Influence of Migrations of Some Azov-Black Sea Basin Fish Species on Their Invasion with the Nematode <i>Hysterothylacium aduncum</i> in Different Seasons

The paper examines the influence of pre-spawning and post-spawning planktophagous and ichthyophagous fish migrations on the invasion degree of nematode Hysterothylacium aduncum (Rudolphi., 1802) in the northern part of the Azov-Black Sea basin. For the first time, a decrease in the parameters of invasion with an adult nematode in herring during its wintering in the Black Sea has been shown, compared with similar indicators during the period of post-spawning migration after spawning in the Azov Sea. According to the authors, the diet change is the main cause of the difference in the invasion rate of migrating planktophagus as well as ichthyophagous fish. The authors consider that one of the indirect reasons for the differences in the invasion values of migrating fish is the inequality in salinity in disparate water areas of the northern parts of the Black and Azov Seas.