Evaluation of long-term cryostorage on sperm function and fertility of brown-marbled grouper (Epinephelus fuscoguttatus)

Cryopreservation of fish semen is a valuable technique for reproductive management in aquaculture. The aim of this study was to evaluate the effect of long-term storage in liquid nitrogen on post-thaw sperm functional parameters of brown-marbled grouper (Epinephelus fuscoguttatus). Samples were cryopreserved in a simple freezing medium (10 % DMSO + 0.3 M Glucose), sperm quality parameters were assessed at different storage periods (one month, one year, 2 years and 3 years). Our results indicated that cryostorage periods had a significant effect on the quality of frozen-thawed spermatozoa. Compared with fresh semen, cryopreserved sample was characterized by an overall decline in motility, viability, mitochondrial membrane potential (MMP), ATP content and increased level of lipid peroxidation with the storage time going on. For the analyzed quality parameters, there were no significant differences in storage time cryopreserved over one month. After 3 years of storage, frozen sperm still showed relatively high total motility, viability and MMP (all over 80 %), yielding acceptable fertilizing capacity close to that of fresh sperm. Therefore, it can be concluded that brown-marbled grouper sperm could be effectively cryopreserved for at least 3 years. The results of this study would be helpful to optimize gamete management in routine hatchery practices.