Plasma gonadotropin , estradiol , and vitellogenin and gonad phosvitin levels in relation to the seasonal reproductive cycles of female brown trout

Profiles for plasma gonadotropin, estradiol, and vitellogenin were obtained in female brown trout during the seasonal reproductive cycle. The accumulation of yolk lipophosphoprotein (phosvitin) in the gonad was also followed. Plasma estradiol and vitellogenin concentrations rose progressively and parallel increases in ovary yolk phosvitin were observed. Gonad development continued while plasma gonadotropin levels remained low and unchanged until oocyte maturation was underway. LH-RH treatment failed to stimulate vitellogenesis in fish in the early stages of the reproductive cycle ; how-