Cryopreservation of Atlantic cod (Gadus morhua) sperm in large‐volume straws: applications for commercial production and gene banking

In our study, we used a full factorial analysis of variance design to examine the effects of diluent [Mounib's sucrose‐based diluent+hen's egg yolk (EY) and Hanks' balanced salt solution (HBSS)+EY], freezing rate (−2.5, −5.0 and −7.5 °C min−1) and thawing rate (2.5, 5.0 and 7.5 °C min−1) on motility and velocity of Atlantic cod sperm cryopreserved in 2.5 mL cryogenic straws. We found that post‐thaw sperm performance was strongly influenced by the presence of higher‐order interactions of the factors we tested. For all models broken down by diluent, the 2.5 °C min−1 thawing rate had the lowest sperm motility recovery index. Mounib's sucrose‐based diluent+EY had the highest motility recovery index at all thawing rates. Mean per cent motility for fresh sperm (87.7±2.9%) was not significantly different than of sperm cryopreserved using Mounib's sucrose‐based diluent+EY, frozen at −2.5 °C min−1 and thawed at 5.0 °C min−1 (77.1±2.9%). For Mounib's sucrose‐based diluent+EY, velocity was significantly higher with sperm thawed at 7.5 °C min−1, than sperm thawed at 2.5 °C min−1, while thawing rate had no effect for HBSS+EY. Our findings have implications for cod mariculture and aiding in conservation efforts for a dominant marine fish species.