Inducing out-of-season spermiation in fish can be achieved through both hormonal treatments and environmental manipulations. This method separates reproduction from seasonal limitations, facilitating effective broodstock management and supporting year-round aquaculture production. This study aims to evaluate the effectiveness of LHRHa2 administration in the induction of out-of-season spermiation in sterlet Acipenser ruthenus. Fifteen male sterlets, with an average weight of 1106.0 ± 125.5 g, were divided into two groups and injected with LHRHa2 at a dose of zero (control, n=5) and 2.0 (LHRHa2, n=10) µg kg^-1 of body weight. Sperm was collected 24 hours post-injections using a catheter. The study was conducted in November at a water temperature of 14.1 ± 0.36 C°. Blood samples were also taken from the fish to measure total protein (TP), hematocrit value (HCT), and plasma testosterone (T). The results indicated that spermiation success in the LHRHa2 treatment was 60%, which was significantly different (P < 0.05) from the control group, where no fish (0%) achieved spermiation. The mean sperm volume, spermatocrit, spermatozoa motility, and motility duration in LHRHa2 treatment were 3.9 ± 1.9 mL, 2.0 ± 0.3 %, 9.0 ± 3.8 %, and 64.0 ± 3.2 s, respectively. The highest T level was recorded in the LHRHa2 treatment, which was 7.07 ± 0.14 ng mL^-1 (P < 0.05). No significant differences were found in HCT and TP content between groups (P > 0.05). The study results showed that hormonal treatment can induce spermiation in the sterlet outside of the spawning season, although the collected sperm does not have acceptable quality. Considering the observed effects on plasma T level and sperm quality parameters, altering the hormonal treatment strategy may lead to better outcomes for out-of-season induction of male sterlet broodstock. Consequently, increasing the dose and frequency of hormonal injections can be considered in future studies.

Artificial reproduction; Broodstock management; Hormonal treatment; Motility; Semen; Stimulation