Population Growth and Age Structure of the Pikeperch Sander lucioperca (Percidae) from Lake Necheritsa (Sebezhsky National Park, Pskov Oblast, Sebezhsky District)

The size, age, and sex structures of pikeperch Sander (L.) from Lake Necheritsa (Sebezhsky National Park) have been studied, as has the linear growth using back-calculation according to the Leo direct dependence function. The growth of pikeperch is described formally by linear equation L(t) = 5.4x + 0.2 (cm). The length frequencies of individual age groups are normally distributed, which corresponds to ideas about linear fish growth. The population is represented by 13 age classes; the maximum length of an individual in the sample is 872 mm. The analysis of the diet showed the presence of 6 mass fish species observed in the catch, including the young pikeperch; the ratios of individual species in the diet and the sample indicates an absence of electivity of nutrition. According to the estimates, the proportion of pikeperch in the ichthyocenosis in the period 1989–2022 in Lake Necheritsa has increased ∼8 times. A comparative analysis of the linear growth of pikeperch from populations of different regions under environmental conditions, differing in a number of values of key parameters, is carried out. Growth rates of pikeperch from southern populations are generally higher and more consistent with asymptotic growth, while the size limits and life expectancy are generally higher in northern populations. A hypothesis has been tested about the causes of differences in the nature of linear growth.