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Three cryoprotectants dimethyl sulphoxide (DMSO), propylene glycol (PG) and glycerol, two diluents (sucrose‐ and saline‐based), two sperm collection times, two freezing rates and three times between thaw and activation (0, 30 and 60 min) were tested in order to develop a protocol for the cryopreservation of sperm of haddock Melanogrammus aeglefinus and Atlantic cod Gadus morhua . The faster freezing rate resulted in extremely low post‐thaw motility in comparison to the slower freezing rate, which was successful for sperm from both gadids. In both cases, the use of PG resulted in significantly higher post‐thaw sperm motility‐recovery indices than with DMSO or glycerol, which did not differ significantly from one another. Diluent had no effect on post‐thaw sperm motility for Atlantic cod or haddock. Sperm collected at the end of the spawning season tended to have reduced post‐thaw motility compared to that collected 2 weeks after the start of spawning. A 30 min delay between thaw and activation of haddock and Atlantic cod sperm resulted in a significant decrease in sperm motility. When PG was used as cryoprotectant, sperm motility continued to decrease between 30 and 60 min post‐thaw. With DMSO or glycerol as cryoprotectant, motilities were already very low after 30 min post‐thaw and did not decrease any further after 60 min. Cryoprotectant, diluent and time between thaw and activation had no effect on mean or maximum sperm swimming speeds for either Atlantic cod or haddock sperm. Fertilization success for haddock eggs, like sperm motility, was higher with PG‐frozen sperm than DMSO‐ or glycerol‐frozen sperm. These results constitute the first reported successful cryopreservation of haddock sperm and improve on previous methods used to cryopreserve sperm from Atlantic cod.
Rideout et al. (Fri,) studied this question.