Cryopreserved rainbow trout semen can be used for the fertilization of up to 8000 eggs in a single application

Here we aimed to test the fertilizing ability of cryopreserved semen of rainbow trout (Oncorhynchus mykiss) during the fertilization of between 500 and 8000 eggs, thus establishing the optimal number of eggs to use in a single application of cryopreserved semen. The cryopreservation procedure resulted in a high post-thaw sperm motility (~70%). The fertilization rates ranged from 29 to 92% and did not differ depending on the number of eggs used. However, we did detect high and significant variability in fertilization rate among the pools of cryopreserved semen. Our results show that the cryopreserved semen of rainbow trout can be used to fertilize up to 8000 eggs in a single application. Cryopreserved sperm can be potentially implemented into breeding programs based on the crossing of selected males with individual females after confirmation of the rearing performance of larvae. Further studies should now focus on the cause of the between male variability in fertilizing ability observed in this study.