Effects of Cryopreservation on Morphology and Viability of Sperm and Larvae of Atlantic Cod, Gadus morhua L.

The effects of cryopreservation on the viability, morphology and capability of spermatozoa in Atlantic cod, Gadus morhua L., were studied. The sperm was cryopreserved in straws using Hanks' balanced salt solution, hens' egg yolks and glycerol in the vapor of liquid nitrogen. Straws of cryopreserved sperm were stored in liquid nitrogen and thawed in seawater (35 C) for 8 sec before use. The motility of cryopreserved sperm was low (range 819%) compared to motility before freezing (range 6976%). The fertilization rate (range 9495%) in control groups using fresh sperm was significantly higher (P < 0.05) than in test groups (range 4872%). In cryopreserved sperm, a relatively high percentage (range 8293%) of the spermatozoa had changes in morphology. Many spermatozoa had no mitochondria; when mitochondria were present, the observed number varied from one and five in cryopreserved spermatozoa, and from two and seven in noncryopreserved spermatozoa. In groups where cryopreserved sperm was used, the hatching rate was lower (range 1838%) than in control groups (range 4163%), indicating higher mortality during embryonic development. Paternal effects on progeny performance were noted in the proportion of abnormalities but no negative effects were identified in newly hatched larvae produced using cryopreserved sperm.