Application of sperm cryopreservation to hatchery practice and species conservation: A case of the Adriatic grayling ( Thymallus thymallus )

Sperm cryopreservation was successfully applied to the culture of the Adriatic grayling in the Soča river basin in Slovenia whose stocks have been affected by introgressive hybridization with non-native grayling from the Danubian drainage. Sperm was collected from wild males at the spawning sites and cryopreserved while fin clips of the same individuals were subjected to genetic analysis using molecular markers. Sperm samples from individuals having more than 95% of markers characteristicof the Adriatic genotype were thawed and used for fertilization of eggs from previously selected Adriatic grayling females. The hatched progeny is currently grown as a future broodstock or has been stocked into the wild. The present study presents the possibility of relatively short-term (2-6weeks) storage of cryopreserved sperm as an alternative to long-term gene banking.