Effect of methanol concentration and thaw rate on the viability and fertility of cryopreserved Arctic char, Salvelinus alpinus (L.), spermatozoa

In two trials, Arctic char (Salvelinus alpinus) semen was frozen in 0.5 mL straws using extenders consisting of 0.3 M glucose and 10%, 12.5% or 15% methanol. Cryopreserved semen was thawed by immersing straws in 25°C water for 17 s (11.6°C s-1) or in 5°C water for 60 s (3.3°C s-1). The viability of the frozen-thawed semen was measured by determining post-thaw motility and sperm membrane integrity. Two fertility trials were also conducted. There was no effect of trial or thaw rate on post-thaw sperm viability or fertility. Use of 15% methanol in the extender resulted in the highest overall percentage of sperm motility and fertility. Use of 12.5% methanol as a cryoprotectant resulted in a higher per cent post-thaw motility and a lower percentage of dead cells than did 10% methanol. Thus, levels of methanol higher than the commonly used 10% are beneficial for cryopreserving Arctic char sperm.