Growth and Development Dynamic of the Lena Population Siberian Sturgeon (Acipenser baerii Brandt, 1869) Bred in a Recirculating Aquaculture System

Siberian sturgeon (<i>Acipenser baerii</i> Brandt, 1869), characterized by its rapid mass accumulation and high survival rate under industrial breeding conditions, is one of the most promising aquacultural species. This research aimed to study the growth and development of farmed Siberian sturgeon (<i>Acipenser baerii</i> Brandt, 1869) to improve breeding programs. This research was conducted at the Federal Research Center for Animal Husbandry named after Academy Member L.K. Ernst and focused on the Lena population broodstock of Siberian sturgeon of the April 2022 generation (<i>n</i> = 98), grown in a recirculating aquaculture system (RAS). The experiment took into account body weight (W, g) and eleven morphological measurements: L-absolute length (cm); LR-fish body length increase (cm/day); l-commercial length (cm); L2-fork length (cm); HL-head length (cm); PV-pectoventral distance (cm); VA-ventroanal distance (cm); pl1-peduncle length (cm); H-body height (cm); h-peduncle height (cm); SC-body thickness (cm); GC-body circumference (cm); and Cc-peduncle circumference (cm). These measurements were taken from the same sample of fish at five different time points, all belonging to the same generation and approximately the same age. Measurements were taken every 3 to 9 months: 1 y (group G1), 1 y. 5 m. (group G2), 2 y. 2 m. (group G3), 2 y. 5 m. (group G4), 3 y. 2 m. (group G5), and 3 y. 5 m. (group G6). To evaluate the rate of growth and development, relative speed of growth (SGR) and relative speed of lengthening (SLR) during the observation period were determined. To characterize the fish's exterior, we evaluated Fulton's condition factor (KF) and the leanness index (Q). With increasing age, there was a significant (<i>p</i> < 0.01) decline in both SGR (from 0.454 to 0.065 g%/day) and SLR (from 0.132 to 0.028 cm%/day), which reflects changes in the fish's physiological processes tied to the transition from the growth phase to the puberty phase. Relatively large variability was observed in body weight (C_v = 19.7-30.4%) compared to morphological measurements (C_v = 5.7-14.9%). Correlations between morphological measurements and the body weight of the fish varied from low to high (r = 0.22-0.97). Equations that allow for very precise (coefficient of determination R² = 0.800-0.933) estimation of the fish's body weight based on morphological measurements were developed. The most preferable predictors were measurements of H (R² = 0.931), SC (R² = 0.933), and L2 (R² = 0.930). These morphological measurements are promising candidates for future development of contactless live weight detection using computer vision and machine learning algorithms. The study of live weight conjugacy at different ages showed that the best time to use this measurement to select fish for reproduction is at the age of 2 y. 2 m. or older. Acquired data can be used for the development and improvement of programs for the selection and breeding of Siberian sturgeon grown in a recirculating aquaculture system.