The objective of the study was to trace directional reactions of the fry of Siberian sturgeon (Acipenser baeri, Brandt, 1869) to magnetic field of 0.2 and 0.9 mT superimposed on geomagnetic field according to the geomagnetic force lines. In the experimental setup the fish could enter chambers oriented to the N, S, E and W. At the entrance to the chambers the value of magnetic field was increased or only geomagnetic field was active (control sample). The fish reactions were recorded with CCD cameras and analysed. The water temperature in the experimental setup was 17.0 +/- 0.2°C, pH 7.4+/-0.2, and oxygen content 8.2 +/-0.3 mg/dm3. The whole setup was isolated from any external stimuli that could affect the fish behaviour. A total of 400 individuals were subject to two series of experiments. A significant majority (p<0.05) entered the chambers of the experimental setup where the value of the generated magnetic field was higher than the natural background, indicating a directional reaction of the Siberian sturgeon to magnetic field. No difference was observed in the fish reactions to magnetic field of 0.2 mT and 0.9 mT.