Annual reproductive cycle of black rockfish Sebastes schlegeli in captivity.

The gonadal development and serum profiles of vitellogenin and sex steroids in rearing Sebastes schlegeli were monitored for one full year. Female fish began vitellogenesis from November and completed it in March. Gestation occurred from April, and parturition occurred in June. A thin chorion and scanty cortical alveoli are oogenetic peculiarities of this fish. Male fish began spermatogenesis from June, and matured in November and December. It appears that copulation occurs in November and December, and that the sperm are stored freely in the ovary during the early vitellogenic period and under the ovigerous lamellae epithelium during the late vitellogenic period. Serum vitellogenin levels in female fish had a good correlation with oocyte growth. Serum estradiol-17β (E2) levels in female fish were elevated from November to February, suggesting that E2 controls vitellogenesis. Serum 17,20β-dihydroxy-4-pregnen-3-one (DHP) in female fish increased in the late vitellogenic period, suggesting that DHP was a maturation-inducing steroid. High levels of serum DHP during gestation suggest that it may be one of the endocrine factors for maintaining gestation. Serum 11-ketotestosterone (11-KT) levels in male fish were elevated from June to October, suggesting that 11-KT controls spermatogenesis. Serum DHP in male fish had a single peak in October, suggesting that DHP plays some role in the late stages of spermatogenesis. [ABSTRACT FROM AUTHOR]