Artificial reproduction stands as an essential source of sturgeon progeny for restocking, commercial production, or research. However, a fraction of offspring with altered ploidy levels often arises unintentionally in sturgeon hatcheries, usually for no obvious reason. Ploidy-abnormal individuals exhibit impaired physiology and reproduction, making their occurrence undesirable for both sturgeon farmers and conservationists..We conducted three experiments to test whether the temperature for holding females before reproduction (THF) contributes to the incidence of ploidy abnormalities in sterlet. The eggs were obtained at different THFs within 2h post-ovulation and fertilized within 30 min; ploidy was analysed in prelarvae. In Experiment 1, we worked with pooled batches of eggs that were collected at a wide range of THFs: 10,12,14,15,16,18, and 20 °C. Based on the results, Experiment 2 was designed to confirm the potential of some THFs for increased production of ploidy-abnormal progeny using an individual fertilization scheme. In Experiment 3, THF that previously yielded many abnormal individuals was combined with in vitro egg ageing for 0, 3, and 8h and two fertilization environments: 10⁵ and 10⁶ spermatozoa/egg to compare ploidy structure under various fertilization conditions. In Experiment 1, we observed that THFs 10–16 °C resulted in low incidence of ploidy abnormalities, while THFs 18 and 20°C were associated with significantly higher occurrences of spontaneous triploids. In Experiment 2, certain females held at 18 and 20 °C showed a strong tendency to produce triploid progeny, with the highest proportion exceeding 50%. In Experiment 3, varying fertilization conditions did not elevate the incidences of triploidy; however, triploidy remained extremely high (over 70%) in three out of four females held at 18 °C. We conclude that holding sterlet female broodstock at a temperature of 18 °C or higher should be avoided due to its unpredictable effect on the incidence of spontaneous triploidy.

reproduction, triploidy