Individual movements, home ranges and habitat use by native rheophilic cyprinids and non-native catfish in a large regulated river

The mobility patterns of two native species, barbel, Barbus barbus (L.) and chub, Squalius cephalus (L.), and of one non-native fish species, the catfish Silurus glanis (L.), were assessed on a 35.5-km reach of the Upper Rhone River, a strong flowing river with notable thermal regime alterations. An active acoustic tracking technique adapted to large rivers allowed (1) the identification of longitudinal home ranges, movements and preferred habitat at large scale, and (2) the analysis of the influence of discharge and water temperature on the movement patterns of the fish. The active fish-tracking system recorded 1,572 fish localisations over 7months on a weekly basis for 80% of the tagged fish (37 barbel, 23 chub and 13 catfish). Compared with the catfish, barbel and chub showed wider longitudinal home ranges, more movements >1km and higher interindividual variability. The catfish preferred artificially heated habitats with less morphological diversity. The three species were more often localised in river sections with high density of woody debris. The results suggest that habitat degradation is more damaging for cyprinids in large modified rivers, while the catfish seemed less, impacted.