European Flounder Discovered Living Entirely in Freshwater in Finland’s Lake Pulmanki

A new study published in Evolution reveals that European flounder, a flatfish typically associated with marine and brackish environments, can complete its entire life cycle in freshwater. Researchers found that most flounders sampled in Lake Pulmanki, located in northern Finland, had spent their whole lives in the lake, providing the first evidence of the species living entirely in freshwater. The discovery challenges previous assumptions about the species’ habitat requirements and highlights its remarkable adaptability. Lake Pulmanki, a remote freshwater body, serves as a natural laboratory for understanding how marine fish can colonize and thrive in new environments. This finding has implications for evolutionary biology and conservation, as it suggests that European flounder may be more resilient to environmental changes than previously thought. The study underscores the importance of long-term ecological monitoring in northern ecosystems, where climate change is rapidly altering habitats. As freshwater systems face increasing pressures, understanding species like the European flounder could inform future management strategies.