A comparison of energy pathways to fishes across the Great Lakes

Session: Cross-lake Comparisons: Frameworks for Understanding Ecosystem Change

Anne Scofield, Purdue University, [email protected]
Paris Collingsworth, Purdue University , [email protected]
Tomas Hook, Purdue University, Dept. Forestry and Natural Resources, [email protected]
David Bunnell, USGS Great Lakes Science Center, [email protected]
Timothy Johnson, Ontario MNRF, Glenora Fisheries Station, [email protected]
Aaron Fisk, University of Windsor, [email protected]
Joel Hoffman, US EPA Office of Research and Development, [email protected]
Brian Weidel, U.S. Geological Survey, Great Lakes Science Center, [email protected]

Abstract

Natural stable isotope ratios of nitrogen (?¹⁵N) and carbon (?¹³C) have proven to be valuable tools for identifying basal energy sources for fish production and describing trophic complexity, but cross-lake comparisons of stable isotope data are often limited by challenges associated with standardizing study design and isotopic baselines. Over the past decade, a great number of resources have been invested to generate stable isotope data for the lower food web, prey fishes, and piscivores across all five of the Great Lakes through the bi-national Cooperative Science and Monitoring Initiative (CSMI), providing opportunities for robust cross-lake comparisons. In this study, we investigate differences in nearshore subsidies and trophic transfer efficiencies to fishes across the productivity gradient observed in the Great Lakes, which range from eutrophic (western Lake Erie) to ultra-oligotrophic (e.g., Lake Superior). We examine the basal carbon sources and trophic positions of fish in the offshore regions of the five lakes. Quantifying how trophic structures in lakes differ across a productivity gradient can help elucidate the consequences of human actions such as nutrient management programs, fish stocking, and non-native species introductions.