The growth intra-group variability of perch Perca fluviatilis L., 1758 (Percidae) from Vyacheslavsky Reservoir

The dates on back calculation of perch growth from Vyacheslavsky (Astana) reservoir located in the Akmola oblast of the Republic of Kazakhstan are presented. We studied 2 samples, separated by a time interval approximately equal to duration of one generation. The growth rates of perch in this water body are slower in comparison with previously studied populations. The calculated length of perch have changed little for four years. Sexual and generational variability of growth is not observed. There is a fairly high level of correlation between calculated parameters of body length in adjacent generations, which indicates the stability or insignificant variability of the habitat conditions of perch in the reservoir. It can also show of the immutability of the main influencing factors and their vectors of impact. Taking into account the fact that these factors are a negative, the growth rates of perch in reservoir show a tendency to decrease. Von Bertalanffy’s growth equation performed better in the 2015 sample. This was reflected in the coefficient of Poly-Munro growth efficiency and calculated (theoretical) weight growth. The decrease in the “quality” of population biological parameters indicates beginning of degradation within the group, possibly. But, now observed differences are still at an unreliable level and are characterized only as tendencies. Based on the logical analysis, the main reason for decline in growth rate was termination of commercial fishing, which upset the existing balance in the perch population and caused the so-called “neglect of fishing”.