Prey size selectivity of pikeperch (Sander Lucioperca L.) fed with topmouth gudgeon (Pseudorasbora Parva Temminck & Schlegel)

Abstract. The aim of this study is to examine the size selectivity of the pikeperch fed with one of the most widespread weed fish in fish farms, such as topmouth gudgeon (Pseudorasbora parva Temminck & Schlegel). Topmouth gudgeon (Pseudorasbora parva Temminck & Schlegel), separated in two size groups: large - group 1 (body weight of the specimens 8.63 ± 2.68 g, total length 9.58 ± 0.92 cm, and height of the body 2.06 ± 0.33 cm) and small - group 2 (body weight of the specimens 1.10 ± 0.36 g, average total body length of 5 ± 0.62 cm, and height of 0.85 ± 0.13 cm), were used for prey. The experiment was carried out under controlled laboratory conditions, in the course of 40 days, in 7 tanks. One pikeperch and 10 topmouth gudgeons from both size groups, in total 20 preys were placed in each tank. During the experimental period it was observed that pikeperch preferred to feed on smaller individuals, the difference in the number of consumed small and large fish is approximately 2 times (70 to 34, respectively)