The effect of fish size and stocking density on the weaning success of pond-cultured pikeperch Sander lucioperca L. juveniles

The effect of initial fish size (small with TL = 40.3 +/- A 2.3 mm and W = 0.42 +/- A 0.15 g, medium with TL = 56.2 +/- A 2.7 mm and W = 1.66 +/- A 0.4 g, and big with TL = 71.0 +/- A 3.2 mm and W = 2.95 +/- A 0.65 g) and stocking density of identical fish with TL = 40.3 +/- A 2.3 mm and W = 0.42 +/- A 0.15 g (1; 2; 4; 8 fish l(-1)) on weaning success was evaluated in pond-cultured pikeperch. The trial was divided into weaning (12 days) and post-weaning (16 days) periods. Small juveniles reached significantly higher specific growth rate (SGR = 1.6 +/- A 0.2 % day(-1)) and survival rate (S = 81.7 +/- A 2.7 %) and lower cannibalism (C = 3.0 +/- A 0.75 %) compared to medium and large juveniles (SGR = 0.3-0.5 % day(-1), S = 65.3-76.5 %, C = 6.5-7.5 %) during the weaning period. The higher survival rate was found at the two higher densities (S = 72.0-79.1 %) during the weaning period. The lowest survival rate (S = 38.9 +/- A 2.7) was observed at the lowest fish density. Fish stocking density did not affect growth, condition, or cannibalism rate during the weaning period. Similar trends of growth, survival, and cannibalism of weaned juveniles were observed during the post-weaning period. A mass weaning trial verified experimental results showing small pikeperch juveniles to reach satisfactory growth rate (SGR = 1.4 +/- A 0.1 and 7.2 +/- A 0.2 % day(-1)), survival (S = 78.7 +/- A 3.0 % and 97.6 +/- A 1.0 %), and cannibalism (C = 4.0 +/- A 1.5 % and 2.5 +/- A 1.0 %) rates during the weaning and post-weaning periods. No body or fin deformities of weaned juveniles were observed.