European catfish (Silurus glanis L.) is a large predatory fish native to an extensive area in Europe. It has been introduced to its western and southern parts, where it is considered an invasive species with a negative impact on native fishes. European catfish is a territorial species exhibiting site fidelity. Cold water in winter usually leads catfish to exhibit notably low activity. Nevertheless, our telemetric study on 19 juvenile individuals of S. glanis provides information on their unexpected high activity and displacement in winter. Our data reveal that these behavioural changes were caused by oxygen deficiency. Our data also indicate that oxygen deficits may induce migrations of this species.