The development of oocyte maturation competence, egg, oil globule and larval size are population-dependent in pikeperch (Sander lucioperca)

The present study tested the hypothesis that the groups of pikeperch reared in common conditions originating from base populations differing in latitude will show different gametogenesis dynamics. In February 2021, larvae were obtained from the southern population from the river Körös, Hungary – group HAKI; and the northern population from fishponds of the Czech Republic – group CZECH. Upon initial indoor rearing, fish were stocked in outdoor tanks for the next three seasons. In January 2024, two PRESEASON ten-pair groups were formed from each population and CZECH breeders exhibited significantly lower embryo survival (42.6 ± 34.5 % vs. 7.3 ± 8.7 %). In March 2024, a single SEASON batch of ten pairs of CZECH breeders was reproduced. In parallel to the in vivo trials, an in vitro maturation (IVM) assay was used to evaluate the final oocyte maturation (FOM) dynamics in both groups of PRESEASON and SEASON. CZECH fish had smaller oocytes at both spawning occasions, while the HAKI PRESEASON was similar to CZECH SEASON (933.3 ± 27.9 μm and 953.0 ± 22.0 μm, respectively). However, the latency time was shorter in CZECH PRESEASON than in HAKI PRESEASON (214.2 ± 8.1 h and 241.1 ± 24.2 h, respectively). A single disagreement in preseason IVM FOM was noticed at 60 h post-stimulation, being higher in CZECH oocytes, while a constant trend of higher FOM was noticed at each point in HAKI oocytes in the season. The CZECH group showed improved embryo survival in season (68.3 ± 26.1 %), not differing from HAKI PRESEASON. CZECH females yielded smaller eggs with smaller oil globules on both spawning occasions. It seems that the populations may preserve their gametogenesis dynamics in consecutive generations reared in different climate conditions, which could be a useful tool for hatcheries to extend the period of egg availability from a common broodstock.