Baseline Assessment of Anthropogenic Particles in Ogaa (Sander vitreus) and Asaawe (Perca flavescens) from the Mississippi Headwaters

Anthropogenic particles (APs), including suspected microplastics, are increasingly reported in freshwater ecosystems; however, baseline data remain limited for culturally important freshwater fish in the Mississippi River Headwaters. This study assessed the occurrence and morphology of APs in Ogaa (walleye; Sander vitreus) and Asaawe (yellow perch; Perca flavescens) collected from five northern Minnesota lakes. Gastrointestinal tract, liver, and fillet tissues from 49 fish were processed using a modified hydrogen peroxide digestion protocol and examined by stereomicroscopy. Because polymer confirmation was not conducted, visually identified particles are conservatively reported as anthropogenic particles rather than confirmed microplastics. Forty-one APs were identified across all tissues, with 43% of fish containing at least one particle (0.83±1. particles per fish). Fibers were the predominant morphology, followed by fragments, and walleye exhibited greater AP prevalence and abundance than yellow perch. Although descriptive differences were observed among lakes and tissues, statistical analyses did not detect significant relationships among the variables examined. These findings establish baseline information on AP occurrence in culturally important freshwater fish from the Mississippi River Headwaters and provide a foundation for future investigations incorporating polymer confirmation and expanded spatial and temporal sampling.