REGULATION OF ARTIFICIAL REPRODUCTION IN COLOSSOMA BROCHYPOMUM

The regulation of effective accumulating temperature and feeding amount for promoting gonad maturation during spring and autumn induced breeding were studied. When the water temperature was 23. 3±1. 1℃, the effective accumulating temperatures were up to 3509. 0±164. 2℃ and 3786. 7 ±81.8℃ ·d. of female and male spawners respectively. The average spawning rate was 86. 9%, and the spawning time was about one and a half months early than that of the induced spawning under the condition of natural water temperature.When the water temperature was at 28. 1 ± 2.0℃, the effective accumulating temperatures were 2008. 8℃ and 2030.0℃ ·d. in female and male fish respectively, and 93. 2% spawning rate was got. The feeding amount per kilogram body weight of fish during autumn breeding was low than that of the fish during spring breeding, but higher in daily feeding amount.Serum 17β-oestradiol (17β-E₂) and testosterone (T) levels were measured before and after spawning. Serum 17β-E₂ level showed highly significant decrease (spring, P<0. 01 and autumn, P<0. 001) in female after spawning. The serum 17β-E₂ level increased when the spawned fish were recultured intensively. It suggested that the role of 17β-E₂ was involved in vitellogenesis and less relationship with ovulation. The serum level of T in both female and male after spawning were highly significant increase (P<0. 001 ), and it showed in connection with ovulation and spermiation.