Summary The effect of selected hormonal preparations, i.e. [(D‐Ala6, Pro9‐NEt)‐mGnRH+metoclopramide] (Ovopel), [(D‐Arg6, Pro9‐NEt)‐sGnRH+domperidone] (Ovaprim), luteinizing hormone releasing hormone (LHRHa), human chorionic gonadotropine (hCG) and carp pituitary extract (CPE) on the total volume of milt (TVM, ml), volume of milt per kg of body weight (VOM, ml kg−1 b.w.), sperm concentration (×109 ml−1) and total sperm production (TSP, ×109) of dace Leuciscus leuciscus (L.) has been examined. The control group (Control) included fish which milt was taken after 0.9% NaCl injection. The parameters of sperm movement were analysed with the CASA system and included: sperm motility (MOT, %), progressive motility (PRG, %), curvilinear velocity (VCL, μm s−1) and straightlinear velocity (VSL, μm s−1) of sperm, linearity of movements (LIN = 100 × VSL/VCL,%), wobbling (WOB, %), amplitude of lateral head displacement (ALH, μm) and beat cross frequency (BCF, Hz). Milt was taken from all fish (n = 12 per group) 48 h after hormonal stimulation and selected milt and sperm parameters were determined. The best results in volume of milt was found after Ovaprim treatment and TVM and VOM values were statistically higher compared to the values recorded in the Control (P < 0.001), LHRHa (P < 0.001), hCG (P < 0.001) and Ovopel group (P < 0.05). Ovaprim treatment significantly increased also TSP values without differences only between Ovopel group. Sperm concentration was significantly lower after Ovaprim treatment compared to the Control (P < 0.001) and Ovopel (P < 0.05). In CASA parameters, no significant differences were found between MOT, PRG, LIN, WOB and BCF values depending on the hormonal preparation used (P > 0.05). The highest VCL and VSL values were recorded after LHRHa treatment but there was no statistical differences between Control, Ovaprim and CPE groups. Significant differences in ALH parameter were recorded only between LHRHa and hCG (P < 0.01).

Changes in semen quality and selected biochemical markers were analyzed during a week of spawning season of common carp Cyprinus carpio L. Semen was obtained twice, on May 30 and on June 7, and each time it was collected 24 h after hormonal stimulation using Ovopel [(D-Ala 6 , Pro 9 NEt)-mGnRH ? metoclopramide] in 1 pellet kg -1 . The total volume of semen (ml), volume of semen per kg of body weight (ml kg -1 b.w.), sperm concentration (910 9 ml -1 ), total number of sperm per kg of body weight (910 9 kg -1 b.w.), pH of semen, pH of seminal plasma, seminal plasma osmotic pressure (mOsm kg -1 ) and the total protein content in seminal plasma (mg ml -1 ) were determined. A 10 mM Tris buffer containing 100 mM NaCl with 0.5 % BSA (pH 9.0, osmolality 200 mOsm kg ), movement linearity (LIN, %), wobbling index (WOB, %), amplitude of lateral head displacement (ALH, lm) and beat cross-frequency (BCF, Hz). The volume of semen per kg of BW, total number of sperm per kg of BW and semen pH were significantly lower at the second semen sampling compared to the first semen sampling. Volume of semen at the second sampling correlated positively with CASA parameters. A lack of differences among CASA parameters between both collection periods indicates good quality of carp sperm hormonally stimulated with Ovopel twice at a 1-week interval.

NEt)-mGnRH ? metoclopramide] to male barbel Barbus barbus (L.) 6, 12 and 24 h after hormonal stimulation was analyzed. The control group (Control) during each time interval was stimulated with 0.9 % NaCl. Milt was collected from seven fish only once (n = 7) for Ovopel, Ovaprim and Control group in order to determine total volume of milt, volume of milt per kg of body weight, sperm concentration, total sperm production, seminal plasma osmotic pressure, pH of milt and pH of seminal plasma. Woynarovich's solution (68 mM NaCl ? 50 mM urea) with the addition of 0.5 % BSA (pH 7.7; 181 mOsm kg -1 ) was used as the activating liquid. Selected parameters of sperm motility (MOT %) and progressively motile sperm (%), curvilinear velocity (VCL, lm s -1 ), straight-line velocity (lm s -1), movement linearity (%), wobbling index (%), amplitude of lateral head displacement (lm) and beat cross frequency (Hz) were determined using the Computer-assisted sperm analysis system. A time of 6 h proved to be too short to obtain milt from barbel following hormonal stimulation with Ovaprim and Ovopel. Extending the time to 12 h, however, resulted in 100 % spermiation in males, regardless of hormonal preparation used for stimulation. The stimulation of spermiation in barbel is best performed using Ovopel 12 h upon application. Extending the latency period to 24 h following the application of this preparation results in a significant decrease in the volume of milt obtained, sperm count and motility parameters, including MOT and VCL, which may influence sperm fertilization ability.