COMPARISON OF EFFICIENCIES OF USING TRAINER FISH AND SHAPE OR TASTE MODIFIED FEED FOR ENCHANCING DIRECT WEANING OF PIKEPERCH (Sander lucioperca L.) YEARLINGS ON DRY FEED

Two practical methods aimed at the enhancement of efficiencies of weaning pond-raised pikeperch (Sander lucioperca L.) yearlings on dry feed were compared in two consecutive experiments. The first method was applying pellet-feeding fish as trainers/teachers for naive fish. As trainers, either pikeperch or perch (Perca fluviatilis L.) were used. The treatments and control (without trainer fish) were run in triplicates (9 aquaria, 40 fish/aquarium). Pikeperch yearlings were not able to learn to eat dry feed by social learning. In contrast, the presence of trainers decreased the success of weaning of naive fingerlings non-significantly (2.2% with pikeperch trainers; 7.8% with perch trainers; 8.3 % with only naive fish). The second method was to modify the taste and shape of the pellet. Bullet-form feed pellets were ground and reshaped as “artificial blood worms” (ABW). ABW were flavored either by Chironomus mixture or by a commercial aroma. Non-flavored ABW served as a control. Commercial aroma flavored ABW significantly increased the percentage of weaned fish (16.7%) in comparison to the bloodworm flavored (12.2%) and non-flavored (4.4%) ones.