The growth of rudd Scardinius erythrophthalmus (Cyprinidae) in the watershed of the River Sarysu

Within Central Kazakhstan, rudd (Scardinius erythrophthalmus) inhabit a variety of types of water bodies belonging to the Ponto-Aral-Caspian ichthyogeographic province. Three samples from this water system studied in different years did not differ significantly in terms of the back-calculation of growth in body length. The studies also showed that there was also no sexual and generational variability in growth rates. The sufficiently high level of correlation of the calculated body length in adjacent generations was found, showing the constancy of the factors influencing it and the stability of the habitat as a whole. The asymptotic body length of the von Bertalanffy equation L∞ and the Pauly-Munro growth-performance index were clearly more positive for samples from the River Sarysu and the Bidaikskoe reservoir, as well as for the condition factor and the calculated weight growth. The main factor influencing the growth rate of rudd in the watershed of the Sarysu is likely to be the dynamics of the hydrological regime, which causes the appearance of a negative temperature regime in shallow waters. Comparing the results obtained across the three studies with previously published data, it is clear that the growth rates of this species in this watershed can be seen as average.