Seasonal variation in trophic niches and niche overlap between native and introduced cyprinid fishes

Abstract It is critical to understand the potential effects of non-native species, especially on ecologically similar native species, and to reveal their trophic relationships. Cyprinid invasive fishes, Carassius gibelio, and translocated fish Cyprinus carpio has been introduced to the Karacaören I reservoir located in the upstream reach of the Aksu River basin. Karacaören reservoir is also an important local habitat for native Cyprinid fishes, Capoeta antalyensis and Squalius fellowesii. In this study, we evaluated the trophic structure and interspecies trophic interactions (as isotopic niches and niche overlaps) of these Cyprinid fish using stable C and N isotopes analysis as measured by Isotope Ratio Mass Spectrometer. While equally all food sources contributed to the biomass of all fish species in the summer, their biomass is supported by more specialized sources in the winter season. Our results revealed increased niche breadth with increased niche overlap between C. antalyensis and C. gibelio, and C. carpio, and among C. gibelio and C. carpio in the summer, while decreased niche breadth with decreased niche overlap in the winter season. Interspecific competition has led to trophic niche divergence, which may facilitate the coexistence of native species with introduced fishes. Non-native fish were determined to have larger niche widths, which may contribute to their invasion success.