Fertilization in farmed and wild maraena whitefish (Coregonus maraena, Bloch, 1779) in different activation solutions

This study compared the reproductive performance of farmed and wild maraena whitefish (Coregonus maraena) and fertilization rates of sperm activated with three activation solutions (AS): Billard solution (BS: 20 mM Tris containing 1 mM CaCl₂, 30 mM glycine, and 154 mM NaCl; pH 9.0; osmolality 330 mOsm·kg⁻¹), saline solution (SS: 20 mM Tris containing 30 mM NaCl; pH 8.5; 80 mOsm·kg⁻¹), and lake water (LW: pH 7.5; 20 mOsm·kg⁻¹). Although no significant differences were observed between farmed and wild fish in basic reproductive traits (egg weight, pseudogonado-somatic index, sperm volume, sperm production), notable contrasts emerged in sperm kinetics and fertilization success. Progressive motility (PRG), curvilinear velocity (VCL), straight-line velocity (VSL), wobble (WOB), and beat cross frequency (BCF) changed significantly depending on the AS used for sperm activation in both farmed and wild whitefish. There were no significant differences in fertilization rate between farmed and wild fish after BS used. However, compared to farmed, in wild fish, fertilization rates were higher with SS and LW, despite lower sperm motility under these conditions. Linear regression analysis revealed significant negative correlations between high sperm velocity and fertilization success in wild males after LW activation, suggesting that excessive motility may deplete sperm energy reserves prematurely. These findings highlight that optimal, rather than maximal, motility may be more critical for successful fertilization in maraena whitefish particularly in wild stocks. However, this hypothesis requires further research.