Morphobiological characteristics of common pike (Esox lucius L.) in small reservoirs of complex purpose in Sumy and Kyiv regions

The purpose of the work was to conduct a morphobiological analysis of common pike (Esox lucius L.) from two reservoirs similar in their parameters and conditions, and to determine the difference between the populations of these species due to various anthropogenic factors. The pike from the Sumy region has a more slender body, as it is indicated by displaced dorsal (5.76) and anal fins (9.19), a larger body width (2.47) and an enlarged tail stem (9.62), a more elongated head with a snout and upper jaw (6.10, 11.37, 4.9, respectively). Such signs may indicate that the pike hunts for prey that has the maximum size according to a specimen. The indicators of the pike from the Kyiv region are somewhat different and indicate that the predator makes very rapid and fairly long-distance attacks on prey, despite obstacles such as macrophytes and other aquatic vegetation, which can be evidenced by a larger width of the forehead (13.32), head height (4.16) and head height at the nape of the neck (3.56). Also, big eyes (4.91) and an enlarged lower jaw (9.89) can indicate speed and big jerks. Based on biological indicators, we can conclude that the pike from Sumy region is more fattened, which is confirmed by measurements and coefficients of its fatness. Therefore, it is fleshier, which, first of all, affects the quality of the fish as a commodity. As for the pike from the Kyiv region, it is somewhat smaller with lower fatness coefficients, which may indicate greater expenditure of energy for obtaining food. This costliness, in our opinion, is related to competition from two more predatory fish species — perch and zander, which are common in the reservoir, and possibly to the size of the reservoir itself, which is four times larger. We consider it expedient to diversify the ichthyofauna of the reservoir in the Paryshkiv village, in particular peaceful species of fish, in order to remove or reduce the trophic competition of predators.