**3. Conclusion**

In conclusion, the fertilizing capacity and egg hatchability were not significantly reduced by the post-thaw sperm treated with 12-21%DMSO, although the post-thaw sperm quality was influenced during the freezing and thaw process in motility, ultrastructure and mitochondrial function. The cryopreservation protocol used for red seabream sperm should be of great value for the establishment of sperm banks and assessment of ultrastructure and flow cytometry facilitated identification of damaged sperm; However, the exact nature of cryodamage to fish sperm are not yet fully understood. Sperm motility, structure integrity and mitochondrion function were damaged with different extent, although the fertilization capacity of cryopreserved sperm was not changed. There are many questions need to answer, how does the cryodamage reduce the sperm motility duration? If the cryodamages influence the gene expression and the embryo and larvae development? how to improve the post-thaw sperm quality by optimize the cryopreservation method?
