Trophic Structure and Mercury Bioaccumulation in Walleye and Yellow Perch in the Upper and Lower Red Lake Basins

Author

• Marissa Pribyl

Date of Award

3-2026

Document Type

Thesis

Department

Biology

First Advisor

Andrew Hafs

Abstract

Mercury is a persistent global contaminant that biomagnifies through aquatic food webs, with dietary and environmental factors serving as the primary drivers of accumulation in fishes. Trophic structure and methylmercury dynamics in Walleye (ogaa; Sander vitreus) and Yellow Perch (asaawens; Perca flavescens) were investigated in the Upper and Lower Red Lake basins in Red Lake, Minnesota, during 2024-2025. Diets of Walleye and Yellow Perch were assessed through stomach dissections, and tissue samples from both species were analyzed for total mercury concentrations. Additional analyses included shiners (gigoozens; Notropis spp., Hudsonius spp.) along with a variety of freshwater fish and invertebrates to evaluate mercury concentrations across prey sources. Previous research identified significant basin-specific differences in Walleye mercury concentrations, indicating that lake basin is a critical factor influencing mercury burdens (Orgon et al. 2023). Results from the 2024-2025 study support this conclusion, showing that Walleye, Yellow Perch, and prey items consistently exhibited higher mercury concentrations in Upper Red Lake compared to Lower Red Lake. Emerald Shiners (Notropis atherinoides) and Spottail Shiners (Hudsonius hudsonius) were the most abundant prey species in the Red Lakes and a key component of the Walleye diet. Invertebrates such as Trichoptera, Chironomidae, and Amphipoda were targeted for mercury analysis due to their importance in Yellow Perch diets. These findings highlight the importance of understanding system-specific trophic structures when examining mercury dynamics in large freshwater systems. Such knowledge provides valuable context for interpreting diet-related variation in tissue mercury concentrations and supports the development of fish consumption advisories to better protect the Red Lake community.

Recommended Citation

Pribyl, Marissa, "Trophic Structure and Mercury Bioaccumulation in Walleye and Yellow Perch in the Upper and Lower Red Lake Basins" (2026). Biology Graduate Theses. 17.
https://pines.bemidjistate.edu/thesis-biol/17