Trophic interactions in a lowland river fish community invaded by European barbel Barbus barbus (Actinopterygii, Cyprinidae)

Following their invasion, non-indigenous fish can potentially exclude native fishes from their original niches through competition, or can partition in their resource use with native species to facilitate co-existence. Here, using stable isotope analysis, the trophic interactions of invasive European barbel Barbus barbus and other fishes were tested in an invaded river of relatively low fish species diversity and where no other Barbus species were present. Testing was over three distinct life stages: age 0 + ( 386 mm). There were strong patterns of isotopic niche partitioning between the juvenile fishes, with some inter-specific niche differences also apparent in 0 + fishes. For adult B. barbus and chub Squalius cephalus, however, niche convergence was evident. Within the B. barbus population, the niches of the adult fish differed significantly from the 0+ and juvenile fish, indicating considerable dietary changes with development. These results suggested that niche partitioning at the most abundant life stages were facilitating the co-existence of invasive B. barbus with other fishes in the community, with this most likely driven by inter-specific differences in functional morphology and habitat use