Changes in Sperm Quality of Silver (Hypophthalmichthys molitrix) and Bighead Carps (Hypophthalmichthys nobilis) during the Spawning Season

This study investigated the changes in spermatological parameters and biochemical composition of the seminal plasma of silver carp Hypophthalmichthys molitrix and bighead carp Hypophthalmichthys nobilis across three spawning seasons (early, mid and late). While silver carp had similar levels of motile sperm in early and mid seasons (early: 96±1%; mid: 95±1%), highest motile sperm in bighead carp was found only in the early season (95±1%). Sperm concentration in the three spawning seasons were 3.15±0.02 ×10^9 mL^-1 (early); 2.91±0.04 ×10^9 mL^-1 (mid); 2.60±0.14 ×10^9 mL^-1 (late) in silver carp and 2.96±0.03 ×10^9 mL^-1 (early); 2.79±0.02 ×10^9 mL^-1 (mid); 2.65±0.12 ×10^9 mL^-1 (late) in bighead carp. In silver carp, fertilization rate observed across spawning seasons were 75±3% (early); 61±1% (mid); 61±2% (late). However, drastic changes in fertilizability was observed in bighead carp (early: 79±3%; mid: 60±3% and late: 25±2%). Of the seminal plasma components, chloride and total protein levels were significantly changed in both fishes over seasons. The results of this study have implications in improving the quality of fish seed by improving the quality of fish sperm.