Evaluation of biotechnology approaches – Polyploidization and hybridization – For improvement of pikeperch (Sander lucioperca) larviculture and juvenile on-grow with special regard to morphological traits and gonadal development

Biotechnological interventions, like hybridization and polyploidization, may change aquaculture production over time, with proven benefits, improving growth, survival, feed efficiency, and reducing intracohort cannibalism. While such traits have been studied in other aquaculture studies, pikeperch (Sander lucioperca) remains underrepresented despite its increasing commercial value. Basic morphological and reproductive traits of diploid and triploid pikeperch, as well as their diploid and triploid hybrids with the Volga pikeperch (S. volgensis), were investigated under controlled conditions for up to 350 days post-hatch (DPH). This study evaluated four experimental groups: diploid pikeperch (PD), triploid pikeperch-autotriploid (PT), diploid hybrid (S. lucioperca ♀ × S. volgensis) (HD), and their triploid-allotriploid (HT). Triploidization was induced via hydrostatic pressure. Larval ploidy and hybrid status were verified. Subsequent larviculture and juvenile growth trials spanned from 6 to 47 and 89–145 days post-hatch, respectively. Hybrid larvae in both ploidy levels exhibited superior swim bladder inflation compared to diploids, but lagged in growth. Triploidization did not enhance growth performance but decreased fish viability. However, allotriploids have proven to be more vigorous than autotriploids. Gonadal analyses indicated that PD and HD developed fully functional gonads. PT histological samples showed many germ cells that did not enter meiosis, with sporadic oocytes and spermatocytes. HT displayed two gonadal phenotypes: pro-male, resembling juvenile diploid testes, and pro-female, characterized by intersex traits, likely rendering them infertile. These findings provide valuable insights into the phenotypic effects of triploidization and hybridization.