Effect of carp pituitary homogenate (CPH) and sGnRHa (Ovaprim) on northern pike (Esox lucius) spermiation stimulation and its effect on quantity and quality of sperm

•Hormonal treatment had a positive effect on sperm maturation in northern pike, regardless of the hormonal preparation used.•The highest progressive motile sperm, straight-linear velocity and movement linearity was noted in fish treated with Ovaprim.•It was possible to collect sperm from non-hormonally manipulated fish however only a small amount of lowered sperm quality was noted.•Seminal plasma osmotic pressure is a crucial regulatory factor determining northern pike sperm quantity and quality. The effect of carp pituitary homogenate (CPH, n = 7) at a dose of 2.0 mg kg−1 and (D-Arg6, Pro9NET)-sGnRH + domperidone (Ovaprim, n = 7) at a dose of 0.5 ml kg−1 in northern pike (Esox lucius) sperm maturation under controlled conditions was examined. On the control group, 0.9% NaCl at a dose of 1.0 ml kg−1 (n = 7) was used. Sperm was collected 48 h following injection. Sperm quantity (total sperm volume, total sperm production and sperm concentration), sperm motility using the Computer-assisted sperm analysis (CASA) system and sperm and seminal plasma quality (sperm pH, seminal plasma osmotic pressure and seminal plasma pH) were determined for each male separately in each group. The results of the present study demonstrate that hormonal treatment had a positive effect on sperm maturation in northern pike, regardless of the hormonal preparation used. However, even though no differences were found in total sperm volume and total sperm production between fish injected with either CPH or Ovaprim, it should be highlighted that the highest progressive motile sperm (PRG), straight-linear velocity (VSL) and movement linearity (LIN) was noted in fish treated with Ovaprim. It was also found that it is possible to collect sperm from non-hormonally manipulated fish. However, in such a case, only a small sperm volume (around 0.1 ml) characterised by lowered PRG (below 40%) was noted. Considering the fact that only after Ovaprim application sperm motility with progressive movement of sperm above 50% was observed, the hatchery practice of collection of sperm 48 h after its application (at a dose of 0.5 ml kg−1) may be recommended.