Effect of postthaw storage time and sperm-to-egg ratio on fertility of cryopreserved brook trout sperm

The aim of this study was to test the influence of postthaw storage time on sperm motility parameters of brook trout (n = 9). Furthermore, we examined the effect of sperm-to-egg ratios of 300,000:1 and 600,000:1 on fertility of postthaw, cryopreserved, brook trout sperm. The application of a cryopreservation procedure produced very high postthaw sperm motility (56.8 ± 4.0%). The cryopreserved sperm of brook trout could be stored up to 60 minutes without loss of the percentage of sperm motility (52.0 ± 9.0%). The fertilization capacity of brook trout postthaw sperm was comparable with the fertilization rate of fresh semen at a sperm-to-egg ratio as low as 300,000:1 (42.4 ± 14.0% and 36.5 ± 11.0% for eyed and hatched stages, respectively). The possibility of postthaw semen storage for the prolonged time and the obtainment of high fertilization rate at low sperm-to-egg ratio can lead to the significant improvement of brook trout semen cryopreservation procedure.