Grzegorz Radtke, Stefan Dobosz
ABSTRACT. Water temperatures in the Radunia River were recorded daily during the 1985-2014 period at the IFI research trout breeding center in Rutki. In comparison to other rivers in Poland, the Radunia is cold. The average annual water temperature over the long-term was 9°C. The highest average monthly temperature was noted in July (17.5°C) and the lowest in January (1.6°C). Some increasing trends for most of the characteristic temperatures were noted. Statistically significant increases were recorded for the summer half-years, and among seasons in the fall. In relation to average monthly temperatures, the highest significant increases occurred in April and November. In winter, a slight but not significant, decrease in temperature was observed. For temperatures in January, a significant increase in the coefficient of variation occurred. In addition, there was an increase in the number of days with temperatures of ł19°C, which is the upper limit of the optimum temperature for rainbow trout. The increase of river temperatures can probably be explained by climate change. These changes can have serious consequences for trout farms that are supplied with surface waters because of the resulting higher incidence of fish diseases, slower growth, and higher mortality.
Keywords: Radunia River, water temperature, rainbow trout, climatic changes
Przyjęto po recenzji 7.07.2015 r.