THE EFFECT OF MEAN FINGERLING WEIGHT ON THE RESULTS OF YOUNG-OF-THE-YEAR PADDLEFISH (POLYODON SPATHULA WALBAUM) REARING

Purpose. To determine the optimum fingerling body weight during the process of young-of-the-year paddlefish (Polyodon spathula Walbaum) rearing. To adapt the existing technologies of young-of-the-year paddlefish rearing to conditions of southern Ukraine. Methodology. An experiment aimed at determining the optimum fingerling body weight when rearing young-of-the-year paddlefish have been conducted in ponds of the Dniprovsky sturgeon hatchery and six variants have been provided, where fingerling weight ranged from 0.3 g to 0.8 g, stocking density was 1.5 thousand fish/ha. Physical-chemical and hydrobiological parameters of fish rearing, growth rate dynamics and fish feeding were determined according to generally accepted methods. The results were evaluated based on individual fish weight, mortality, fish productivity, meat accumulation coefficient. Findings. Average water temperature in ponds during rearing period ranged within 18.4–29.0°. Dissolved oxygen was above 5.79 mg O2/dm3. Average seasonal biomass of zooplankton ranged from 5.39 to 7.37 g/m3. Cladocera played the main role in paddlefish nutrition. Their share in the gut content was up to 90.56%, of them Daphnia sp. composed up to 53.74%. The analysis of the studies on fish seed quality demonstrated that the weight of fingerlings during fish stocking had significant effect on final parameters of young-of-the-year paddlefish rearing. An increase in fingerling body weight from 0.3 g to 0.8 g results to an increase first of all in survival rate from 12.7% to 29.3% and fish productivity from 39.9 to 120.8 kg/ha. Better mean weight of yearling was obtained when stocking the ponds with 0.8 g fingerlings and was 278 g. Correlation coefficient between fingerling body weight during stocking and mean young-of-the-year weight was within 0.8559, survival rate — 0.9023, fish productivity — 0.9779. Originality. A scientific assessment, advisability, and possibility for using fingerling of different individual body weight for targeted rearing of young-of-the-year paddlefish have been presented. Practical value. Optimal body weights of fingerlings during young-of-the-year paddlefish rearing have been determined and recommended