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Spawning substrate is a critical factor in reproduction of commercially valuable percids. Substrate preferences of pikeperch Sander lucioperca were investigated using three types of artificial spawning substrates: long fibred brush, artificial turf and smooth plastic. There was a significantly higher preference for the brush nest, with thick rigid structures, than for artificial turf, while plastic nests remained unoccupied.The majority of pikeperch pairs (94.4%) spawned within 14 days of the beginning of the experiment. No difference was observed between substrates in time from stocking of fish to nest occupation and spawning. After egg laying, nests were moved to controlled conditions of a recirculation aquaculture system for incubation. Hatching rate and larva production did not differ significantly among tested substrates. Either used substrate was suitable for spawning and incubation in a recirculation aquaculture system. Obtained results can be used for semi-artificial reproduction as well as for the support and control of wild pikeperch stocks in natural habitats. K E Y W O R D S artificial nest, broodstock, egg incubation, reproduction, Sander lucioperca ). Information about substrate selectivity and the minimum quantity of suitable spawning grounds How to cite this article: Malinovskyi O, Veselý L, Blecha M, Křišťan J, Policar T. The substrate selection and spawning behaviour of pikeperch Sander lucioperca L. broodstock under pond conditions. Aquac Res. 2018;49:3541-3547.

The aim of the present study was to study spawning stimulation in artificial reproduction of females pikeperch (Sander lucioperca L.) using ''Chorulon'' containing the human chorionic gonadotropin (hCG) and compare with ''Supergestran'' containing a mammalian GnRH ([D-Ala 6 ]GnRHProNhet) analogue. The females were divided into eleven experimental groups and injected with hCG at 250, 500, 750, and 1 000 IU kg -1 body weight (BW) and mGnRHa at 1, 2.5, 5, 10, 25, and 50 lg kg -1 BW. In all treatments, a single intramuscular injection of hormone was performed. Control group was injected with 0.9 % NaCl, 0.9 cm 3 kg -1 BW. The average percentages of ovulating females were 88.5 ± 12.3 and 80.8 ± 10.9 % in hCG-and mGnRHa-treated groups, respectively. The average diameter of eggs was 0.95 ± 0.06 and 0.98 ± 0.06 mm in hCG-and mGnRHatreated groups, respectively. Neither ovulation rate nor diameter of egg was statistically differed among hormonally treated groups. Statistical difference was observed only in hatching rate, where the average were 73.6 ± 14.4 and 50.6 ± 17.7 % in hCG and mGnRHa-treated groups, respectively. Among hormonally treated groups, the best results were observed in groups treated with hCG at 500 and 750 IU kg -1 and in groups treated with mGnRHa at 25 lg kg -1 . No ovulation was observed in the control group. This study indicated successful ovulation in pikeperch using a single intramuscular injection of hCG or mGnRHa analogue.

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Propagation of pikeperch Sander lucioperca by semi-artificial management was investigated using hormonal induction to better understand the effect of hormonal treatment of both sexes. Fourteen pairs of pikeperch brood fish were divided into two groups (seven pairs in each group). Seven females in Group A and both sexes in Group B were hormonally injected with 500 IU of hCG per kg. Each pair of brood fish was held separately in a 300-l circular tank with an added spawning material on the bottom. Brood fish were removed from the tanks on the day after spawning; three-hundred randomly selected eggs were removed from the spawning nests and transferred to 250 ml plastic incubators. Sperm samples were collected from males in individual 1-ml syringes. Significant differences in fertilization rate (Group A 59.5%, Group B 80.4%), hatching rate (Group A 51.2%, Group B 71.6%), and number of larvae produced per female (Group A 49 429, Group B 122 000) were observed. Differences were attributable to sperm quality, primarily volume (Group A 0.16 ml, Group B 0.64 ml), and duration of spermatozoa motility (Group A 59.5 s, Group B 97.7 s). Hormone treatment of both sexes is beneficial for pikeperch semi-artificial reproduction by inducing ovulation and improving milt production and spermatozoa quality, fertilization and hatching rate, all contributing to a higher number of produced larvae.