The aim of the study was to compare the effects of rearing juvenile pikeperch in two types of tanks used widely in hatcheries; the tanks had either round (group O) or square (group K) bottoms. Two experiments were conducted. In experiment I, the mean initial body weight (m.c.) of the fish was 0.33 g, and in experiment II it was 1.76 g. The factor studied (tank shape) had a significant impact on the fish growth rates and feed conversion ratio (FCR) and protein efficiency ratio (PER). The results obtained in the two experiments differed. With the smaller pikeperch (experiment I) better results were obtained in group O, while with the larger fish (experiment II) better results were obtained in group K. No differences among groups in fish condition or stock survival were noted. The results indicate that smaller juvenile pikeperch (m.c. ≥ 0.3 g) should be reared in round-bottomed tanks, while larger fish (m.c. ≥ 2g) should be reared in square-bottomed tanks. Using the appropriate tanks for rearing particular size groups of pikeperch could potentially result in increased growth and more effective feed conversion ratios, thus shortening rearing times and lowering production costs.
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