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To help guide restoration efforts at a large-lake ecosystem (Lac la Biche) in Alberta, Canada, I used Ecopath modeling software to create an energetically plausible model representing the system prior to European settlement. Over the last 200 years, Lac la Biche has shifted from a system dominated by predatory fish (e.g., WalleyesSander vitreusand Northern PikeEsox lucius) to one dominated by forage fish and double-crested cormorantsPhalacrocorax auritus. In 2005, the Fisheries Management Branch of Alberta Environment and Sustainable Resource Development initiated a fisheries restoration program focused on increasing the abundance of Walleyes and average fish size in Lac la Biche; restoration would target a nondescript “historical” ecosystem configuration based on contemporary assumptions of what the system might have looked like. I used Ecopath to organize the main assumptions and information on the historical Lac la Biche ecosystem into an energetically plausible representation for the year 1800. From the modeling process, I learned that most of the assumptions regarding the trends in species biomass between contemporary and historical systems were appropriate guides for model balancing; however, the magnitude of the expected differences between 1800 and the present day were often larger than predicted, especially for infrequently sampled species (e.g., Yellow PerchPerca flavescens, White SuckersCatostomus commersonii, Spottail ShinersNotropis hudsonius, and BurbotLota lota). Testing the validity of single-species assumptions in an ecosystem context is important for improving our understanding of ecosystem structure and function. In a historical context, model creation based on assumptions and available information is important for developing ecosystem baselines that can provide context to and guide future fisheries management. Historical baselines are also important for highlighting ecosystem potential and productive capacity and for counteracting the effects of the shifting baseline syndrome. Received February 13, 2012; accepted August 2, 2013 [ABSTRACT FROM AUTHOR]