Oogenesis of paliya <Emphasis Type="Italic">Salvelinus alpinus</Emphasis> complex (Salmonidae) during its breeding under fish-farm conditions

A histological study of oogenesis of paliya Salvelinus alpinus complex (from larvae aged 3 weeks after hatching to the age of 3 years and 9 months) has been carried out. The fish was bred in tanks of the Federal Center of Fish Genetics and Selection (FCFGS, Ropsha, Leningrad oblast). Three-week-old larvae had primordial cells and gonia of the first orders in rudimentary gonads. Sex differentiation was completed and development of ovarian plates started in young fish aged 3.5 months. There were already previtellogenic oocytes in fish ovaries at this age. The morphology of the circumnuclear zone in previtellogenic oocytes of all stages, which appear as the age of the fish increases, as well as the morphology of oocytes of the period of trophoplasmatic growth, are described. In FCFGS conditions, paliya females aged 3 years and 9 months did not mature or oocytes degenerated in mature females. Only after a year, normal spawn was obtained from mature females.