Comparative study of growth in Carassius gibelio (Bloch, 1782) and Rutilus rutilus (L., 1758) from two Serbian reservoirs: Multi-model analysis and inferences

Abstract We assessed growth patterns of Prussian carp Carassius gibelio (Bloch, 1782) and roach Rutilus rutilus (L., 1758) from two different types of reservoirs (lowland type vs highland type) through multi-model analysis. We applied three different fish growth models: von Bertalanffy (VBGF), Gompertz (GGF) and Robertson (RGF) growth functions and assessed the best fitting model using the Akaike's Information Criterion (AIC). Additionally, we calculated deviations from the best fitting model ( Δ i ) and Akaike weights ( w i ) for all models. The VBGF was not the best fitting model in all cases. Furthermore, in many cases more than one model was significantly supported ( Δ i w i F -statistic displayed significant differences in the best fitting growth functions between the Gruža and Međuvrsje Reservoirs for both species. As hypothesized, individuals inhabiting the calm, shallow lowland reservoir with a large surface area attained higher asymptotic lengths than individuals inhabiting narrow highland reservoir with high water flow. Fish inhabiting narrow water bodies with high water flow need to adapt specifically to these conditions since water current affects the movement of fish as well as prey encounter rate, thus smaller bodies which allow higher maneuverability appear to be favored when compared to bulkier body forms in such environments. Therefore, we assume that differences in growth patterns observed in this study predominantly present a response to the highly differential environmental conditions from the two reservoirs.