The effect of cryopreservation of semen from whitefish (Coregonus lavaretus) and northern pike (Esox lucius) using a glucose-methanol extender on sperm motility parameters and fertilizing ability

The objectives of this study were to determine the specific characteristics of sperm motility and fertilization rates of whitefish (Coregoninae subfamily, Salmonidae, Salmoniformes) and northern pike (Esocidae, Esociformes) in response to cryopreservation using a glucose-methanol extender, which has recently been successfully used for salmonid species. The mean post-thaw sperm motility was 69% for northern pike and 53% for whitefish. Fertilization trials with cryopreserved sperm yielded very high hatching rates for northern pike (79-89%) and for whitefish (54-56%), and these results were similar to those using fresh semen controls. This is the first report demonstrating that the fertilizing ability of cryopreserved northern pike and whitefish semen is similar to that of fresh semen when a sperm:egg ratio as low as 1.5 × 105:1 and 3 × 105:1 was used for northern pike and whitefish, respectively. However, different responses of sperm to the same cryopreservation procedure were observed; therefore, additional studies are required to determine whether the mechanisms underlying of that phenomenon are species-specific and/or related to environmental conditions. Our cryopreservation procedure is applicable not only for salmonid sperm but also for taxonomically distant fish such as northern pike and, therefore, could be used for ongoing northern pike and whitefish conservation and aquaculture efforts. Further studies should focus on the optimization of cryopreservation procedures in order to achieve large-scale fertilization and should aim at defining the minimum efficient sperm:egg ratio for cryopreserved sperm.