Results of growing nelma (Stenodus nelma Pallas, 1773) in recirculation aquaculture systems

Purpose. To determine the productive and biological parameters of nelma grown in a recirculation aquaculture system (RAS) as part of the development of a high-intensity technology for growing valuable cold-water objects of aquaculture in RAS with minimized effect of climatic conditions. Methodology. The study was conducted in 2021-2023 in the RAS of the fish farm STOV “Eastern Ukrainian Center for Breeding Valuable Fish Species “MZHA” (Kharkiv region, Ukraine). The material for the study were: age-0+, age-1, age-1+ and age-2+ nelma. Feeding of nelma was carried out with the starter feed of the Inicio 917 formula and the production Efiko Alfa 790, of the European manufacturer “BioMar”, according to the feeding tables, in accordance with the physiological characteristics of each age group. Feeding was carried out using automatic feeders. Findings. Growing of age-1+ nelma was carried out at a stocking density of 150 ind./m3 and water circulation in a recirculation aquaculture system of 230 L/min, the water volume in the system was 60 m3, the daily water exchange rate was 10%. According to the obtained result, fairly high average growth rates of fish were recorded. At the end of the growing period, age-1+ fish reached an average weight of 271.6±30.1 g (Cv=33.2%, fluctuations within 110-408 g) with an average body length of 33.3±0.9 cm (Cv=8.9%, fluctuations in the range of 28.0-38.2 cm), which averaged 39 kg/m3. The survival rate of age-1+ nelma in all fish tanks was more than 90%. The average value of Fulton's condition factor was at the level of 0.7±0.02 (Cv=12.4%), which is typical for this fish species. On the 1st June 2023, age-2+ nelma grown in the recirculation aquaculture system (RAS) was characterized by following parameters: average weight was 602.8±52 (Cv=26.9%, range of 480-715 g), average body length of 42,3cm, (Cv= 8.9%, range of 33-46.4cm), respectively, the body length to height index was 5.7, Fulton's condition factor was 0.8. On the 15th October 2023, age-2+ nelma grown in a RAS reached an average body weight of 992.6 g (Cv=16.0%, range of 456-1230 g) and an average body length of 44.5 cm, (Cv=7 .9%, range of 38-50cm), the average condition factor was 1.1, (Cv = 11%, range of 0.9-1.3), which indicated a high growth rate during the last 4 months Originality. A comprehensive analysis of productive and biological parameters of growing nelma in the RAS allowed obtaining original data on the growth dynamics of its different age groups were obtained. Practical Value. A technology of growing nelma in the conditions of RAS adapted to the modern state of industrial aquaculture has been developed.