From the study analysing behaviour of European catfish (Silurus glanis) was stated that movement of juveniles and adults occurred mostly in the same time intervals. The only statistical differences occurred for nocturnal activity in spring and autumn. Inspring and winter, activity was low and in autumn, maximal movement was recorded during dusk. In summer, the European catfish were active across the whole 24 h even during high-flow conditions. During all other seasons, movement was inversely related toflow rate. Maximal home ranges occurred in summer, being larger for adults. Juveniles and adults were spatially segregated. Only juveniles migrated downstream from the upstream isolated river stretch suggesting a negative impact of lateral obstructionson the fish population structure.