Effects of multiple hormonal stimulation and stripping during out-of-spawning season on sperm quality of common carp Cyprinus carpio

The availability of mature broodstock that produces high-quality gametes is one of the vital issues with fish reproduction. The effects of multiple hormonal stimulations and continuous stripping of the same individual males on spermatozoa quality are unclear. Thus, this study aimed to investigate motility parameters and seminal plasma compositions of common carp sperm during out-of-spawning continuous stripping stimulated by multiple hormonal injections. Five mature males ∼3 years old, each approximately 1.7–2.3 kg bodyweight cultured in RAS at a stable temperature of 21 °C were used in this study. Fish were treated monthly (at the beginning of each month from August to October) with carp pituitary at 1.5 mg kg−1 (b.w.) dissolved in 0.9 % (w/v) NaCl solution 24 h before milt collection. The mean sperm concentration ranged from 17.55 to 20.19 × 109 mL−1 collected during the experiments and did not significantly vary among the sampling months (F = 2.352, p = 0.1374). However, the repeated measures ANOVA showed significant effects of sampling months (F = 25.24, p = 0.0001) and individual males (F = 7.50, p = 0.0001) on the motility parameters and seminal plasma compositions, but their interaction effects were not significant (F = 1.31, p = 0.079). One-way ANOVA revealed a significant difference in spermatozoa motility (F = 10.51, p = 0.0001) and pH of the seminal plasma (F = 90.00, p = 0.0001), but did not differ in curvilinear velocity (VCL), straight-line velocity (VSL), and ionic compositions (Na+, K+, Cl-, Ca2+, total protein, and osmolality) of the seminal plasma (p > 0.05). The mean spermatozoa motility in August (88.51–94.05 %) and September (89.88–96.00 %) was significantly higher than in October (83.99–89.58 %), but spermatozoa motility was >80 % in all males for the three consecutive months. The present study indicated that multiple hormonal stimulation and continuous stripping did not suppress common carp's spermatozoa production and quality parameters.