V Dyji uhynuly kvůli nedostatku kyslíku až dvě tuny ryb

The recent mass die-off of fish in the Dyje River near Bulhary on Břeclavsko has raised significant concerns among environmental authorities and local communities. According to reports from Czech media outlets, the death toll could reach as high as two tons of fish due to a severe lack of dissolved oxygen in the water. The situation was exacerbated by extreme weather conditions over the past week, which led to dangerously low levels of oxygen in the river. This phenomenon, known as hypoxia, occurs when the concentration of dissolved oxygen in water drops below the level necessary to sustain aquatic life.

The incident unfolded during the night, with oxygen levels in the river dropping sharply. By early morning, the levels had plummeted to nearly zero, causing widespread mortality among fish populations. The drop was particularly dramatic, with readings falling from approximately eight milligrams per liter to almost nothing. This drastic change created a critical threat to the ecosystem, prompting immediate action from multiple agencies including the Fire Rescue Service, the Morava Water Authority, and local fisheries organizations.

Efforts to mitigate the crisis have included the installation of "norná" walls—barriers designed to collect dead fish—and the use of aeration techniques to increase oxygen levels in the water. These measures aim to prevent further loss of aquatic life while allowing for the safe removal of deceased fish. Despite these interventions, the exact number of fish affected remains uncertain, though preliminary estimates suggest several hundred individuals were impacted, with more potentially still lying at the bottom of the river.

The cause of this oxygen depletion is linked to prolonged periods of extremely high temperatures. In southern Moravia, temperatures exceeded 30 degrees Celsius for two weeks, with some days reaching as high as 38 or even 39 degrees Celsius. Such conditions significantly reduce the amount of dissolved oxygen in water bodies, especially in stagnant or slow-moving rivers like the Dyje. This pattern is not new; last summer saw similar incidents, with the Morava Water Authority recording eight instances of fish deaths due to oxygen deficiency, including around 30 tons of fish under the New Mill Reservoir.

Local experts emphasize that while the current situation is alarming, it is part of a recurring cycle influenced by climate trends. The combination of high temperatures and reduced water flow has created ideal conditions for such events. However, the response from authorities has been swift and coordinated, involving collaboration between the Fire Rescue Service, the Moravian Fishermen's Union, the Water Rights Office, and the Morava Water Authority. These groups have implemented emergency protocols to manage the crisis, including temporary relocation of fish to safer areas within the reservoir.

Looking ahead, the focus will remain on monitoring oxygen levels and ensuring that the river environment stabilizes. While the immediate threat appears to be under control, long-term implications for the ecosystem remain a concern. Environmentalists warn that without sustained efforts to address climate-related stressors, such events could become more frequent, posing ongoing challenges for both wildlife and human activities dependent on healthy aquatic ecosystems. As the situation continues to evolve, the collective response highlights the importance of preparedness and cooperation in managing natural disasters.