French rivers are subject to winter floods. The northern pike (Esox lucius) needs these, as it performs lateral migrations for breeding. On the contrary, the allochthonous European catfish (Silurus glanis) is known to be less active in winter. However, very few studies have focused on the behaviour of these two predatory fishes during winter floods. Thus, we propose to characterize their respective responses to high waters, using a radio telemetry approach: thirty northern pikes and seven European catfish were tagged with radio transmitters in the Aisne River (northern France) and monitored between October 2020 and May 2021. As a result, some northern pikes and at least one catfish were recorded in the major bed, in various habitats, during two major floods. A “preferential zone” was identified for the northern pike and defined from the pre-flood positions; three types of behaviour were identified: “sedentary” pikes never left these zones, “returned” pikes left during floods but returned when the water level dropped, and “departed” pikes did not come back at all. Individuals from the departed group were significantly larger than those from the other two groups (5% threshold), and those in the sedentary group significantly smaller (10% threshold), suggesting a greater exploration capacity in experienced northern pikes. Meanwhile, the supposed winter quiescence of the European catfish can be questioned, as our observations highlight an adaptability to various conditions. These results also underline the importance of taking the major bed into account in riverine management policies.