Ontogenetic Diet Shift of Invasive Gibel Carp (Carassius gibelio, Bloch 1782) in Karamenderes River (Turkey)

The ontogenetic diet shift of invasive Carassius gibelio (Bloch, 1782) wasinvestigated in Karamenderes River, Turkey. The fieldwork was performedduring summer 2012, autumn 2012 and spring 2013. The fishes were caught byelectrofishing and using gill nets. Nine fork length groups were used in order toassess the ontogenetic diet shift. The gut contents were assessed by the index ofrelative importance that was calculated from the frequency of occurrence,numerical abundance, and volumetric analyses. The most abundant length groupsof C. gibelio were 18-20 cm, 6-8 cm, and 27-29 cm length groups during summer2012, autumn 2012 and spring 2013, respectively. The feeding intensity was thelowest in the length groups of 15-17 cm during summer 2012, in 3-5 cm lengthgroup in autumn 2012 and in 24-26 cm length group in spring. Seasonal variationswere observed in the ontogenetic diet shift of C. gibelio. Large specimensconsumed more animal materials during summer and more algae in autumn. Therewas not any significant niche overlap recorded between small and large specimensexcept summer. Any niche overlap between small and large specimens might beadvantageous for the establishment success of invasive Gibel carp inKaramenderes River.