Trophic ecology of the pikeperch (Sander lucioperca) in its introduced areas: a stable isotope approach in southwestern France.

During the last decades, non-native predatory fish species have been largely introduced in European lakes and rivers, calling for detailed information on the trophic ecology of co-existing native and non-native predators. The present study describes the trophic ecology of the introduced pikeperch (Sander lucioperca) in two southwestern French rivers, using stable isotope analysis. Pikeperch could be categorized as a top-predator, and had a significantly higher trophic position (TP, mean+/-SE=4.2+/-0.1) compared to other predatory fish such as the native pike (Esox lucius, TP=3.7+/-0.1) and the introduced European catfish (Silurus glanis, TP=3.8+/-0.1). Most studies of resource use in freshwaters consider predatory fish as ecologically equivalent; however, this study showed that the pikeperch occupied a higher trophic niche compared to other predatory species in the Lot and Tarn rivers (Garonne River basin). This apparent specialization may thus have consequences upon interspecific relationships within the predatory guild and upon the functional organization of biological communities.