BIOLOGICAL CHARACTERISTICS OF PIKE (ESOX LUCIUS LINNAEUS, 1758) OF THE LOWER DNIEPER RIVER IN CURRENT CONDITIONS

Purpose. To analyze major biological characteristics of pike (Esox lucius L., 1758) stock in the lower Dnieper River in the conditions of transformed flow. Methodology. Collection of the ichthyological material was carried out in the lower Dnieper River from commercial fishing gears, including beach seines, drag seines, fyke-nets. Field, laboratory processing of samples and mathematical analysis of the obtained results were carried out according to generally accepted methods and guidelines with some assumptions regarding the duration of pike fattening directly in the lower Dnieper River. Findings. Recent years, there is an increase in the specific weight of younger age groups in the pike stock in the lower Dnieper River. Analysis of linear growth indicates on satisfactory environmental conditions for pike. Current commercial contingent of pike is based on size classes of 46?50 cm versus 22?32 cm in the first half of the last century. Reproductive properties of pike, in particular fecundity, egg size and maturity coefficients did not virtually change compared to those of the last century. Depending on linear sizes, the absolute fecundity is 32.3?155.8 thousand eggs and the maturation coefficient is 11.1?15.7%. Morphologic variability of pike in the lower Dnieper River during the period from 1980s to the present time was observed for plastic features, which characterized fin sizes. Sexual dimorphism in current conditions was observed only for maximum body depth. No significant differences for other plastic features between males and females of pike in the lower Dnieper River. Originality. The data on biological characteristics of pike stock from the lower Dnieper River have been updated. Current fecundity of females of different size groups recorded in commercial catches was been determined. An analysis of morphological variability of major plastic features of pike in the process of the transformation of the Dnieper River flow has been carried out. Practical value. The determined peculiarities of pike linear growth will allow optimizing commercial harvest for preserving the most productive part of the stock. Such measures will contribute to an increase in the commercial stock of this valuable predatory fish of the Dnieper-Bug mouth system that in turn will ensure appropriate regulation of the number of coarse non-commercial fish. This is highly important for the balanced trophic strain for valuable commercial species at early stages of their development.