Ontogeny of the diel activity patterns in relation to downstream dispersal in riverine cyprinid fishes

Young‐of‐the‐year (YOY) riverine fish use the facility of water currents to disperse downstream from their spawning sites. We combined data on the diel changes in YOY fish activity and their distribution in the river to investigate a relation between the onset of their downstream movement and ontogeny of their diel activity. Plexi‐glass traps and electrofishing were used to investigate the activity and distribution of YOY fish. Fish species such as Leuciscus leuciscus, Leuciscus cephalus, Chondrostoma nasus, Barbus barbus and Rutilus rutilus dominated our samples from two separate study sites in the River Morava. Results are discussed in context of ontogeny of phototrophic and rheotrophic behaviour, seasonality, diel periodicity and stage‐dependence of the downstream movement and also in relation to environmental (river discharge, water temperature) variability.