Effects of Stripping Frequency on Semen Quality of Endangered Caspian Brown Trout, Salmo trutta caspius

Problem statement: Because of dramatic declines in stocks of endangered Caspian brown trout males, Salmo trutta caspius in Caspian Sea, each male brooder is stripped indispensably more than once during the spawning season in other to artificial insemination in hatchery. The aim of the present study was to assay the changes of indicators of semen quality (sperm motility, sperm production, semen volume and chemical composition of seminal fluid) during these sequential strippings. Approach: The 11 tagged males were stripped four times every 12-14 days with beginning of spermiation period (2 December 2008) towards its end (10 January 2008). One-way Analysis Of Variance (ANOVA) was employed to analyze differences between means of semen parameters. Also, the relationships between semen parameters were tested using the bivariate correlation coefficients of Pearson. Results: The semen volume, sperm density, osmolality and the concentrations of Na⁺, Cl^-, K⁺, Ca²⁺, Mg²⁺ and total protein gradually decreased whereas the values of glucose and triglyceride had no significant changes during sequential strippings. Also, the values of semen pH, the percentage (5s post-activation) and duration of motility were statistically stable until third stripping but a decrease was recorded for these parameters in the fourth stripping. As well as, significant positive correlations were found for sperm density vs. K⁺, Cl^-, Na⁺, Ca²⁺, Mg²⁺, total protein, spermatocrit; the percentage of motile spermatozoa Vs Ca²⁺, Mg²⁺, K⁺, Cl^-, Na⁺, total protein and also the duration of motility Vs K⁺, Cl^-, total protein and pH. Conclusion: The semen quality of Caspian brown trout males decrease in successive strippings during spawning season. Also, the knowledge on values and correlations between the sperm motility characteristics and the composition of seminal fluid could be useful to formulation of a species-specific extender solution for cryopreservation of semen of Caspian brown trout.