Sexual Dimorphism and Genetic Diversity of the Carassius carassius Population in the Eutrophic Water Body of the Tura Basin

The study aimed to identify sexual differences and genetic diversity of the crucian carp Carassius carassius (Linnaeus, 1758) inhabiting a eutrophic reservoir of the Tura river basin (Western Siberia). This species has been dynamically declining in numbers in Eurasian waters in recent decades [5; 15; 16; 19]. During the study, a biological analysis of 100 individuals of the crucian carp was conducted, including the determination of morphometric characteristics and the area of erythrocyte nuclei. The study showed that this population is characterized by a short dwarf form with a sex ratio of 1: 1, where all individuals in the sample had the fourth stage of gonadal maturity. Reliable sex differences in size-weight and meristic traits were revealed. Females were distinguished by a greater commercial length and body weight, and also had reliably higher values for 55.6% of the studied meristic traits. Analysis of the erythrocyte nuclear area showed that all individuals were diploids, while sex differences in this indicator were not significant. Genetic analysis of mtDNA revealed a single CCA2 haplotype, which indicates low genetic diversity of this population. The results of the study emphasize the need to monitor changes in the population structure of golden crucian carp and develop measures to preserve this species.