Seasonal variability of biological and hematological characteristics of mature individuals of the Black Sea Shemaya Alburnus mento (Cyprinidae) from the Don part of the population

The results of multi-annual research studies of the pre-spawning biological and hematological characteristics of mature individuals of the Black Sea shemaya Alburnus mento, which perform anadromous migrations to the Don River in the autumn season, are presented. This species is valuable in the Azov ichthyofauna and is in the Red List of Threatened Species of the Russian Federation and the Rostov Region. Average fecundity rate of the shemaya females in the autumn anadromous migration in the pre-spawning period (22,2 thousand pcs) and the content of first-generation oocytes (31,1%) were found out. It is shown that, in the pre-spawning period, the average body weight was 125,9 and 101,9 g. body length was 21,1 and 19,5 cm, and the gonadosomatic index (GSI) was 6,3 and 3,3% for females and males respectively; it means that this species exhibits sexual dimorphism in terms of some characteristics. Relation between females fecundity and their length and weight has been estimated. Variability of the biological and hematological characteristics of individuals from the period of autumn anadromous migration to the pre-spawning period has been analyzed; verifiable increase in the gonad mass, GSI, the number of first-generation oocytes, and female fecundity has been recorded, as well as decrease in the overall body weight of the individuals of both sexes. The conclusion was made that the seasonal variability of biological and hematological characteristics gives evidence of the process of reproductive products formation and of the preparation of mature individuals to spawning, despite long period of retention (5–6 month) in the pond environment of rheophilic fish farms, which differs from the natural environment. It indicates high adaptive capacity of the individuals of this species, as well as the possibility to use shemaya individuals from autumn migration for the purposes of artificial reproduction