Movement and Activity Patterns of Non-Native Wels Catfish (Silurus glanis Linnaeus, 1758) at the Confluence of a Large River and Its Colder Tributary

The establishment and proliferation of non-native fish species can have a range effects within the local ecosystem, including alteration food webs, nutrient cycling, pathogen dynamics predation, sometimes also resulting in changed behavior distribution native species. Knowledge about movements activity patterns is important to understand animals their new environment. Wels catfish (Silurus glanis Linnaeus, 1758) considered an invasive many places Western Europe, regional control programs are place. Here, using radiotelemetry, we study at invasion front Po River (Italy); namely, confluence between main river, where abundant, colder tributary, Dora Baltea River, it absent. In addition, investigate potential spatiotemporal overlap endangered marble trout (Salmo marmoratus Cuvier, 1829) area. A total nine eight were tagged. showed very high degree residency area close mouth tributary. Despite this, only one entered lower reaches tributary did so occasionally during August. No moved further upstream It likely that temperatures combination with more challenging hydrodynamic conditions made unattractive catfish. active all times day but substantially evenings nights. Some, not all, tagged areas stem large proportion occasional or longer visits several individuals becoming resident, without apparent mortality, home range. suggests removal efforts may do well initially focus on habitats under conservation concern.