Quantifying Heterogeneous Impacts of Invasive Zebra Mussels on Walleye Habitat, Food Webs, and Mercury Concentrations

The ultimate goal of this work is to understand the multiple pathways through which invasive zebra mussels impact walleye, and to identify factors that make lakes more or less vulnerable to these impacts.

Any zebra mussel-induced changes in walleye habitats, populations, and mercury contamination of walleye have important implications for harvest, stocking, and consumption in lakes of the upper Mississippi river basin. Changes in walleye habitat and food webs can serve as early indicators of aquatic invasive species impacts on the capacity of a lake to support abundant walleye populations. Quantifying zebra mussel effects on walleye will inform proactive management and allow for realistic goal setting of harvest, stocking practices, and data-driven communication following species invasions before a crisis develops. Understanding sources of mercury in walleye and how they are influenced by zebra mussels is critical for fish consumption advisories in lakes. In all cases, identifying factors that influence the resilience of lakes to these impacts can inform prevention efforts to focus on the most vulnerable systems, and quantify lake-specific impacts to avoid one size fits all recommendations. The results of this project will supplement ongoing work and enable sampling of large number of lakes spanning a gradient of biotic and abiotic conditions, which will enable identification of factors conferring resilience of walleye populations to the impacts of zebra mussels.


1. Assess the sensitivity of walleye habitat in lakes in the upper Midwest to increases in water clarity associated with zebra mussel invasion;
2. Quantify the relative reliance of age-0 and adult walleye on littoral vs pelagic resources in invaded and uninvaded lakes.
3. Identify drivers (invasion status, trophic position, growth, shifts in foraging regions, and mercury production rates) may be causing shifts in mercury exposure for walleye following zebra mussel
invasion in lakes.

Project manager: Gretchen Hansen

Funded by: USGS

Project start date: 2020

Estimated project end date: 2023