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 prevent
contamination by fecal matter, blood, scales, and
urine, and so forth. Sperm were provided with sufficient
oxygen by maintaining sufficient headspace in the collection
tubes (15 mL) and keeping collected milt at 4 C. Milt
was inserted into 10-mL syringes and transferred into
collection tubes.