Analysis of exterior indices of Russian sturgeon juveniles grown at sturgeon fish factories of the Astrakhan region

The aim of our work was to assess the exterior features of Russian sturgeon juveniles grown at sturgeon fish factories (SFF) of the Astrakhan region. In the process of research, samples of juveniles, obtained from six factories, which are conditionally divided into six groups, were studied: group I - Zhitninsky SFF, group II - Aleksandrovsky SFF, group III - Sergievsky SFF, group IV - Bertyulsky SFF, group V - Kizansky SFF and group VI - Lebyazhy SFF. Assessment of Russian sturgeon juveniles was carried out postmortally on 360 individuals with 60 instances from each factory. According to the data obtained, the following exterior indices were calculated: fatness index, runability index, high back index, long head index and caudal peduncle index. In the process of our research, it was found that the index of long-headedness showed the least variability in all the studied samples. The coefficient of variation of indicators in all six groups did not exceed 10%. The highest coefficient of variation was observed in terms of the average weight (in the studied samples it ranged from 30.0% to 67.0%) and the caudal peduncle index (from 15.0% to 20.0%). Besides, it is worth noting that the sample from group VI had the lowest level of variability among the studied groups, that indicates the uniformity of the obtained juveniles and the high quality of the fish breeding indicators of the released juveniles. In the sample of group IV, on the contrary, the highest level of variability was observed, as evidenced by the maximum values of the coefficient of variation and standard deviation for 4 of the studied indicators out of 7. At the same time, during the study, it was noted that on the quality of the released Russian sturgeon juvenile, and later on the percentage of commercial return, was influenced not only by the hydrochemical regime and the state of the natural food supply in nursery ponds, but also by the high level of inbreeding of the brood stock on sturgeon fish factories.