Determination of the optimal weight and density of juvenile Pikeperch (Sander lucioperca) after transfer from pond to industrial conditions

The work presents the results of studies to determine the optimal weight and stocking density of juvenile pikeperch during transfer from pond to industrial growing conditions. It is shown that larvae with an average weight of 116 mg are better adapted to transfer from ponds to pools for artificial feed than juveniles weighing 627 mg. In both cases, pikeperch fingerlings reached the weight of 1 g in 25–31 days, but pikeperch juveniles with a lower weight had higher survival rates (up to 69% vs. 20–40%), growth (average daily increase of 7,3–8,4% vs. 2,6%) and stocking density (up to 12,0 individuals per liter vs. 3,2 individuals per liter). The decrease of stocking density to 2,3 individuals per liter and its increase to 12,0 individuals per liter determined a faster growth of juveniles in the pools in the first weeks of rearing than at a stocking density of 8,6 individuals per liter, which indirectly indicates an earlier adaptation of juveniles to new conditions and the transition to an artificial diet. The survival rate of pikeperch was also higher with a reduced (2,3 individuals per liter) and increased (12,0 individuals per liter) growing density – 69 and 45%, respectively, against 37% with the stocking density of 8,6 individuals per liter. The results of pikeperch rearing at the stocking density of 12,0 individuals per liter were characterized by the highest fish productivity – 6 g/l, which is 31–67% more than in other versions of the experiment. The use of live feed (Artemia Nauplius) allowed to improve the adaptive properties of pond juveniles during their transfer to industrial conditions and increase their survival rate to 37%, against 23% compared to a one-time transfer of pikeperch to mono diets from artificial feed (with the same stocking density of 8,6 individuals per liter). The physiological analysis of pikeperch fingerlings grown in a combined (pond and industrial) way indicates the similarity of morphophysiological, biochemical and hematological parameters with pond juveniles, which indicates both the usefulness of the fishitself and the growing conditions for the needs of pike perch juveniles, including feed and feeding regimes