Lakescape connectivity: Mobile fish consumers link Lake Michigan coastal wetland and nearshore food webs

In large lake ecosystems, fish movement between coastal littoral habitats such as wetlands and the adjacent open-water nearshore represents an understudied but potentially important linkage supporting energy flow and fisheries production. We hypothesized that yellow perch (Perca flavescens), an ecologically and economically important sport fish in the Laurentian Great Lakes, transport energy from highly productive wetlands to nearshore food webs, but that their role changes with ontogenetic shifts in diet and habitat use. We also predicted that the relative strength of such fish-mediated habitat linkages would vary depending on physical connectivity across habitats. We collected perch and potential prey resources from seven paired coastal wetland-nearshore sites across three regions of Lake Michigan and quantified resource and habitat use with Bayesian stable isotope mixing models and otolith microchemistry. We found that juvenile perch collected in nearshore habitats showed high use of wetland resources, and that diets of wetland-collected juveniles typically contained a smaller proportion of nearshore resources than did more mobile adults from the same wetland. The least hydrologically connected sites had lower cross-habitat resource use (e.g., wetland-collected perch consumed fewer nearshore resources and vice versa) compared with sites with greater levels of hydrological connectivity. Otolith microchemistry confirmed the linkages revealed by stable isotopes, suggesting that a dual approach can increase understanding of habitat linkages in large lakes. Quantifying the importance of multiple lentic habitats (i.e., "lakescape connectivity ") for fisheries production is critical for developing comprehensive large lake food web models and providing managers with information to prioritize locations for conservation and restoration.