Mendryshora P. Aquaculture-biological peculiarities of the replacement-brood stock of the rainbow trout formed in the conditions of the sndustrial trout farm with combine water supply.

The dissertation is devoted to the study of aquaculture-biological peculiarities and efficiency of the use of age-2+ - 3+ brood rainbow trout adapted to instable rearing conditions.genotypes of amplicon combinations were detected. At the same time, fish were characterized by a relatively low level of erythrocytes (P<0.05) and low frequency of erythrocytes with micronuclei and binucleated lymphocytes. The performed studies showed that 10.4% of females reached sexual maturity at age-2. At the same time, the mean weight of females with Smith body length of 37.5±3.46 cm was 720.0±157.96 g. Working fecundity with individual egg parameters of 37.3 mg, 3.9 mm, was 2.3 thousand eggs. The weight of the produced eggs was 84.4 g. The fertilization rate was within 84.9 – 92.7%, survival rate during incubation was 60.2%. The obtained offspring from these brood fish were characterized by moderate values. The mean body weight of 45 day larvae was 974.5 mg, survival rate – 47.7%. The productive and reproductive features of age-3-4 brood fish compared to the existing brood stock were improved by 26.1% and 30.6%, respectively. The productive and reproductive parameters of age-3+ females were higher compared to age-2+ females by 46.8 and 31.1%. It allowed producing more viable offspring and, as a result, increasing the profitability level of the fish farm up to 23.8%. Compared to females, age-2+ males had lower mean weight by 25.0%. The ejaculate volume was within 8.3-10.0 cm3. The weight of age-3+ males was also lower than that of females, however, the variability coefficient was reduced from 13.8 to 7.8%. The mean body weight of age-4+ females was 3.8 kg with a range from 3.0 to 5.8 kg. At the same time, the mean working fecundity was 4.5 thousand eggs. Thus, Age-4+ females did not significantly exceeded age-3+ females by working fecundity, however, they had higher values by individual parameters, therefore it is advisable to use age-4+ females in table egg production.