Five females having body weights between 2.133 - 3.291 Kg. were investigated over a two week period to study the ovulatory cycles. When the first ovulation began, each female was handstripped every day, the eggs collected and fertilised using sperm of the two males. The percentage rates of fertilisation and hatching were calculated every time. The results demonstrated that freshly-ovulated eggs showed a 90% fertilisation or greater, and acceptable hatching rateo Ovulated eggs retained in the ovary for one or more days presented a loss of fertilisation and 0% hatching. Three of the five females showed regular three-days ovulatory cycles. In the other two females very few eggs were colleeted and they showed no evidence of constant ovulatory rhythms. Blood samples were taken every day to study the relationship between the ovulatory cycles and the plasmatic changes of sex steroid (17beta-estradiol, testosterone, 17alfa-hydroxyprogesterone and 170', 20{3-dihydroxy-4-pregnen-3-one).

Resumen del trabajo presentado en la Broodstock Management and Egg & Larval Quality. A Science in Aquaculture International Conference, celebrada en Stirling (Escocia), del 23 al 27 de junio de 1992