GROWTH OF THE NORTH AMERICAN STURGEON (POLYODON SPATHULA) DURING THE POST-EMBRYONIC DEVELOPMENT PERIOD IN PROTECTED AREAS.

The article includes the results obtained in the growth experiments during the postembryonic development period of the North American sturgeon species Polyodon spathula. The experiments took place in the years 2020 and 2021. Sturgeon larvae aged 5 days old, obtained through artificial reproduction at SCDP Nucet, were stocked and raised until the age of 35 days in two variants, in concrete tanks (useful volume -120 m³/tank), located in the pilot station intended for fish culture experiments from the SCDP Nucet genetic library. The experimental variants consisted in testing the support capacity of the tanks when stocked with sturgeon larvae in densities of 40,000 ex/tank, respectively 333 specimens/m³ (V1); and 20,000 ex/tank respectively, 166 ex/m³ (V2). The sturgeon larvae were fed with zooplankton (Moina sp., Daphnia sp.) and artificial feed. Feeding regime was found to contribute significantly to final size and growth rate. In variant 1 (V1) sturgeon fry with an average mass of 7.4 g/ex. were obtained (survival rate of 30.3 %) and in the second variant the sturgeon fry recorded an average mass of 9.8 g/ex. (survival rate 48.4%). The differences in survival between the two variants of the rearing experiments were due to the fact that the adaptation to artificial feed was made more difficult. Also, overcrowding causes typical manifestations that consist in the appearance of large differences between individuals that favor cannibalism. [ABSTRACT FROM AUTHOR]