Exploring Impediments to Saginaw Bay Yellow Perch: Empirical Observations & Individual-Based Model Implications

Yellow perch are ecologically and economically important components of the Saginaw Bay fish community.  Despite recent (since 2003) increased production of age-0 yellow perch, adult abundance has continued to decline (1970-2008) and current spawning stock biomass is near an historic low.  Coincident with yellow perch declines, various stressors have emerged to influence the Saginaw Bay ecosystem.  Invasions by non-native species such as dreissenid mussels, round gobies, and Bythotrephes sp. have impacted physical and chemical characteristics and altered the prey base of Saginaw Bay.  Simultaneously, the crash of the Lake Huron alewife population has led to high larval percid survival, and subsequent increased walleye recruitment.  In contrast, yellow perch recruitment has remained low, with the burgeoning walleye population likely leading to increased predation on yellow perch during the critical first year of life.  Abundance of other prey that may have historically buffered predation pressure remains low.  Poor survival is exacerbated by the current slow growth of age-0 yellow perch, which may be a response to density-dependent processes and changes in composition of perch diets.  To explore these processes, we link a biophysical model to an individual-based model to simulate past and potential future dynamics of yellow perch in Saginaw Bay under various scenarios, including changes in climate, nutrient-induced prey availability, and fish community composition.