Changes in fertility of rainbow trout eggs retained in coelom

Effects of prolonged retention time of ovulated eggs in the parental coelom on fertilization success were studied in rainbow trout Oncorhynchus mykiss using cryopreserved sperm with a uniform fertilizing ability. Proportions of successful fertilization, eyed eggs and hatched alevins were examined at different time periods up to a retention time of 14 days beyond the ordinary stripping time, and were compared with eggs incubated in artificial coelomic fluids (ACF). Eggs that were retained longer in the coelom showed gradual decreases in all the proportions of successful fertilization, eyed eggs and hatched alevins. The progress of cleavage after fertilization slowed with prolonged retention times. Eggs incubated in ACF lost their fertilizing ability much sooner than those retained in the coelom. The hatching rate of eggs retained for 2 weeks in coelom was 36%, while it was 1% in those eggs incubated for 4 days in ACF. Thus, eggs retained in the coelom showed higher fertilization success than those incubated in ACF.