EFFECT OF  17ß-ESTRADIOL, OVARIAN FLUID FREE STEROIDS AND STORAGE DURATION ON GAMETE VIABILITY OF RAINBOW TROUT (Oncorhynchus mykiss)  

The effects of  storage duration and storage media include ovarian fluid (OF), ovarian fluid free steroids (OFFS) and ovarian fluid free steroids + 17ß-stradiol (OFFS+E₂) on the viability of unfertilized eggs of rainbow trout from fertilization to hatching stage were studied. In this study the percentage of eyed and hatched eggs  were used as proxies for egg viability. Unfertilized eggs were stored in relevant media at 4^oc. These eggs were fertilized  0 (i.e. control eggs fertilized prior to storage), 4, 7, 10, and 15 days after ovulation. Semen mixture was obtained from 3-year-old males. According to the results of this study, until 7 days after ovulation all the eggs in different media kept their viability, unless  the data showed a significant  decrease from 74.69±9.89 to 62.30±10.41 and from 57.39±16.75 to 43.58±16.06 for eyed and hatched eggs respectively. By 10 days after ovulation only the eggs in OF were fertilizable and kept their viability to eying 38.48±21.95 and hatching stage 16.09±9.28 and 15 days after ovulation, all the eggs lose their viability. The viability of eggs in  all media decreased in compare of control (p<0.05). The osmolality of media increased and pH decreased during the storage time.  Water uptake during hardening decreased with increase the time of storage. According to present study, unfertilized eggs of rainbow trout can be stored in OF for 10 days at 4^oc and in OFFS and OFFS+ E₂ for 7 days after ovulation, unless storage duration had a significant effect on fertility loss (P<0.05).