In 2026, cases of mass fish mortality were recorded in Kazakhstan, Uzbekistan, China and Russia. The causes vary: shallowing and freezing of water bodies, oxygen deficiency, heat and algal blooms, municipal and industrial wastewater. Using individual episodes as examples, the article shows why it is impossible to draw conclusions about the cause of pollution from the appearance of dead fish without laboratory analysis. Particular attention is paid to the growing pressure on freshwater and the risks to water bodies amid climate change and rising water consumption.