species that were previously argued to be indistinguishable based on morphological characteristics.  We also show that the diverse endemic deepwater coregonines were historically distinct from one another (Appendix IV).  Depth partitioning was evident in the carbon values of the deepwater coregonines.  Isotope analysis revealed distinct ecological differences among all species in four Great Lakes.  Furthermore, those species that were most distinct from one another (i.e. kiyi, bloater, and shortjaw cisco) are species that have persisted to the present.  Ecologically, the deepwater coregonines were unique from one another and the pattern in ecological partitioning was similar across lakes.  This suggests that the deepwater communities of Lakes Superior and Nipigon could potentially serve as sources for reintroduction of deepwater coregonines.  By providing a historical context of trophic niche partitioning of native and non-native species, our findings lend insight into how the Great Lakes fish community has changed over the past century.