327first sexual maturity at a highly variable age (6-12 years), and the ovarian maturation rates within an age group are dependent on growth and body size. After the first spawning, the majority of white sturgeon males and females exhibit annual and biennial reproductive cycles, respectively. The environmental seasonality (temperature and photoperiod) plays an important role in synchronization of gonadal development and spawning. Reproductive management. The efficient utilization of sturgeon broodstock for either breeding or caviar production requires optimal environment and special techniques for reproductive management. New generations of the broodstocks are usually selected from the "production fish", at the age 3-4 years. Fish are sexed (by the surgical examination of their gonads) and marked. Mature males are selected for spawning by their external appearance, while the females are sampled each winter starting from the age 6-7 years, to segregate postvitellogenic, midvitellogenic, and previtellogenic (or early vitellogenic) stages of the ovarian maturity. Ripe females and males are held in cool water, chilled or natural, for at least 2 months before spawning. The optimal stage of ovarian development for hormonally induced spawning is predicted by the rate of germinal vesicle migration and verified by standardized egg maturation bioassay. Spermiation and ovulation are induced by the common carp pituitary extracts or GnRH analogs. The best performance (practically 100 % ovulatorq. response, 90 % fertility, and 80 ' YO hatchability) was recently achieved by the administration of GnRH analog in combination with doparnine antagonist (pimozide or domperidone). Current studies. With thl: improvements in reproductive management and spawning performance of domestic broodstocks, several other studies are currently initiated that will encompass a broader spectrum of applied research including reproductive physiology, selective breeding, health management, and identification of genetic :sex and monosex culture.

Extended Abstracts: Environmental and husbandry factors in sturgeon culture resistance to stress and intoxication, a reaction could only occur only after the ontogenesis of certain interactions in the endocrine system (Trenkler et al., tihis issue). Indirect evidence of bPP involvement in hypothalamo-pituitw interactions in sturgeon fry was the melanophore reaction, which was connected with inhibition of melanocyte-stimulating hormone secretion. The exact mechanism of bPP action in sturgeons needs further investigation. ReferenceKovalenko R. I., Zagustina L A,, Stepanova N. A. On mechanisms of antigonadotropic action of pineal polypeptides. Vopr. Of Neuroendocrinol., N 24, Lmingrad State Univ., 1983, p. 46-52.