Predicting and addressing impacts of human-induced rapid environmental change has become a pressing issue for ecosystems worldwide. Lake Erie is experiencing substantial ecosystem change. Due to the combined effects of invasive species, climate change, and intensive agriculture in its watersheds, Lake Erie now has an altered species composition, is warmer, has a longer growing season, and receives more bioavailable nonpoint source phosphorus relative to the past. These changes underlie Lake Erie’s recent re-eutrophication and we suspect that they are altering the quality of habitat available for ecologically- and economically-important fishes, such as walleye (Sander vitreus) , as well as potential predators and prey of walleye. However, Lake Erie comprises three geomorphologically distinct basins (west, central, east), with depth increasing and temperature and productivity decreasing from west to east. As a result, ecosystem change may differentially impact each lake basin’s habitat quality. To explore these potential basin-specific impacts, we used archived data and biophysical modeling to quantify relationships between observed life stage-specific walleye abundance and habitat features that are known to directly or indirectly affect habitat use, growth, or survival.
Walleye recruitment dynamics have been shifting over time, with westerly stocks underperforming relative to easterly ones. The overall, lakewide trend has been negative. Considering changes to the thermal, foraging, and predation components of habitat quality for larvae and adults suggest that the quantity of high-quality habitat for larvae and adults, as well as the walleye’s resultant production potential, has decreased in the west but increased to the east. However, gains in the east have not fully compensated for losses in the west. In general, our results suggest that projecting impacts of ecosystem change on populations of interest may be complicated by heterogeneity in habitat characteristics across the population or species’ range. Projecting the overall impact will require an understanding of the full life history of the species, including its habitat needs at all life stages, its capacity for dispersal, and its interactions with other species that may be impacted by the same ecosystem change.