Stable isotope analysis was used to determine which basal sources supporting native and invasive cyprinid fishes are important in a dimictic-eutrophic lake (Lake Zinav, Turkey). We sampled potential primary producers (littoral, pelagic sources and detritus), fish and macroinvertebrates from littoral and pelagic zones of the lake during spring and summer in 2013. The relative importance of basal sources assimilated by invasive (Carassiusspp.) and native fishes (Squalius cephalus, Capoeta banarescui,Cyprinu scarpio) was estimated using SIAR mixing model. Consumers such as collector-gatherer (1) (-35.33 parts per thousand) and S. cephalus, Carassiusspp., and C. carpio had more C-13 depleted (-32.12, -31.09, -31.54 parts per thousand, respectively), while C. banarescui, collector-gatherer (2), and etc. had more C-13 enriched values (-25.03, - 26.55 parts per thousand, respectively). SIAR and gut contents indicate that main energy sources were highly variable among fishes, three main sources contributed to invasive fish, but littoral sources for C. banarescui, pelagic sources for S. cephalus, and detritus and pelagic sources for C. carpiowere important. Consumer's biomass were also partially linked to detritus. Our study suggested that all species promoted coupling of pelagic and littoral pathways, and competition for resources among invasive and native fishes was likely to cause resources sharing, and to shift to suboptimal resources.