We tested the influence of the moon phase and seasonality on the diurnal behaviour of the visually oriented nocturnal predator pikeperch Sander lucioperca (L.) in the channelized Elbe River, located in the Czech Republic. Both the new moon phase and winter season predicted an increase in pikeperch diurnal activity. The distance moved in the longitudinal orientation of the river peaked in spring and autumn, indicating pre-spawning and feeding behaviour.