The presence of Escherichia coli (E. coli) in streams and rivers poses threats to wildlife and human health, particularly in the Great Lakes region, where many water bodies fail to meet total body contact standards. Contamination sources include wildlife feces, agriculture, and poor wastewater management. Dangerous strains like E. coli O157:H7 have caused severe health issues, including hemorrhagic colitis and hemolytic uremic syndrome. While contamination is traditionally linked to water and food, recent studies highlight fish as a potential vector for E. coli transmission.
This study explores fish as bioindicators to identify E. coli contamination sources. During high contamination events (e.g., 300–1000 cfu/100 mL), affected areas are often identified too late, as the contamination flows downstream before analysis is complete. Using fish mucus as a bioindicator could help bridge the gap between sampling, identifying contamination sources, and taking corrective action.
Preliminary data indicate that some river systems harbor E. coli levels exceeding 300 cfu/100 mL, with fish mucus containing 400–1000 cfu/100 mL. Migratory fish species like Brown Trout, which move between Lake Michigan and upstream sites, show lower E. coli levels compared to resident fish species in localized areas, which exhibit higher concentrations. This suggests that riverine systems, similar to beaches, should be monitored more closely and closed during high contamination events to protect public health.