In 2011, USGS researchers began studying Lake Erie's fish and seasonal hypoxia across a multi-year project. 15 years later, the findings showed fish crowding areas near 2–3 mg/L oxygen, revealing an unexpected shift at the edges of low-oxygen zones

Lake Erie’s seasonal hypoxia is changing where fish gather. For years, scientists watched oxygen levels fall and fish move around the lake. Then came a surprising pattern. Fish were not simply escaping low-oxygen water. Many crowded near the edges of these “dead zones,” where oxygen hovered around 2–3 mg/L. The finding offers a new look at Lake Erie’s underwater ecosystem.