It was made the fi sh-biological assessment of yearlings carp hybrids obtained as a result of crossings of the Nivkovsky plant line of the small-scaled internal breed type of the Ukrainian Ramov breed and the Nivkovsky internal breed type of the Ukrainian scaly breed. The studies were carried out on the basis of the Institute of Fisheriesdepartment of the NAAS, Ukraine "Nivki", TOV "Skvirapleribribosp" and the laboratory of the Department of Production and Processing of Fish Products of the Belotserkovsky NAU according to practical standard in fi sh farming. As a control group, there were used carps of the Nivkovsky internal breed of Ukrainian scaly breed, with a total planting density of 30 thousand specimens. / ha. The research ponds were stocked with three-day larvae in early June. According to the content of the main cations and anions, nutrients and organic matter, the water of the research reservoirs of the Squirapleribribosp Ltd. for the period of the experiment corresponded to the existing standards. The quantitative and qualitative values of the indicators of the natural forage base were at the level of requirements for intensive rearing of young carp in pond farms. The growth rate of yearlings of the control group until the end of July was slightly higher than the studied group of carps hybrids by the average population values of the body mass index. The average body weight of yearlings in the control pond with the origin of LF * LF was at the moment of the experiment 7.3 ± 0.5 g, for carps of the origin of LF * NMF - 6.8 ± 0.6 g. At the end of September, the value for this indicator was at the level of 25.5 ± 1.6 g and 27.0 ± 2.0 g, respectively, for the control and the group of crossbreeds. The indices of heterosis in yearlings of carps hybrids had positive values accordance with all fi sh and biological indicators relative to their parental forms: by average weight - 106.7%, output - 111.5%, and fi sh production - 118.1%. It was established that a mixture of carps of the NCHK * NMK group have high cold resistance and winter hardiness, which are characteristic of the parent form of the Nivka lowscale carps. Key words: carp, breeding, Nivkovsky scaly, Nivkovsky scaly, yearlings, heterosis index, fi sh-biological indicators, winter hardiness.