2.4. Artificial propagation
In mid-April, when the water temperature was 21 C and 24 hours before stripping, the male fish were injected intraperitoneally with a single dose with Ovaprim hormone injections at 0.1 mg/kg of their body weight. After 5 hours of injection, the water was wiped out of their body with a soft cotton cloth. To observe the free oozing of semen flow, the fish were held head up and tail down in an inclined position. During sperm collection, care was taken to pre- vent contamination by fecal matter, blood, scales, and urine, and so forth. Sperm were provided with sufficient oxygen by maintaining sufficient headspace in the collec- tion tubes (15 mL) and keeping collected milt at 4 C. Milt was inserted into 10-mL syringes and transferred into collection tubes.