Fish begin to die when the concentration of oxygen (DO) in the water falls below?

The concentration of dissolved oxygen (DO) in water is crucial for the survival of aquatic life, including fish. Fish typically require a minimum level of DO to thrive and maintain their metabolic processes. When the concentration of dissolved oxygen falls below 2 parts per million (ppm), fish can experience stress, which can lead to various health issues. At concentrations below 1 ppm, most fish species are unable to survive for extended periods, leading to increased mortality rates.

This level of 1 ppm is critical because, at this concentration, fish are not receiving enough oxygen for essential bodily functions, such as respiration and energy production. While some species may tolerate lower levels momentarily, prolonged exposure to such low oxygen conditions will lead to suffocation and death.

Understanding the significance of these oxygen levels is vital for managing aquatic systems and ensuring healthy ecosystems. Regular monitoring of dissolved oxygen levels is a best practice in aquatic weed control and fishery management to prevent fish die-offs and maintain a balanced aquatic environment.