Disentangling The Effects Of Multiple Ecosystem Changes On Fish Population And Community Dynamics

Abstract

North temperate lakes are undergoing diverse physical, chemical, and biological changes, including warming water temperatures, shifts in lake trophic states, and introductions of non-native species. These ecosystem perturbations rarely occur in isolation, making it difficult to evaluate the impacts of concurrent perturbations on population and community dynamics. Here, I use Oneida Lake, New York, USA, to study interactions among multiple ecological changes and their combined effects on age-0 and juvenile yellow perch (Perca flavescens). These ecological changes included diversification of the predator and prey communities, shifts in lake trophic state from eutrophic to mesotrophic, and an expansion of littoral habitats. Multiple long-term limnological and fisheries datasets were integrated with short-term diet studies of age-0 yellow perch and their predators from nearshore and offshore habitats to develop a multi-habitat understanding of lake-wide responses to ecosystem perturbations. Walleye (Sander vitreus) were still the most important predator on age-0 and juvenile yellow perch, though the importance of alternative predators, such as white perch (Morone americana), smallmouth bass (Micropterus dolomieu), and largemouth bass (Micropterus salmoides), was also high and has likely increased. Consumption of age-0 yellow perch was dominated by walleye and white perch in offshore habitats during early summer, but transitioned to walleye, smallmouth bass, and largemouth bass in nearshore habitats during the fall and second year of life. As ecological conditions within the lake changed, age-0 yellow perch population dynamics became increasingly driven by littoral habitats and the population-level reliance on benthic energy pathways increased from 10-20% in the 1960s to 30-70% in the 2000s. These results illustrate the importance of both nearshore and offshore habitats to age-0 and juvenile yellow perch population dynamics and highlight the complexity of population- and community-level responses to ecosystem perturbations.