Biotechnological aspects of growing white Dniester crayfish (Pontastacus eichwaldi bessarabicus Brodsky, 1967) seeds in RAS conditions

Purpose. To determine some basic technological parameters (temperature regime, stocking density, rations and type of feeds) for growing white Dniester crayfish (Pontastacus eichwaldi bessarabicus Brodsky, 1967) at the early stages of ontogenesis in a recirculation aquaculture system (RAS). Methodology. The study was conducted in 2022–2025. The material was collected during expeditions to the Dniester Estuary and the Danube lakes Yalpug and Kugurluy using commercial fyke nets. The raw weight of larvae and juveniles was determined on analytical scales VL-220M and electronic scales OHAUS SPU, after drying with filter paper. Linear dimensions were recorded using an eyepiece micrometer under an MBS-10 microscope, and for older age groups, using a caliper or ruler. Express analysis of hydrochemical parameters was carried out using the “ECOTEST-2000 T” devices (O₂, NO₂-, NO₃-, NH₄+, phosphates), the “Azha-101M” thermo-oximeter (TOC, O₂) and the pH-meter-150 M. Biological analysis was performed at the laboratory of the Department of Aquatic Bioresources and Aquaculture of I. I. Mechnikov Odessa National University. The effect of keeping conditions (hydrochemical regime, rations, and stocking density) on the survival, growth, and development of larvae and early juveniles of the Dniester white crayfish was determined. Findings. The main biotechnological parameters of growing juvenile white Dniester crayfish in a RAS have been determined. The effectiveness of cultivation depends on the optimization of the hydrochemical regime, stocking density and feeding rations at different stages of ontogenesis. The best growth and fattening results were provided by artificial feeds with 40–45% protein with three-time feeding, which significantly (p < 0.05) exceeded those of the groups receiving natural or mixed feeds. The data obtained became the basis for developing technical parameters of the production scheme and forming technological regulations for growing crayfish seeds in RAS. Originality. For the first time, the effect of hydrochemical parameters, stocking density, type of feed and feeding regime on the survival, growth and fattening of juvenile white Dniester crayfish reared in a RAS was experimentally investigated. Biotechnical standards for growing white Dniester crayfish seeds have been established, which can be used as the basis for technological regulations for mass cultivation in the RAS. Practical Value. Consists in creating scientifically sound foundations for an effective technology for mass cultivation of white Dniester crayfish seeds in RAS. The established optimal hydrochemical parameters, stocking density and feeding regimes ensure high survival, stable biomass growth and reduce losses from stress factors, pathologies and cannibalism. The proposed biotechnical solutions can be used for the design of industrial facilities, the restoration of populations in the Dniester estuary and Danube lakes, as well as in the training of specialists in hydrobiology, ichthyology and fish farming. Keywords: white Dniester crayfish, RAS, stocking density, feeding, survival, growth, biotechnology.